1 ;n82 n. s no. 83 Historic, archived document Do not assume content reflects current scientific knowledge, policies, or practices UNITED STATES DEPARTMENT OF AGRICULTURE LIBRARY BOOK NUMBER I En82B 391141 n.s.,no.83 USOA National Agricultural library MAI Building 103Q1 Baltimore Blvd. MO 20705-2351 inn U. S. DEPARTMENT OF AGRICULTURE, BUREAU OF ENTOMOLOGY— BULLETIN No. 83, Part I. L. O. HOWARD, Entomologist and Chief of Bureau. *(?. Eastern Larch Beetle. X Don-las Fir Beetle 14. Eastern Spruce Beetle. 15. TCngelinaim Spruce fcetle. Hi. Alaska Spruce Beetle. 17. Sitka Spruce Beetle 18. Redwinged Beetle. [opk. 19. Lodgcpole Beetle. I'.lack Turpentine Beetle. Red Turpentine Beetle. 24. Guatemala Beetle 24. adjunclu Classification of the Genus Dendroctonus, Showing Technical and Commfl Names and Species Numbers. This diagram will enable the reader to refer at once to the technical and common nam of any species number mentioned ill the text and will show at a glance the positu and relations of the divisions, subdivisions, sections, subsections, scries, and speci into which the genus is divided. Bui. 83, Part I, Bureau of Entomology, U. S, Dept. of Agrici t I A t i» c2 B a? I C a b4 D 02 fl} '3 f-i O) CD cc a: rC3 O r 1. brevicomis 2. barberi He 3. convexifroi 4. frontalis Z 5. arizonicus 6. mexicanus 7. parallelocc 8. approxima 9. monticolx 10. ponderoste 11. jeftreyi Ho 12. simplex Le 13. pseudotsug 14. piceaperda 15. engelmann 16. /-omiZ/'s H 17. obesus Mai 18. rufipennis 19. initrruiiaii; 20. punctatus 21 . mica us Ku 22. terebrans ( 23. valens Lee Position doubtful— 24. adjunct™ Classification of the Genus Dendroctonu? Names and Specie This diagram will enable the reader to refer at c of any species number mentioned in the texi and relations of the divisions, subdivisions into which the "genus is divided. U. S. D. A., B. E. Bui. 83, Parti. F. I. I., October 11, 1909. PRACTICAL INFORMATION ON THE SCOLYTID BEETLES OF NORTH AMERICAN FORESTS. I. BARKBEETLES OF THE GENUS DENDROCTONUS. By A. D. Hopkins, In Charge of Forest Insect Investigations. INTRODUCTORY. The first part of this bulletin supplements Technical Series No. 17, Part I, of this Bureau, in giving facts of practical interest and importance on a group of barkbeetles which contains the most destructive enemies of the principal coniferous forest trees of North America. To avoid the too frequent repetition of technical and common names in the text or in footnotes, the species number is used, referring to the corresponding number in a classified list of technical and com- mon names in Plate I. The list of publications, in which references are to be found to some economic feature of one or more species, is arranged in chrono- logic instead of alphabetic order, so that the reference in the text is to the year in which the particular article referred to was pub- lished, as well as to the author's name. A more extensive bibliog- raphy is found in Technical Series No. 17, Part I. HISTORICAL. The name "Dendroctonus," which means killers of trees, was pro- posed in 1836 by Dr. W. F. Erichson to designate a genus of beetles which was then represented by two described species — the European spruce beetle (No. 21) (see Plate I) and the black turpentine beetle (No. 22). Between that time and 1897 ten more North American species, as at present recognized, were added, one (No. 18) by Kirby in 1837, one (No. 17) by Mannerheim, 1843, one (No. 23) by Le Conte, 1860, one (No. 4) by Zimmerman in 1868, two (Nos. 12 and 20) by Le Conte in 1868, one (No. 7) by Chapuis in 1869, one (No. 1) by Le Conte in 1876, one (No. 8) by Dietz, 1890, and one (No. 24) by Blandford in 1897. The writer has added twelve (Nos. 2, 3, 5, 6; 89535— Bull. 83, pt. 1—09 2 l2 THE SCOLYTID BEETLES. 9, 10, 11, 13 to 16, and 19) Xorth American species, but none has been added from any other part of the world. Therefore the genus is now represented by 23 species from North America and one from Europe. The European species was early recognized as a destructive enemy of spruce and other coniferous trees, and much information has been published relating to its habits, life history, distribution, and methods of control. Previous to the year 1891 only two species had been recognized in this country as depredators on forest trees. The black turpentine beetle had been referred to by Olivier, 1795, and the red turpentine beetle by Harris, 1826 to 1862, and by other writers, as enemies of pine, and the eastern spruce beetle (Xo. 14), under the name of another species (Xo 18), was recognized as a destructive enemy of the spruce in the northeastern United States and southeastern Canada and was the subject of special investigations and reports by several authors. In 1891 the writer found that the southern pine beetle (Xo. 4) was the cause of the death of pine and spruce timber over extensive areas in West Virginia and adjoining States, and it was the subject of special investigations and reports (Hopkins, 1892 to 1899). It was also mentioned in publications by Chittenden (1897), Schwarz (1898), and others. In 1899 the writer made observations on the destructive habits of the western pine beetle (Xo. 1), the red turpentine beetle (Xo. 23), the mountain pine beetle (Xo. 9), and the Douglas fir beetle (Xo. 13), and observed the habits of the Sitka spruce beetle (Xo. 17). In 1900 the destructive work of the eastern spruce beetle (Xo. 14) in northwestern Maine was investigated, and in 1901 investigations were made on the Black Hills beetle (Xo. 10) and its depredations in the Black Hills of South Dakota were investigated. Since July, 1902, many trips have been made by the writer to different sections of the country in general, and special investigations made of the work of one or more of the species of this genus, as noted further on, under "Basis of information/' following the account of each species. Messrs. J. L. Webb, H. E. Burke, and W. F. Fiske. assistants in forest insect investigations, working according to the plans and under instructions of the writer, have given special atten- tion to the study of the seasonal history, habits, etc., of the species found during their active field work. Mr. Webb spent two seasons (1902 and 1906) in the Black Hills National Forest, principally in the study of the Black Hills beetle (Xo. 10) and its work and in conducting experiments with trap trees: one season (1904) in the San Francisco National Forest, giving special attention to species 2, 3, and 8, and one season (1905) in central Idaho, studying the western pine beetle (Xo. 1) and in conducting THE GENUS DENDKOCTONUS. 6 experiments with trap trees. He also spent the season of 1906 in the Black Hills to complete the investigations on the Black Hills beetle and the season of 1907 in the national forests of southern New Mexico and Arizona in general field work. Mr. Burke spent three seasons (1903, 1904, and 1905) in western and northwestern Washington in general forest insect investigations, and made observations on the Sitka spruce beetle (No. 17) and the Douglas fir beetle (No. 13). He also made special trips to Idaho and South Dakota in 1904 to determine certain facts relating to the west- ern pine beetle (No. 1) in Idaho and the Black Hills beetle (No. 10) in South Dakota. In 1906 he spent the greater part of the season in the Yosemite National Park, under instructions to make special studies of the mountain pine beetle (No. 9), the western pine beetle (No. 1), and the red turpentine beetle (No. 23), and in 1907 he made observations on the southwestern pine beetle (No. 2), the Black Hills beetle (No. 10), and other species in the forests of Utah. Mr. Fiske gave special attention to the investigation of the south- ern pine beetle (No. 4) and its work, experiments with trap trees, etc., during his general investigations of forest insects in the South Atlantic and Gulf States during the seasons of 1903, 1904, 1905, and 1906, and studied the seasonal history and habits of the black turpentine beetle (No. 22) and the red turpentine beetle (No. 23) — the latter in the mountains of North Carolina. In the fall of 1906 he made observations on the eastern larch beetle (No. 12) and the redwinged pine beetle (No. 18) in northwestern Michigan, and in the spring of 1907 he made observations on species 4 and 22 in Texas and on species 2, 3, 5, 8, 13, 15, and 23 in southern New Mexico. This field work by the writer and his assistants has resulted in the accumulation of a mass of material in specimens and notes which has served as a basis for the preparation of this part of the bulletin. Considerable material has also been received from officials of the Forest Service, together with information in regard to the location and extent of depredations, and from owners of private forests and other correspondents in different sections of the country who have notified us of troubles affecting the timber and have responded to our requests for specimens and detailed information in regard to the character and extent of the depredations. DESTRUCTION CAUSED BY THE BEETLES. The results of our investigations have clearly shown that some of the species of this genus of beetles are the most destructive enemies of the coniferous forest trees of North America. As examples, we have only to cite the well-known depredations by the eastern spruce beetle (No. 14) in the northeastern United States and New Bruns- 4 THE SCOLYTID BEETLES. wick during the past century (Hopkins, 1901a), the widespread destruction of pine and spruce by the southern pine beetle (Xo. 4) in West Virginia and Virginia in 1891 and 1892 (Hopkins, 1899a), the destruction of a large percentage of the timber in an entire Xational Forest by the Black Hills beetle (Xo. 10) within the past ten years (Hopkins, 19026 and 1905), and the depredations by the western pine beetle (Xo. 1) in Idaho, Oregon, and California (Webb, 1906), and by the mountain pine beetle (Xo. 9) in Wyoming, Montana, Idaho, Oregon, Utah, and California noted in the present paper. CHARACTER AXD EXTEXT OF DEPREDATIOXS. Living healthy trees are attacked by swarms of the adult beetles^ which enter the bark on the mam trunk and excavate their egg galleries for a distance of a foot or more through the inner, living bark. This weakens the vitality of the tree, and in addition the larvae hatching from the eggs mine through and destroy the bark intervening between the egg galleries, thus completely girdling the trees and causing their death. The amount of timber killed in this manner during the past century has been enormous. That known to have been killed by these beetles in West Virginia, New England, and the Black Hills Xational Forest alone amounts to many billions of feet of the best pine and spruce, to say nothing of the less conspicuous depredations each year scattered through the forested sections of the Rocky Mountain, Cascade, Sierra, and Coast regions, and of the Southern States. Very conclusive evidence has also been found that some of the great denuded areas in the Rocky Mountains region supposed to have been caused by forest fires were primarily caused by one or more species of Dendroctonus. From our present knowledge of the facts and evidence it is probable that if the timber destroyed by these insects in the United States during the past fifty years were living to-day its stumpage value would be more than $1,000,000,000. POSSIBILITIES OF CONTROL. The results of our investigations, experiments, and practical demonstrations make it clear that wherever private forests or State or Xational forests are under organized management for fire pro- tection and economic utilization the control of these insects is often a less difficult and less expensive problem than that of controlling forest fires. In fact, wherever there is a sufficient demand for the timber, and where facilities for the utilization of the trunks of the infested trees within a specified time exist, the desired control may often be brought about and maintained practically without cost or even at a profit, especially if the action be taken before the depre- dators have spread over extensive areas. THE GENUS DENDROCTONUS. 0 If, when first discovered, the depredations of the beetles have already involved an extensive area, or if they are neglected until a large percentage of the timber is killed, their artificial control will be as difficult and expensive as that of a neglected forest fire. Further- more, if the depredations occur in an inaccessible section of the forest or where the conditions as to labor and other facilities are unfavorable for necessary action, nothing more can be done toward the control of the beetles than under the same conditions in con- trolling a fire. But with the rapid extension of modern forest management, lumbering operations, and working plans into the principal public and private forests, and especially with the adoption of fire-control regulations under an organization of fire patrols and rangers, there will be no excuse for neglecting the insects. THE BEETLE PROBLEM AS IMPORTANT AS THE FIRE PROBLEM. In certain sections of the country and in certain National Forests where the more destructive species of beetles are present and a constant menace to the standing timber, the beetle problem is undoubtedly as important as the forest-fire problem, and therefore demands the adoption and organization of beetle-control work, which, with little or no additional force and equipment, can be conducted by fire patrols and forest rangers. The evidence of destructive beetle work is not quite as distinct as is the evidence of fire, and can not be seen quite so far, but a clump of yellow-top or red-top trees can be seen for a long distance, and upon closer inspection the pitch tubes and boring dust on and around the trunks of living trees are sufficient danger signals to demand that the required action be taken to prevent widespread depredations. There is one great advantage in the requirements for successful beetle control over those for fire control, viz, there is usually a period of six to ten months in which to utilize or otherwise dispose of the affected timber to destroy the broods of beetles in the bark, while a fire requires immediate attention. DISTINCTIVE CHARACTERS OF THE GKENTJS.a The beetles of the genus Dendroctonus (see figs. 1, 2, 3, etc.) are distinguished in the adult stage by their cylindrical, somewhat elongate to stout bodies, broad and prominent heads, nearly round to oblong-oval and transversely placed eyes behind the base of each antenna, the last with an elongate, clublike basal joint (scape) followed by 5 short joints (funicle) and terminated by a broad club which is thickened at the base and flattened toward the apex, and a See also Technical Series No. 17, Part I, for technical descriptions of genus, species, etc. :he scolytid beetles. THE GENUS DENDROCTONUS. ( has three to four closely connected joints denned by curved lines. The front of the head has a distinct middle elevation toward the base of the mandibles, called the epistomal process (see figs. 2, 3). The pronotum is slightly more than half to slightly less than half as long as the elytra, which have fine to coarse rugosities between rows of obscure to distinct punctures. The diagram, Plate I, gives the technical and common names of the beetles of the genus, and shows how the different species fall into natural primary and minor divisions according to certain structural characters and peculiar habits. ADULT CHARACTERS. In the species of Division I the pronotum is somewhat elongate and as broad as the elytra, and in those of Division II the pronotum is shorter and is usually narrower than the elytra. In species 1 to 8 (subdivision A) the body is somewhat slender, and the pronotum is but slightly narrowed toward the head, which in all but species 3 (comprising subsection b1) has a frontal groove and two frontal elevations. In species 1 and 2 (section a1) the elytra are without long hairs, while in species 3 to 8 (section a?) there are long hairs toward and on the declivity. In species 9 to 11 (subdivision B) the body is stouter and the pronotum is distinctly narrowed toward the head, which is without frontal groove or elevations. In species 9 and 10 the punctures of the pronotum are moderately coarse and deep, while in species 11 they are shallow and usually fine, with the surface more shining. In species 12 to 21 (subdivision C) the punctures of the pronotum are of irregular size, while in species 22 and 23 (subdivision D) they are regular. In species 12 and 13 (section a3) the striae of the elytral declivity are deeply impressed, and the interspaces are convex, while in species 14 to 21 (section a4) the striae are but slightly or not at all impressed and the interspaces are flat or but slightly convex. In species 14 to 19 the striae of the elytral declivity have obscure to fine punctures, while in species 20 and 21 the strial punctures are coarse and distinct. Species 22 and 23 are easily distinguished by their large size, evenly punctured pronotum, which is subelongate and almost as broad as the elytra, and by the very large and prominent head. EXTERNAL SEXUAL CHARACTERS. In species 1 to 8 (subdivision A) the females are distinguished by a transverse, rather broad, elevated ridge across the pronotum near the anterior margin, moderately broad head, and moderately large mandibles. The males are without the transverse ridge across the THE SCOLYTID BEETLES. ^C UUTTI Sternum I- ■ - Episternum —Exocoxal piece Epimervm ~~ Sternellar area Coxa Sternum Episternum Median line Sternellar piece . — --Coxa ■-Epimemm TnterGoxal process '3d suture Unites re sutu o s Fig. 2.— The red turpentine beetle. Adult, ventral aspect, greatly enlarged: a, Sternellar area. (Author' illustration.) THE GENUS DENDROCTONUS. pronotum; but the frontal groove and tubercles are usually more dis- tinct, the head broader, and the mandibles stouter. In species 9 to 11 (subdivision B) the females have the declivity of the elytra somewhat flattened and shining and the interspaces with Fig. 3.— The red turpentine beetle. Adult, lateral aspect, greatly enlarged: a, Pleural clavicula; b, pregena. (Author's illustration.) small granules and sometimes punctured. In the males the declivity is more convex, the interspaces have coarser granules, the head is broader, and the mandibles are stouter. 10 THE SCOLYTID BEETLES. In species 12 to 21 (subdivision C) the sexes are easily distinguished by the differences in the declivity of the elytra. In the females the stride are more distinctly impressed and the interspaces more convex and roughened. In the males the stride are much less or not at all impressed and the interspaces are shining, smooth, and often punctured. In species 12 and 13 (section a3) the striae are deeply impressed in both sexes; but in species 14 to 21 (section a4) they are rarely impressed in the males. * In species 22 and 23 (subdivision D) the sexes are less distinctly defined by external characters. In the. females the antennal club is broader, stouter, and more compressed; the head is narrower and the mandibles are smaller, while the reverse is true in the males. THE EGG. The eggs of the majority of the species have been observed and apparently show no differences except in relative size, corresponding with the size of the adults. They are slightly oblong, rounded at the ends, pearly white, and shining. THE LARVA. The larva (fig. 4) is a stout, cylindrical, yellowish- white, footless grub with a yellowish shining head. The body is deeply and closely wrinkled, as shown in the figure. In species 1 to 11 the dorsal surface of the 8th and 9th abdominal segments are smooth, without chitinous plates, and the ventral pro- thoracic lobes are more or less prominent. In species 1 and 2 the front is without a median elevation. In species 3 to 7 the front has a more or less rounded convex elevation. In species 9 to 11 the front has a transverse roughened elevation, slightly more elevated toward the sides. In species 12 and 13 the dorsal surface of the 8th and 9th abdominal segments is without chitinous plates. In species 14 to 23 one or both have distinct plates. In species 14, 15, 17, and 19 the 8th and 9th abdominal plates are without prominent spines. The, frontal elevation, when present, is transverse. The larva? of species 16 to 18 and 19 have not been observed. Species 21 has a roughened plate on the 9th segment, but none on the 8th. In species 12 the front is without a median elevation, but in spe- cies 13 there is a distinct transverse, rugose, median elevation, more elevated toward the sides. THE GENUS DENDROCTONUS. 11 In species 14, 15, and 19 the front has a transverse elevation, but in 17 it is absent or indistinct. In species 22 and 23 the dorsal plates of the 8th and 9th segments have prominent spines, and the front of the head is without elevations. THE PUPA. The pupa (fig. 5) is of the general color of the larva, but is of the general form and size of the adult, with the legs and wing pads folded beneath the body and the abdominal segments exposed. The 9th segment has two prominent fleshy spines, and the other segments are 12 THE SCOLYTID BEETLES. with or without dorsal, lateral, and pleural spines, which vary in size among the different species from very smooth to quite coarse and prominent. In species 1 to 5 and 8 to 11 the vertex or front of the head is grooved, with prominent or small fleshy seines situated at each side of the groove. The pupae of species 6 and 7 have not been observed. In species 1 to 5 and species 8 the elytral pads are smooth and the abdominal segments have small lateral spines or tubercles. In species 1 and 2 the vertex of the head is faintly grooved, the spines are small and widely separated, and the front and middle femora are without apical spines or granules. In species 3 the vertex is faintly grooved, the spines are very small, and the front and middle femora have apical granules. In species 4, 5, and 8 the vertex is broadly grooved, the spines are moderately small and widely separated, and the front and middle femora have small apical tubercles. In species 9, 10, and 11 the elytral pads are roughened, with sparsely placed granules. The head has the vertex deeply grooved and the spines prominent, and the abdominal segments have very long lateral spines. In species 9 and 11 the front and middle femora have two apical spines each, while in species 10 they have one each. In species 12 to 23 the vertex is either faintly impressed or convex, with an acute granule at each side and one or two on each side on the front. The elytral pads are smooth, and the abdomen has more or less prominent lateral spines. In species 12 and 13 the vertex of the head is faintly impressed or grooved, and the front and middle femora are without granules or spines. In species 14 to 23, so far as observed, the vertex is convex, and the femora have small apical granules. EGG GALLERIES, LARVAL MIXES, AND PUPAL CELLS. (See figures of work.) In species 1 to 11 the egg galleries are winding to straight, with individual larval mines concealed or exposed in inner bark and with the pupal cells either in the outer or in the inner bark. In species 1 to 8 the egg galleries are winding, nearly transverse to oblique; the larval mines short, not in groups; and the pupal cells are in the outer bark. In species 1, 2, 5, 6, 7, and 8 the larval mines are concealed, while in species 3 and 4 they are exposed in the inner bark. In species 9 to 11 the egg galleries are longitudinal, slightly wind- ing to straight. The larval mines are short and usually in groups, THE QENUS DENDEOCTONUS. 13 and both the pupal cells and larval mines are exposed in the inner bark. In species 12 to 23, so far as observed, the egg galleries are longitu- dinal, straight to slightly winding, with the larval mines either in groups or connected, or they form a broad common chamber, and all are exposed in the inner bark. The pupal cells are located at the ABDOMEN on; t? "is ss- V ' p ^ < jti . 2. s p. -^ r end of the larval mines or in the larval chambers and are usually exposed. In species 12 to 13 the egg galleries are straight or slightly winding, sometimes branched, the larval mines are in groups and exposed in the inner bark, and the pupal cells are exposed or concealed. 14 THE SCOLYTID BEETLES. In species 12 and 13 the egg galleries are long, longitudinal, straight, or slightly winding, sometimes branched, and moderately broad; the larval mines are long, independent of each other from the start, winding, and more or less regular. In species 14 to 21, so far as observed, t-he egg galleries are broad, moderately long, straight, irregularly branched at terminals, and usually with an inner gallery through the packed borings of the finished egg galleries; the larval mines are long, connected toward the egg gallery, independent and irregular, or forming a broad larval chamber. In species 14, 15, and 17 the larval mines are connected toward the egg gallery and separated toward the middle and outer ends. In species 19 and 20 the larvse excavate a common or social cham- ber, sometimes with independent mines extending from the edges. In species 22 and 23 the egg galleries are broad to very broad, short to very long, and straight or slightly winding, and the larval mines form very large common chambers, with the pupal cells in the chamber or at the ends of short independent mines extending from the edge of the chamber. DISTRIBUTION. The distribution of the species of Division I is from the South Atlantic States to Mexico and Central America, and northward into the Rocky, Sierra Xevada, and Cascade mountains to British Columbia. Species 1 occupies the region of the western yellow pine west of western Montana and southern Idaho, southward to Santa Barbara County, Cal., while species 2 occupies the Rocky Mountains region south of central Colorado and central Utah, into southern California and northern Mexico. Species 3, 5, and 8 occupy practically the same region as species 2, while species 4 occupies the region of yellow pine, loblolly pine, and longleaf pine south of Pennsylvania and westward into Texas, and species 6 and 7 occupy the pine regions of the mountains of southern Mexico. Species 9 occupies the region of silver pine, lodgepole pine, and sugar pine north of Colorado and Utah and westward into the Sierra Xevada and Cascade mountains. Species 10 occupies the region of the Rocky Mountain variety of the western yellow pine and limber pine above an altitude of 6,000 feet, from western South Dakota southward through Wyoming, Colorado, and Utah to southern Xew Mexico and Arizona, while species 11 occupies the Jeffrey-pine region from the mountains of San Bernardino County, Cal., to northern California, and probably into Oregon. Plate II. ll^>pfitt ^JSffir^T^ffl 0^%miM ■^Bi;:iy;-% ..... ., , -^-y ' "^^^^A%^ / j-; . ' :'"'"\ \&--<% :;*„!* T" ' ^\^Wl''i '["" 'pSf riiC\i'\ 'W ,„„ § ^'^i*"-^^r,:?^^^-""i i "'"":Sl.i"t-"""/Jx ct^ '"^■S^fegy "r^w^a/^J.^Pf ' ■'" • .■•■• J««g ~ -; '^^'''Ml ,„.„,., „ , , \ ' ^stsr^1 11 f S^fiO^I "-'^ ■ " ■; / TlFP~ ■'■Y-f te *"*"V ** T ^_£\ • -"- . h i Map of the World, Showinq Distribution of the Genus Dendroctonus. (Aut THE GENUS DENDKOCTONUS. 15 The species of Division II range from Guatemala northward to Alaska, eastward to the Atlantic coast, and across northern Europe and Russia into Siberia. Species 12 occupies the regions and sections of eastern larch from northwestern West Virginia, northward and westward, while species 13 occupies the region of the Douglas fir, bigcone fir, and western larch from southern New Mexico and Arizona to Ventura County, CaL, and northward into British Columbia. Species 14 occupies the region of red spruce from the high moun- tains of Pennsylvania northward and from New Brunswick to north- western Michigan, and probably northwestward to the 100th meridian. Species 15 occupies the region of Engelmann spruce from the white spruce in western South Dakota westward, and north of southern New Mexico. Species 16 occupies the white-spruce region in Alaska, and species 17 the Sitka-spruce region from southern Oregon to Sitka. Species 18 occupies the Lake Superior region; species 19 the region of lodgepole pine from central Colorado northward probably into British Columbia ; species 20 the regions of red spruce from the moun- tains of West Virginia into New York; while species 21 occupies the spruce and pine regions north of central Europe in Denmark and through Russia to eastern Siberia. Species 22 occupies the region of pitch pine, Virginia pine, yellow pine, loblolly pine, and longleaf pine from Long Island, New York, east of the Allegheny Mountains, southward to Florida and Texas, and west of the mountains from the Little Kanawha River probably through Kentucky and Tennessee, while species 23 occupies the regions of pine timber from the Atlantic to the Pacific north of the South Atlantic and Gulf States and south into the mountains of Guatemala. Species 24 is described from Guatemala. The distribution maps (figs. 11, 14, 17, etc.) show the known and probable ranges of each species, the known range being indicated by large dots and the probable range by small 'dots. The distribution of the genus is shown on a map of the world (PI. II.) HOST TREES. In Division I the species confine their attack to pine and spruce, but principally to the pines. Species 1 confines its attack to the western yellow and sugar pine, and is a destructive enemy of both. Species 2 attacks the western yellow pine, but, so far as observed, is much less destructive than its northern and western neighbor. It has also been found in the Doug- las fir, but this is evidently an abnormal habit. 16 THE SCOLYTID BEETLES. Species 3, 5, and 8 are usually associated with No. 2 in the western yellow pine, but none of them has been especially destructive, al- though independently or collectively they are capable of being so. Species 4 attacks all of the pines and spruces within its range, and while it caused widespread devastation in its northern range during 1891 and 1892 its destruction of timber within its southern range, so far as observed, is comparatively moderate. The species of subdivision B are the most destructive insect enemies of western pine forests. Species 9 attacks the western white pine, silver pine, sugar pine, lodgepole pine, and western yellow pine, and is exceedingly destructive in certain localities throughout its range, especially to the silver pine, sugar pine, and lodgepole pine. Species 10 attacks the Rocky Mountain variety of the western yellow pine, limber pine, white spruce, and Engelmann spruce, but confines itself principally to the yellow7 pine and is exceedingly destructive, as has been conclusively demonstrated in the Black Hills Forest Reserve of South Dakota and in numerous localities in Colorado. Species 11 attacks the Jeffrey pine and western yellow pine, but principally the former, to which it is quite destructive. The species of Division II attack pines, spruces, larches, and Douglas fir, and some of the species are very destructive to living timber. Species 12 confines its attack to the eastern larch. There is no positive evidence that it is primarily destructive to living timber, but it evidently contributes to the death of trees defoliated by the larch worm. Species 13 confines its attack principally to the Douglas fir, but is also found in the bigcone spruce and western larch. In the northwestern section of its range this species is not especially destructive, but in its eastern and southern range it is very destruc- tive to the Douglas fir. Species 14 attacks the red spruce, black spruce, and white spruce, and from time to time during the past century it has been exceed- ingly destructive to the red spruce in Maine and Xew Brunswick. Species 15 attacks the Engelmann and evidently the other spruces of the Rocky Mountain region. There is conclusive evidence that it has caused widespread devastation of matured spruce during the past fifty years, and it is now quite aggressive in some localities. Species 16 has been found in the white spruce, but nothing more is known of its habits. Species 17 attacks the Sitka spruce, but there are no records to indicate that it has been primarily destructive to living timber. Species 18 lives in the white pine, but nothing further is knowm of its habits. Species 19 attacks living lodgepole pine and Engelmann spruce, but it is not known whether or not it is primarily destructive. Species 20 wTas found in the living bark on a red-spruce stump in West Virginia, which is all that is known of its habits. THE GENUS DENDROCTONUS. 17 Species 21 is recorded as attacking spruce and pine principally, and as sometimes attacking larch, and fir (Abies), and is recognized as a destructive enemy. Species 22 attacks the different species of pine within its range and has also been found in spruce. It is sometimes destructive to living trees, but more often is simply injurious to the base of the trunks in causing basal scars. Species 23 attacks all of the pines and is some- times found in spruce and larch. It rarely causes the death of trees but causes serious damage to the base of living trees, resulting in the common defect known as basal scars and fire wounds. EVIDENCES OF ATTACK. In all of the species the first evidence of attack on living trees is the presence of pitch tubes on the trunks, mixed with reddish bor- ings, or the presence of reddish boring dust in the loose bark and around the base of the trees. Later the fading, yellowish, or reddish condition of the foliage is conspicuous evidence of the barkbeetles' destructive work. Successful attacks by species 1 to 8 are followed by a rapid death of the trees. The leaves fade in a month or two and turn yellow and reddish before winter. Successful attacks by species 9 to 11 are fol- lowed by a slow death of the trees. While tlfe trees attacked during the summer will have the bark on the trunks killed, the leaves will not turn yellow until the following May. Attacks by species 12 and 13 are not as a rule indicated by pitch tubes, but the reddish boring dust in the crevices of the bark, in the loose bark, and around the base of the trunk of Douglas fir or larch is quite conclusive evidence of their presence. Douglas fir attacked in the summer will have the leaves fading and turning pinkish in the fall and winter, and reddish in the spring. The leaves on the larch probably fall before they fade, although some of them may remain on the trees after the normal time for them to fall. In species 14 and 15, pitch tubes and red boring dust, mixed with resin, on the trunk and around the base, are evidences of attack. The trees attacked in the early summer will shed their green needles before fall. Those attacked later in the summer will have the bark on the trunks killed before winter, but the leaves may remain green until growth starts in the spring, when they will fall. Thus in May and June one often finds the ground beneath the infested trees covered with the green needles. After the leaves have fallen the bare twigs will cause the tops of infested trees to present a reddish appearance. Species 18 to 20 appear to confine their attack to or toward the base of the trees, where large pitch or gum tubes are formed, indi- eating their presence. In Europe, species 21 sometimes attacks the 89535— Bull. 83, pt. 1—09 3 18 THE SCOLYTID BEETLES. trunk at points some distance above the base, where the large pitch or gum tubes indicate their presence. Species 22 and 23 nearly always attack the base of the trees, where the very large pitch tubes and masses of pitch indicate their work. TVhen the main trunk is infested by these species to a sufficient extent to kill the trees, the evidence of infestation is found in the large pitch tubes and yellow foliage of the dying trees. SEASONAL HISTORY. The important features in the seasonal history of these beetles are the hibernation or overwintering of the broods, the beginning of activity in the spring, the emergence and flight of the adults, the beginning and ending of the period of principal attack, the period of larval development, the principal period of transformation from the larvae to the pupoe and adults, the beginning and ending of the period of emergence, and the number of generations annually. Certain features in the seasonal history of all of the species are similar, but as a rule each species or series of closely related ones has peculiarities which are more or less distinctive. A knowledge of these facts, therefore, is of prime importance as a basis for advice relating to the exact species involved in a given trouble and the successful methods of control. The broods of all of the species pass the winter as adults and larvae in the bark of the trees, logs, or stumps attacked during the preceding spring, summer, or fall. All excavate galleries through the inner living bark in which to deposit eggs, and the larvae of all feed on the inner bark; all become more or less active as soon as the weather conditions are favorable in the spring, especially the larvae and overwintered parent adults, the former extending their larval mines and the latter their egg galleries. The principal differences in seasonal history are brought out in the following references to the general features of the different species and in the detailed dis- cussion under each species farther on. In species 1 and 2, under average conditions, there is one complete generation and a partial second during the season of activity. In species 1 the first attack is made during the last week in June and first week in July, and the more advanced broods develop and begin to emerge about the last of August, but are not all out before cold weather. The first eggs of the second generation are deposited about the first of September, but the broods do not develop beyond the larval stage before hibernation begins in October. In species 2 the seasonal history is practically the same as in species 1, except that the attack and subsequent stages begin a month earlier. The attack begins during the last of May, and the advanced broods begin to emerge during the latter part of July. THE GENUS DENDROCTONUS. 19 In species 3 there is but one generation annually in the more advanced broods, while the more retarded ones may pass through two winters before they complete their development and emerge. The adults begin to emerge, attack other trees, and deposit eggs toward the last of June, but the broods do not develop before hiber- nation begins in the fall. Species 4 has two or three generations annually in its northern range. In the intermediate range, represented by Try on, N. C, there are three or four generations, while in the more southern range there may possibly be five generations, with activity continuing during the warmer days of winter. Under average conditions the first attack is made about the middle of May, and under favorable conditions the resulting brood develops to adults and emerges in about sixty clays. Species 5 evidently has a seasonal history similar to species 2 In species 8 there is but one generation annually. The attack begins in June, and the broods do not emerge until the following June to August, or later. In species 9, 10, and 11 there is but one generation annually, and the seasonal history of each is quite similar to that of the others. The first attack is made during the last week in July or first week in August, and the broods do not develop and emerge until the following July and August. In species 12 and 13 there is a single generation annually. The first attack is made in April to May, and the broods emerge the fol- lowing April to July. In species 14 and 15 there is but one generation annually. The first attack is made in June, and the broods do not emerge until the following June to August. In species 17 the attack begins a month earlier. In the European species (No. 21) the first attack is made in May and June, and the broods emerge the following May to August. In species 22 and 23 there is but one generation annually. The attack is made during the first warm days in March to April, and the broods emerge the following March to September, or later. INFLUENCES OF LATITUDE AND ALTITUDE ON SEASONAL HISTORY. The beginning and ending of the hibernating period vary somewhat among the different species, and in each species there is considerable difference at different latitudes and altitudes within its range. Within the area of a given State or section of the country this differ- ence in the beginning or ending of a given period in the seasonal his- tory of a species can be estimated after the date of beginning is deter- mined for a given season in a given locality. In the spring of a given year the average difference in the time of beginning activity, emer- gence, flight, attack, etc., at the same altitude, will not vary much from four days later for each degree north, or four days earlier for 20 THE SCOLYTID BEETLES. each degree south, while at the same latitude there will be a difference of about four days for each 400 feet difference in altitude — four days later for each 400 feet higher, and four days earlier for each 400 feet lower. Thus a difference of 7| degrees of latitude at the same eleva- tion would mean a difference of about thirty davs in the beginning of activity or any other event, depending on a given average tem- perature, while a difference of 3,000 feet in altitude at the same degree of latitude would cause an equal difference in these phenolog- ical events. In the fall of the year the beginning of hibernation and other events will be earlier northward and later southward at localities of the same elevation, or earlier at higher altitudes and later at lower alti- tudes in the same latitude. Of course there are exceptions to these rules, especially in regions like that of California, where remarkably abnormal conditions as to influence of altitude and latitude prevail, as also in the case of southern and northern exposures, sandy dry soils, and wet clayey soils or bogs. In such cases the estimates must be corrected so as to allow for three or four days later for the beginning of activity, etc.. under average colder conditions, or three or four days earlier for average warmer conditions. The best indication of the rate of difference between two localities is found in the average difference in the dates of opening of the buds or flowers of some indigenous species of forest trees com- mon to both localities, and especially of a species of conifer subject to the attack of a given Dendroctonus beetle. A knowledge of the facts relating to this principle is of especial importance as a basis for recommending or executing beetle-control policies, since success depends largely on a Jcnoxdedge of the proper time to begin and end certain timber-cutting or barling operations for tin destruction of the broods of the beetles. When, as is usually the case, the seasonal-history data have been collected at different latitudes and altitudes within the range of the species, the discussion under each species is based on a probable average. But when the data have been collected in one locality the discussion relates to that locality, and the probable differences are esti- mated for other localities. While there is yet much to be determined in regard to the rate of difference between different localities at the same latitude or elevation in the same region and the influence which different latitudes and altitudes exert (in different species, sufficient evidence is at hand regarding some of the species of this genus and the regions occupied by them to warrant certain preliminary conclusions a- a basis for action and further study. V THE GENUS DENDROCTONUS. 21 HABITS. HABITS OF PARENT ADULTS AND OF IMMATURE STAGES. All of the species of Dendroctonus will breed to a greater or less extent in the living and dying bark of stumps and logs, and in injured and weakened trees. Some of them show a preference for trees in weakened condition, while others show a preference for healthy trees. All of those studied, however, have demonstrated their ability to attack healthy trees and kill them whenever the individuals of a species occur in sufficient numbers to overcome the resistance of the tree. The habit of swarming, or of congregating in one locality and concentrating their attack on groups of trees within a forest, is one of the more striking features in the habits of these beetles. The part of a tree selected for the attack varies somewhat in the different subdivisions of the genus. The species that are more destructive to the life of a tree attack the middle to upper portion of the trunk, while those that are less destructive attack the trunk toward the base, or even at the roots. The beetles' power to resist the repelling effects of the resin that flows into the freshly excavated entrances and galleries in the living bark and to dispose of it by forming pitch tubes at the entrances is most remarkable. This alone demonstrates the ability of these insects to overcome the resistance exerted by a living, healthy tree. The manner of excavating the egg galleries and the directions followed in their extension are quite different among the several species and have a different effect on the tree. The almost transverse, very winding, and closely arranged galleries of species 1, 2, 4, 5, and 6 serve to quickly girdle and kill the trees, while the straight, longitu- dinal course and parallel arrangement of those of species 9, 10, 11, 13, and 14 result in a much slower, but none the less certain, death of the tree. RELATION OF HABITS TO SUCCESSFUL CONTROL. The habits of the broods of larvae are of special importance in indi- cating methods of control. In subdivision A the larvae of species 1, 2, 5, 6, 7, and 8 excavate their larval mines through the middle layers of the inner bark, so that they are rarely exposed in the inner bark. Those of species 3 and 4 are exposed, but in all of the species of subdivision A the transformations from the larvae to the pupae and adults are almost entirely in the outer corky bark, so that in order to destroy the broods of the species of this subdivision the simple removal of the bark is not sufficient; it must be burned or otherwise destroyed. In the species of subdivisions B, C, and D the larvae excavate their mines in the inner layers of bark and also transform to pupae and adults in the inner bark, so that when the bark is removed from the 22 THE SCOLYTID BEETLES.. tree they are exposed to the frost or sun and diying winds, which is sufficient to kill them, without the necessity of burning the bark. It will be seen from the foregoing that the periods in which control operations must be conducted are indicated by the habits and seasonal history of the species involved. In general, the work should be done between the beginning of hibernation in the fall and the beginning of activity in the spring, but in the case of certain species in which there are one or more complete generations within the season of activity, such as species 1,2, and 4, it may be desirable under certain conditions to dispose of the infested trees during the summer, as well as during the winter, especially during the principal development and summer activity of the first generation of larvae. In the case of species 9,10, and 11, the operations may be continued after activity begins in the spring until late in June or the first of July. SECONDARY INJURIES TO THE TREES. Some of the losses resulting from secondary injuries or destruc- tion may be mentioned in this connection. One of these which affects the commercial value of the beetle-killed trees is the bluing of the sap wood. This, according to Dr. Hermann von Schrenk, is due to a fungus which finds its way into the wounds and galleries made by the beetles and rapidly penetrates the sap wood to the heartwood, causing at first bluish streaks and later a uniform bluish-gray appear- ance of the wood. This bluing condition, especially in pine trees infested with species 9 to 11, often prevails long before the leaves of the beetle-infested trees show evidence of decline or death. Other secondary losses consist in abnormal decay of the sapwood and heartwood, but the greatest losses of this class may come from forest fires started in the beetle-killed timber, which may not only complete the destruction of the old dead and the newly infested tim- ber, but also spread into the healthy forests. But there is one redeeming feature in the destruction of the beetle-infested timber by fire, and that is the widespread destruction of the beetles in the infested trees, thus preventing the rapid extension of their ravages which would otherwise occur. FAVORABLE AND UNFAVORABLE CONDITIONS FOR THE BEETLES. It is quite necessary that we should have some general and detailed information in regard to the influences upon the beetles of climate, fires, etc., and how certain methods and practices in the manage- ment of a forest, or in utilizing its resources, contribute to the mul- tiplication of the destructive enemies of the living timber, and how certain other methods may contribute to their reduction or destruc- tion. There is considerable difference in this respect between dif- THE GENUS DENDROCTONUS. 23 ferent sections of the country and between different species of Dendroctonus, as mentioned under the more detailed discussion of the several species. CLIMATIC INFLUENCES. DROUGHT. It is the common impression that the death of pine and spruce timber in certain sections of the Rocky Mountain region is primarily due to a weakened condition resulting from drought and that the work of the insects is secondary. Under the influence of exceptionally severe drought during several successive seasons this may be true to a very limited extent, but our observations lead us to conclude that drought does not offer specially favorable conditions for the multi- plication and destructive work of barkbeetles. In fact, the reverse is more likely to be the rule, since exceptionally dry conditions appear to be more unfavorable for the development of the beetles than humid conditions. The only exception we have noted in which injury is greater in dry sections than humid ones is that of the Douglas fir. In the more southern range of this tree, where the normal dry char- acter of the climate and soil prevails, it suffers more from the Douglas fir beetle (No. 13) than it does in the Northwest, where, under moist conditions and rich soil, the tree reaches its best development. This beetle is very abundant in the Northwest, yet as a rule it confines its attack to the felled and injured timber and rarely attacks the healthy trees. On the other hand, the western yellow pine suffers more severely in the humid sections than it does in the more arid ones, as demonstrated by the work of the Black Hills beetle (No. 10), which is widely distributed over the eastern section of the Rocky Mountain region, yet has been far more aggressive and destructive in the Black Hills National Forest than in the much drier sections in southern Colorado and northern New Mexico and Arizona, and has continued its depredations in the Black Hills unabated through excessively wet as well as excessively dry seasons. The western pine beetle (No. 1) is far more abundant and destruc- tive in the northern and more moist climate of the mountains of Idaho, Oregon, and California than is its near relative, the south- western pine beetle (No. 2) in the drier forested areas of New Mexico and Arizona. The mountain pine beetle (No. 9) is exceedingly destructive to the lodgepole pine at high altitudes and under espe- cially moist conditions. The same may be said of the eastern spruce beetle and the Engelmann spruce beetle. It is evident, therefore, that drought is not an important factor in contributing to the multi- plication or destructiveness of this class of enemies. 24 THE SCOLYTID BEETLES. LOW TEMPERATURE AND SNOW. While the severe cold at the high elevations in which most of the western species prevail appears to have no detrimental effect on the overwintering broods, we have a striking example of its effect on a northern migration of a southern species, in the complete extermina- tion of the southern pine beetle (No. 4) in the Virginias by the excep- tionally cold winter of 1902-3. On the other hand, snows, when sufficiently heavy to break down a large amount of timber, might offer favorable conditions for the multiplication of some of the species like the western pine beetle, the mountain pine beetle, and the Douglas fir beetle. LIGHTNING. In certain sections of the country where a great many pine and spruce trees are struck by lightning during the summer months these trees furnish exceptionally favorable conditions for the perpetuation and multiplication of the pine and spruce beetles. Although the constant supply of such trees furnishes also favorable conditions for the multiplication and perpetuation of the natural enemies of the destructive beetles (insects and birds) , these enemies are frequently not sufficiently numerous to serve as a natural check, and the living timber is attacked by the broods of beetles which develop in the lightning-struck trees. This is especially true in the Southern States, where a pine tree struck by lightning attracts the beetles to the spot, and they not only enter the injured tree but attack and kill a number of those surrounding it. WINDSTORMS. Whenever a windstorm occurring during the period from June to August is sufficiently severe to fell and break a large amount of pine and spruce, favorable conditions may be presented for the multipli- cation of certain of the destructive beetles, provided they are present in the locality in sufficient numbers to infest the felled timber. This has been demonstrated from time to time in Europe, where beetles with much less aggressive habits than the Dendroctonus beetles have, it is said, been thus enabled to multiply to sufficient numbers to attack and kill the living timber and cause serious extension of their depredations into the healthy forest. OTHER INFLUENCES AND CONDITIONS. FOREST FIRES. While some of the species find favorable conditions for their multi- plication in fire-scorched trees, others, like the Black Hills beetle, appear to prefer the uninjured trees. This is due, perhaps, to the fact that if a fire be sufficiently- severe to kill large pine trees,, the bark THE GENUS DENDKOCTONUS. 25 on the lower and middle trunk is so scorched and killed that the beetles can not live in it. Spruce, however, may be killed or weak- ened from injuries to the base and roots by a surface fire, and thus offer especially favorable conditions for the multiplication of the spruce beetles. On the other hand, a forest fire in a forest in which the majority of the trees are infested by broods of beetles and dying from their injuries may contribute to the destruction of the insects and the protection of the remaining living timber. MATURED TIMBER. Practically all of the more destructive species show a decided pref- erence for the larger and best-matured trees, and as a rule these are killed first, and the younger timber is not attacked until later, if at all. This is particularly true of the spruce beetles (Nos. 14 and 15), the southern pine beetle in the East and South, the western pine beetle, and the mountain pine beetle of the West. COMMERCIAL CUTTING. The cutting of living timber for commercial purposes may offer favorable conditions for the multiplication of some of the species, like the Douglas fir beetle and western pine beetle, but if such cut- ting, within a range of less than 50 square miles, is more or less continuous, it appears to serve as a protection to the living timber rather than otherwise. On the other hand, local sporadic cutting may bring about more or less serious results. Some species, like the Black Hills beetle, are evidently not attracted from the living trees by cutting operations, while the southern pine beetle in the Southern States is greatly favored by sporadic cutting, especially if carried on during the summer months. SUMMER CUTTING. The cutting of healthy trees, or even of living beetle-infested trees, during June, July, and August, in a forest or section where the southern pine beetle, the western pine beetle, the mountain pine beetle, or even the Black Hills beetle, is present, is more or less objectionable from the fact that the beetles are attracted by the odor of the exposed bark and wood and often attack many healthy trees in the immediate vicinity of the felled ones. WINTER CUTTING. When any of the more destructive beetles are present in a forest it is important that the principal timber-cutting operations should be carried on during the late fall and winter months, and completed in the spring before the beetles begin to fly. This is especially important when there is a large amount of infested timber to be utilized, because it is necessary to remove the bark from the trunks 26 THE SCOLYTID BEETLES. of such trees or convert them into lumber and burn the slabs before the insects begin to emerge. "Winter cutting of living, healthy tim- ber is much to be preferred when species with a single generation, like the mountain pine beetle, Douglas fir beetle, or the spruce beetles, are present, because dining the following summer the stumps and slash will serve to attract the beetles away from the living trees. And since the broods would remain in the bark during the following: winter they can then be destroyed by burning the slash any time dining the following fall or winter. In the Southeast and in the Rocky Mountain region, however, when species with more than one generation annually are present, it may be necessary to burn the winter slash before the first of July, to destroy the broods of the first generation winch develop from eggs deposited during May or June. NATURAL ENEMIES OF THE BEETLES. Were it not for the natural checks and control of some of the insect enemies of forest trees, the destruction of the forests would evidently be far more continuous and complete, but imder the existmg warfare between the trees and the destructive beetles and between the beetles and their own enemies, a more or less balanced condition in nature is preserved, so that it is only under exceptional conditions that a species of tree or a species of insect is extermi- nated. IXSECTS. The insect enemies of the destructive beetles consist of parasites, predators, and robbers. The parasites are small wasplike insects.0 The adults lay their eggs on, in, or near the beetle larvae, and the minute maggotlike larvae of the parasite, situated either internally or externally, feed on the body fluids and thus cause the death of their victims. W lien the parasite larva reaches its fall development it either changes to a free papa in the mine of its victim or makes a cocoon in which it goes through its transformation. Therefore the presence of certain of the parasitic enemies of the beetle larva? is indicated by the presence of their cocoons in the mines, even after their victims have been destroyed and they themselves have emerged. The principal predators consist of certain adult beetles and their larva?6 (see fig. 32), the adults often feeding on the adults of the destructive beetles before or after they enter the bark, and the larvae feeding on the broods of the beetle larva1 in the bark. There is another class of predatory enemies of the beetles among the true bugs,0 which follow the beetles and larva1 into their galleries a Order Hymenoptera. families Braconida?, Chalcididae, etc. b Order Coleoptera. families Cleridse, Histeridae. Tros:ositidse. Colydiidae, etc. c Family Anthocoridae.j THE GENUS DENDROCTONUS. 27 and mines, and kill their victims by inserting their beaks into their bodies. The so-called robbers (see fig. 30) consist of large bark-boring grubs or larva? of long-horned beetles, a which sometimes rob the barkbeetle larva* of their food supply or kill them outright, by destroying the inner bark before the broods of barkbeetles have completed their development. These, however, do not occur so commonly with the more destructive barkbeetles as with those which, like the bark-boring grubs, are in the bark as the result, and not the cause, of the dying condition of the tree. While some of the Dendroctonus beetles have numerous insect enemies, others have comparatively few. Some of the smaller species, like the southern pine beetle, which often occupy the thin bark on the upper portion of the trunk and branches of the larger trees, and sometimes on young trees, have many parasitic enemies, while others of the small species, as 1, 2, and 5, and the larger species, such as the Black Hills beetle and the Douglas fir beetle, which usually occupy the thick bark, have none at all, or very few. So far as determined, the southern pine beetle has 1 1 parasitic and about an equal number of predatory enemies; the eastern spruce beetle has 5 parasitic and 4 predatory enemies, and the eastern larch beetle 6 parasitic and 2 predatory enemies. Of the western species the mountain pine beetle is the only one on which a parasite has been found, but there are four or five predators common to all, which evi- dently exert quite an important influence in protecting the forests of some sections. With a little assistance on the part of the owner of the forest, this class of beneficial insects will exert a much more power- ful influence in preserving a desirable balance among the contending forces, and thus prevent destructive outbreaks of the beetles. This balanced condition appears to prevail at the present time within the range of the southern pine beetle, and with proper attention to local outbreaks of the beetles it could be maintained. However, this whole subject of parasites and predatory enemies of forest insects and their economic relations is one which has not as yet received the attention it deserves. Mr. Fiske gave the matter considerable attention during his field work in forest insect investigations, but his detail to another branch of the Bureau prevented him from continuing it. BIRDS. Wherever the Dendroctonus beetles have been found in standing timber the work of woodpeckers has been more or less common, and in some trees quite a large percentage of the beetle broods has been destroyed by the birds. The evidence gathered in Maine a few years a Family Cerambycidse. 28 THE SCOLYTID BEETLES. ago indicates quite conclusively that the birds were rendering a most valuable service as a natural check to the multiplication and destruc- tive work of the eastern spruce beetle. The work of birds is common in sections where species 1, 9, and 10 and other western species are prevalent. Yet birds evidently render the greatest service where but few trees are being killed, since their concentrated work may prevent an abnormal increase of the beetles; but where many hundreds or thousands of trees are being killed, the limited number of birds can have little or no effect. Therefore, while the birds are among the foresters' valuable friends, they can not, even with the utmost pro- tection, always be relied upon to protect the forest from its insect enemies. We must remember that there are most complex interre- lations between birds, the injurious insects, the beneficial insects, the enemies of the birds, etc., which do not always result in benefit to the forest. In fact it is often quite the reverse. Therefore, in order for the forester or owner of the forest to derive the greatest benefit from the conflict, he must not onlv direct his efforts toward utilizing as far as possible the natural factors which are contributing to his personal interests, but whenever the enemies of the forest threaten to get beyond natural control he must enter the fight and by radical artificial means force them back to their normal defensive position. DISEASES OF THE INSECTS. While evidence has frequently been found of the work of fungous or bacterial diseases in destroying the adults and immature stages of the beetles, the matter will require detailed study by specialists on such diseases before any definite conclusions can be formed in regard to their economic relations or importance. DISEASES OF THE TREES. Evidence has been found from time to time that the primary cause of the death of isolated large and small trees and saplings was some fungous disease of the roots and base of the stem, and that the larger trees so affected sometimes favored the multiplication of a destructive insect enemy. Evidence has also been found that certain diseases of the inner bark and sapwood, like the bluing fungus studied by Dr. Her- mann von Schrenk,a are sometimes very injurious and destructive to the developing broods of the beetles. It is also apparent that this fungus, which is said to depend largely on the wounds made by the beetles in finding its way into the living bark and sapwood of the standing timber, may also contribute to the more rapid and certain "The "Bluing" and the "Red-Rot" of the "Western Yellow Pine, with Special Reference to the Black Hills Forest Reserve. By Hermann von Schrenk. Bui. 36, Bureau of Plant Industry, 1903. THE GENUS DENDROCTONUS. 29 death of the trees. Therefore this interrelation between plant dis- eases and insects must often be considered in our efforts to locate the primary cause of a trouble. It has been conclusively determined, however, that when the beetles occur in sufficient numbers, they are entirely independent of the aid of other factors or the influence of their enemies, and that they attack and kill perfectly healthy timber over extensive areas. SECONDARY ENEMIES OF THE TREES, AND DEPENDENTS, GUESTS, ETC., OF THE DESTRUCTIVE BEETLES. As soon as the attack of one of the destructive beetles causes a weakened or dying condition of a tree, such a tree becomes at once the breeding place of many other species of barkbeetles and bark and wood boring grubs which can not attack healthy trees. These sec- ondary enemies of a tree are dependent on the more aggressive Den- droctonus beetles or on other factors that may cause a similar weak- ened or dying condition of the trees. Some of them render special service to the destructive beetles by attacking the twigs, the branches, and the unoccupied bark on the upper and lower portions of the trunk, and thus aid in bringing about the certain death of the tree. There are some insects which live in the galleries with the adult beetles, in the relation of guests, others as scavengers, etc., so that it is always important to distinguish which are the real primary enemies, which are secondary, which are beneficial, and which are neutral in their relation to an affected tree. GENERAL METHODS OF CONTROL. While the subject of control is treated under the special discussion of each species, there are some general principles and features which should be mentioned in this connection, especially such as relate to the infestations of standing timber by the broods of the destructive beetles. HABITS AND SEASONAL HISTORY AS SUGGESTING METHODS OF CONTROL. Any systematic plan or method for the destruction and control of these beetles, in order to be least expensive and most successful, must be based on a knowledge of the habits and seasonal history and many other essential features relating to the particular species, or group of allied species, involved in a given problem. The principal facts of importance in this connection are as follows: (a) It is the normal habit of all of the species to infest the bark on the main trunk of the larger to medium sized trees; (b) in all species the devel- oping broods of larvae live in the inner bark; (c) some of the species, as in subdivision A, enter the outer dry bark to transform to adults, 30 . THE SCOLYTID BEETLES. while others, as in subdivisions B, C, and D, transform in the inner bark: ( the inner surface. Later they transform to pupa? and adults in the outer corky bark. Pitch tubes (figs. S, 9) are produced on the main trunk of the living trees attacked. The fading to yellowish and reddish foliage indicates its destructive work. SEASONAL HISTORY. OVERWINTERING STAGES. The broods pass the winter in the outer bark of trees attacked the preceding late summer and fall, as parent adults, young adults in pupal cases, all stages of larvae, and possibly pupae. ACTIVITY OF OVERWINTERED BROOD? The overwintered parent adults extend their galleries or excavate new ones and deposit eggs during April and May, from which broods develop and emerge by the last of July to the middle of August. THE GENUS DENDROCTONUS. 43 The broods of young adults in the pupal cells begin to emerge from the trees about the last of June, and continue to come out until the middle or last of August. The broods of overwintered larvae begin to transform to pupae about the middle of April and to adults toward the last of April, and the latter begin to emerge from the trees about the middle to last of July, so that practically all of them are out by the last of August, although some of the retarded ones continue to emerge until September or later. Fig. 7.— The western pine beetle: Egg galleries. Reduced. (Author's illustration.) FIRST GENERATION. The overwintered broods of adults begin to attack the trees, exca vate galleries, and deposit eggs about the first of July, and continue their activities until September or later. The principal period of attack is during July. The larvae begin to hatch in from four to ten days after the eggs are deposited, and may be found in the bark of the same tree from early in July until October, but the principal development is during July and up to the middle of August. They begin to transform to 44 THE SCOLYTID BEETLES. pupa? about the middle of August, and continue transforming until cold weather, the principal period of transformation being from the middle to the last of August. The pupa? begin to transform to adults after the middle of August, and continue transforming until cold weather, but the principal period of transformation is between the middle of August and the middle of September. The adults begin to emerge from the trees toward the last of August, and continue to come out until in October, or later, but the principal period of flight appears to be from the last of August to the middle "of September. YVhile the majority of the broods of this generation emerge before cold weather, it is evident that some of them overwinter in all stages from larvae to young and parent adults. /lierfiarrA- Fig. 8. — The western pine beetle: Bark showing, a, a. pupal cells: b, exit burrows; c, pitch tubes. Reduced. < From Webb.) larvae, together with some of the parent complete generation annually and a parti SECOXD GEXERATIOX. The records of observa- tions indicate that the ear- lier emerging adults of the first seasonal generation begin to deposit eggs about the last of August, and that the principal period of attack is from the last of August to the middle of September. The larva? be- gin to appear about the first of September, and continue to hatch until in October, or later. Xo evi- dence has been found that the larva3 of this genera- tion transform to pupa3 before winter, but it ap- pears that the broods pass the winter in all stages of adults. Thus, there is one al second one. HABITS. The adults attack the living bark on healthy, felled, and weakened standing western yellow pine and sugar pine. They excavate long, winding galleries (fig. 7) through the inner layers of bark, along the sides of which single eggs are deposited at intervals of one-half inch or more. The larva1 normally do nut exeavate their mines through the inner layers of bark, but through the middle or outer portion of the inner bark. When the larvse have fully developed, they bore THE GENUS DENDROCTONUS. 45 out into the outer corky bark to pupate and transform to adults. After the adults are fully matured, and the proper time has come for them to emerge, they bore out of the bark (fig. 8) and fly to other trees, there to start a new at- tack. While very few observa- tions have been made on the habits of flight, it is probable that the beetles swarm during the evening and at night. ECONOMIC FEATURES. While it appears that this species prefers to attack weak- ened and felled trees, or isolat- ed healthy ones, it often attacks large numbers of healthy trees and causes extensive depreda- tions. It is especially destruc- tive to the western yellow pine (see fig. 10) in central Idaho, and in the mountains and higher valleys of eastern Wash- ington, Oregon, and California. It must therefore be classed among the important primary enemies of the pines within its range. As a rule, the largest and best trees are attacked, and the winding egg galleries beneath the bark serve to com- pletely girdle them and cause their death before the broods have developed and emerged. EVIDENCES OF ATTACK. The external evidence of at- tack by this species on healthy trees is the presence of pitch tubes (figs. 8, 9) at the entrance of the galleries, or reddish bor- ings lodged in the flakes of bark on the trunk and around its base. Trees attacked in Fig. 9, -Work of the western pine beetle: Pitch tubes on bark of tree. (From Webb.) 46 THE SCOLYTID BEETLES. July will usually have the foliage fading or turning yellow in August; those attacked in August may have the foliage fading in September and October, while those attacked in September may fade during the late fall or winter or remain green until the following spring. All, however, will have yellow to reddish foliage before the broods have entirely emerged the following July. As a rule, all of the broods will have emerged from the trees found at any season with reddish to brown and falling foliage. The exceptions are when only part of a tree or the bark on one side of the trunk is killed by the first attack, and the remaining living bark is infested later in the same season or during the next. Positive evidence that the above conditions are caused by this species must be based on authentic identification of specimens found in the bark of trees so affected. EFFECTS ON COMMERCIAL VALUE OF THE WOOD. The commercial value of the wood of trees killed by this beetle is reduced by the bluing of the sapwood, often before the leaves begin to turn yellow, but the heartwood, especially of the larger trees, does not deteriorate until decay sets in several years after the tree's death. The loss, therefore, is not necessarily very great where the timber is felled and utilized immediately after a destructive attack, but if the insect-killed trees are left standing until the branches and tops break off and fall (fig. 10), the loss is often serious or complete. Serious losses of a secondary nature, both of the dead and adjoining living timber, may often result from forest fires started in the dead timber. Therefore the losses, first from the ravages of this species and second by fire, have been severe in some localities. FAVORABLE AND UNFAVORABLE CONDITIONS FOR THE BEETLE. Favorable conditions for the multiplication and destructive work of this beetle are found in areas of large, matured timber, and espe- cially where such trees are frequently struck by lightning or injured or felled by storms, etc. The unfavorable conditions for attack upon the living timber are found in areas of vigorous, recently matured, or young growth, and where timber-cutting operations are continued from year to year under modern systems of forest management. METHODS OF CONTROL. In localities and areas of greater or less extent where it is known that scattering clumps of trees are dying from the attack of this species, the principal clumps of infested trees should be located in September to March, and the infested bark on the main trunk and larger branches removed and burned, or the logs converted into lum- ber and the slabs burned. This work should be begun not earlier THE GENUS DENDROCTONUS. 47 than October and should be completed by the first of June. If at least 75 per cent of the infested trees are thus treated, sufficient numbers of the broods will be destroyed the first year to protect the remaining timber for several years. Then, if all patches of infested timber are subsequently located and barked before the broods emerge, it should serve to keep this enemy under complete control. Fig. 10.— Western yellow pine killed by the western pine beetle, Yosemite National Park. (Original.) Summer operations in the barking of infested trees are not to be recommended, except in special cases where it is desirable to destroy the broods of the first generation. In this case the work should be done during the period of principal larval development — that is, from the middle of July to the middle of August, or when the leaves of the infested trees are just beginning to fade. 48 THE SCOLYTID BEETLES. It has been determined that this species can be attracted to girdled and felled trap trees. Under certain conditions, therefore — as in the case of the absence of logging operations and where only a few scat- tering trees are infested — it may be desirable, as a means of main- taining control, to provide a few trap trees to attract the first genera- tion. This can be done by girdling two or three inferior trees to the heartwood or by felling them in June. Then, if they become infested with this beetle, the bark should be removed from the main trunk and burned by the middle of August. Trap trees to attract the second generation should be prepared in August and September and barked before the first of the following May. Usually an aver- age of one to three trees to the acre should be sufficient for this purpose. However, the number will depend largely upon the preva- lence of the insect. (See preceding reference to trap trees, pp. 33-34.) Fig. 11.— The western pine beetle: Distribution map. (Author's illustration.) Continued timber-cutting operations within an area of from 20 to 50 square miles usually provide sufficient breeding places in the bark of the logs and tops of the felled trees to satisfy the requirements of this species; but if the living timber should be at any time threat- ened by the broods emerging from the slash, or if it is desirable to include in timber-sale and timber-cutting regulations certain provi- sions for the burning of the slash, this work should be done about the first of August for the slash of the winter and spring cutting, and dur- ing the winter for that of the late summer and fall cutting: the latter period, however, is preferable, on account of the danger of starting forest fires bv summer burnins:. THE GENUS DENDROCTONUS. 49 BASIS OF INFORMATION. The preceding information on the western pine beetle is based on investigations by the writer at McCloud, Cal., at Grants Pass, Oreg., near Spokane, Wash., and at Moscow, Idaho, April and June, 1899, and in the Yosemite National Park and Yosemite Valley, California, June, 1904; by Mr. J. L. Webb, at Moscow and Troy, Idaho, Septem- ber and October, 1900, and at Centerville, Stites, Kooskia, Grimes, Placerville, and Smiths Ferry, Idaho, April to September, 1905; by Mr. H. E. Burke, at Smiths Ferry, Idaho, October, 1904, in the Yosem- ite National Park, at Wawona, and in the Yosemite Valley, Califor- nia, June to August, 1906, and at Joseph, Oreg., in 1907, and by Mr. V. S. Barber, at Sterling and Chester, Cal., in 1908. Additional localities through correspondence and from other collections are Badger, Ballard, and the Santa Barbara Na- tional Forest, Cal. ; Winthrop and Auburn, Wash.; Pokegama, Oreg., and Missoula, Mont. The species is represented in the forest-insect collection of the Bureau of Entomology by sev- eral hundred specimens. BIBLIOGRAPHY. Hopkins, 1899a, p. 395; Hopkins, 18996, pp. 13, 20, 26; Hopkins, 19016, pp. 66, 67; Hopkins, 1902c, p. 21; Hopkins, 1904, p. 18; Webb, 1906, pp. 17-30; Hopkins, 1907, pp. 162-163; Hopkins, 1909, pp. 81-85. No. 2. THE SOUTHWESTERN PINE BEETLE. (Dendroctonus barberi Hopk. Figs. 12-14.) Fig. 12.— The southwest- ern pine beetle {Den- droctonus barberi): Adult. Greatly enlarg- ed. (Author's illustra- tion.) The southwestern pine beetle is a small, rather stout, light to dark brown barkbeetle, from 2.5 to 4.7 mm. in length, with a broad grooved head, sides of the pro- thorax slightly narrow toward the head, elytra with moderately coarse rugosities, and elytra and declivity without long hairs. (See fig. 12.) It attacks healthy, injured, and felled western yellow pine in southern Colorado and Utah and in the mountains of Arizona, New Mexico, western Texas, and northern Mexico. The adults excavate winding, transverse, egg galleries (fig. 13) through the inner bark and mark the surface of the wood. The lar- val mines are rarely visible on the inner surface of the bark, but extend through the middle portion and into the outer corky portion, where the larvae transform to pupae and adults. The presence of this species in standing timber is indicated by pitch tubes on the trunk similar to those made by the western pine beetle (figs. 8, 9) and by the fading yellowish to red foliage. 89535— Bull. 83, pt. 1—09 5 50 THE SCOLYTID BEETLES. SEASONAL HISTORY. OVERWINTERING STAGES. The broods pass the winter in aU stages from young to matured larvae, young adults, parent adults, and possibly pupae, in the outer bark of trees and logs attacked by the parent beetles the previous summer. ACTIVITY OF OVERWINTERED BROODS. The overwintered parent adults begin to excavate galleries and deposit eggs as soon as warm weather permits in the spring, and con- tinue to do so until about the first of June. The overwintered broods of young adults begin to emerge toward the last of May (northern area) and continue to come out until the last of June or later. The overwintered larvae begin to transform to pupae and adults soon Fig. 13.— The southwestern pine beetle: Egg galleries. (Author's illustration.) after activity begins in April or May, but retarded individuals may ib >t develop until in July, or later. The adults from the overwin- tered larvae begin to emerge toward the last of May, and continue emergence through June or until the latter part of July, or later. Probably all are out by the first to middle of August. FIRST GENERATION. The overwintered broods of adults begin to deposit eggs about the first of June and continue doing so until August, or later, but the principal period of attack is during June and July. The larva? begin to hatch early in June, and begin to transform to pupa? and adults early in July, the principal transformations being in July. The broods of adults begin to emerge about the middle of July, the prin- cipal period of emergence being in the latter part of July, but they THE GENUS DENDROCTONUS. 51 continue to come out until September, or later. Mr. Webb's observa- tions on the development of the broods from the time eggs were deposited on June 4 and June 9 to the beginning of emergence on July 22 and July 29, show a period from deposition of eggs to emer- gence of adults of about fifty days. The principal period of flight of the adults of this generation appears to be during the latter part of July and first of August, but it is evi- dent that while some of the more retarded broods may hibernate as matured adults and larvae, nearly all develop and emerge before activity ceases in the fall. SECOND GENERATION. The records of observations indicate that the earlier emerged adults of the first generation attack the trees and begin to deposit eggs about the first of August, the principal attack being in August and September. The larvae begin to hatch early in August and begin transforming to pupae about the 1st of September, but no adults of this generation have been observed during the first season. The winter is passed in all stages of larvae, with some of the parent adults. Therefore, there is one complete seasonal generation and a partial development of a second, or two complete generations annually. The principal differ- ences in the seasonal history and generations of species 1 and 2 are the earlier beginning and ending of the first period of attack by the overwintered broods of No. 2, and the more complete development of the second generation. The habits of the two species are quite similar, except that the present species is usually associated with one or more others — Nos. 3, 5, 8, and 10. ECONOMIC FEATURES AND METHODS OF CONTROL. The economic features and methods of control relating to this species are quite similar to those of the western pine beetle. In case it should become isolated from the other species of Dendroctonus with which it is usually associated and become independently destructive, and if summer barking of the infested trees should be found desirable, the work should begin (under average conditions) about the middle of June and end at the middle of July, or just a month earlier than for the western pine beetle. The same rule applies for trap-trees for the first generation, which should be prepared in May and barked by the middle of July. The fall and winter work of barking trees may begin a little later, but should be completed by the 1st of May. In the more southern range of this barkbeetle the beginning and completion of such control work should be two months earlier than at the same altitude in its more northern range. (See " Methods of control" under western pine beetle, pp. 46-48.) 52 THE SCOLYTID BEETLES. BASIS OF INFORMATION. Information on this species is based on investigations by the writer at Williams, Ariz., September, 1902, at Vermejo, N. Mex., May, 1903, and near Flagstaff, Ariz., May, 1905; by Mr. J. L. Webb at Flagstaff, Williams, and Dead Mans Flat and near the Grand Canyon, Ariz., May to September, 1904, in the Lincoln National Forest at Cloudcroft, and in the Capitan Mountains, New Mexico, and in the Santa Cata- lina National Forest, Arizona, May to September, 1907, by Mr. W. F. Fiske at Meeks, Capitan, and Cloudcroft, N. Mex., and in the Davis Mountains, Texas, in 1907; by Mr. H. E. Burke at Panguitch Lake, Utah, in 1907; by Mr. W. D. Edmonston at Monte Vista, Colo., in 1907. Additional localities through correspondence are Show Low, Chiricahua Mountains, Arizona; San Bernardino, Cal.; Fort Garland, Fig. 1-4. — The southwestern pine beetle: Distribution map. (Author's illustration.1) Colo.; Escalante, LTtah, and Santa Fe, X. Mex. The species is repre- sented in the forest-insect collection of the Bureau of Entomology by more than 300 specimens of the insect and its work. This species is closely related to the western pine beetle, but is dis- tinguished by the slightly more slender form, coarser rugosities, aud distinct])' impressed striae of the elytra. It is easily distinguished from the other species occupying the same range by the denser rugosi- ties and absence of lonii" hairs on the elytra. BIBLIOGRAPHY. Hopkins, 1904 (under " The Arizona Dendroctonus"), pp. 42, -14; Hopkins, L909, pp. 85-87. THE GENUS DENDROCTONUS. 53 No. 3. THE ROUNDHEADED PINE BEETLE. (Dendroctonus convexifrons Hopk. Figs. 15-17.) The roundheaded pine beetle is a somewhat elongate cylindrical, reddish-brown to black, rather shining barkbeetle, 4 to 6 mm. in length, with the front of the head convex, and without frontal groove, the prothorax broad, only slightly narrowed toward the head, and finely punctured, the elytra with coarse rugosities toward the base, and the declivity with fine punctures and long erect hairs. (See fig' 15.) It attacks injured, felled, and healthy western yellow pine from southern Arizona to northern New Mexico and southern Colorado. It excavates long, slightly winding, longitudi- nal, and sometimes transverse and branched egg galleries (fig. 16) extending through the inner living and dying bark and grooving the surface of the wood. At intervals along the sides of the galleries single eggs are deposited. The short, cylindrical, grub- like larvae extend their larval mines at right angles to the egg galleries, usually through the inner layers of bark, and mark the sur- face of the wood. The transformation to pupge and adults is sometimes in the inner bark, but probably more often in the outer bark. This barkbeetle is nearly always as- sociated with one or more of four other species of Dendroctonus — Nos. 2, 3, 5, 8, and 10. The presence of this species is Fio.is.-The roundheaded pine indicated by pitch tubes on the trunk and beetle (Dendroctonus convexi- , ,, j. v i i t i j. v frons): Adult. Greatly enlarg- by the fading and reddish foliage. ed. (Author's illustration.) SEASONAL HISTORY. OVERWINTERING STAGES. The winter is passed in the bark of trees attacked the preceding summer, as parent adults, young to matured larvae, young adults, and possibly pupae, the parent adults in the egg galleries, and the broods in the outer and inner bark. ACTIVITY OP OVERWINTERED BROODS. The overwintered parent adults extend the old galleries or excavate new ones from the time activity begins in May until the last of June, or later. The overwintered broods of young adults begin to emerge, probably, in June, and continue to come out until September. The overwintered larvae begin to transform to pupae and adults in June and apparently continue to develop and transform to adults until activity ceases in the fall. Some of the adults which have transformed 54 THE SCOLYTID BEETLES. from overwintered larvae may 'emerge during the period from August to October, but apparently the majority go over the second winter, together with a few larva3. Full-grown larva? observed by Mr. Webb on June 28 had not all transformed to adults on October 10, and only a few adults had emerged. The broods developing from the eggs deposited by the overwintered parent adults may develop to adults Fig. 16. — The roundheaded pine beetle: Egg galleries and larval mines. Reduce'! Author's illustration. before activity ceases in the fall, but the majority evidently pass the winter as medium to matured larvae. GENERATION. The overwintered broods of young adults begin to emerge and deposit eggs in June and continue to do so until September, or later. Some of the larvae from these eggs may transform to pupa? THE GENUS DENDROCTONUS. 55 and adults before cold weather, but evidently no adults emerge before winter. It is very evident that there is only one partial generation annually, and that some individuals may not complete their development until' the second year. It is evident, also, that the most retarded adults of the first generation may live over and deposit eggs the third year. HABITS. So far as known, this species confines its attacks to the western yellow pine, but it is probable that it will attack other species of pine growing within its range. It is nearly always associated with the other species of Dendroctonus and other barkbeetles in injured, dying, and felled trees. The adults enter the living to dying bark on the main trunk of the trees and excavate long, slightly winding, longitudinal, oblique, or nearly transverse and sometimes branched galleries through the inner bark, and often groove the outer layer of wood. In contrast with other species of Dendroctonus which are usually associated with it, except the Black Hills beetle, the larval mines are usually, but not always, exposed in the inner bark, and often mark the surface of the wood. Some of the larvae may trans- form to adults in the inner bark, but as a rule they enter the outer corky bark for this purpose. The young adults remain there until time for them to emerge and fly. Nothing is known of the food and flight habits, and many other facts are obscure, owing to the confusion of this with other species before it was recognized as distinct. ECONOMIC FEATURES. The fact that this species is usually associated with one or more of species 2, 3, 5, 8, and 10 renders its specific relation to the death of trees doubtful. It is evident, however, that if it should become iso- lated from the other species and occur in large numbers, it would be fully capable of killing trees on its own account. During the past year it was found associated with the Black Hills beetle in the destruc- tion of a large amount of timber, with evidence that some of the trees were killed by it alone. METHODS OF CONTROL. Whenever it is found that this species is causing the death of timber or is associated with other species in doing so, the bark should be removed from the main trunk of the infested trees and burned. The work should be done between the first of October and the middle of the following June. (See also "General methods of control," pp. 29-35.) 56 THE SCOLYTID BEETLES. BASIS OF INFORMATION. The preceding information relating to this barkbeetle is based on investigations by the writer at Williams, Ariz., September, 1902, at Vermejo, N. Mex., May, 1903, at Flagstaff, Ariz., May, 1904, and near Ft. Garland, Colo., June, 1906; by Mr. J. L.Webb at Flagstaff, Ariz., May to September, 1904, at Cloudcroft, N. Mex., and in the Santa Catalina National Forest, Arizona, May to September, 1907; by Mr. W. F. Fiske, at Meeks, Cloudcroft, and Capitan, N. Mex., in 1907; by Mr. H. E. Burke, at Panguitch, Utah, in 1907; by Mr. W. D. Edmonston, at Monte Vista and Laveta,, Colo., and La Sal, Utah, in 1907. Additional localities through correspondence are Las Animas County, Colo.; Show Low, and Paradise, Ariz., and Fig. 17.— The roundheaded pine beetle: Distribution map. (Author's illustration. the Fort Wingate Military Reservation, New Mexico. The species is represented in the forest-insect collection of the Bureau of Ento- mology by more than 100 specimens of the insect and of its work. BIBLIOGRAPHY. Hopkins, 1909, pp. 87-90. No. 4. THE SOUTHERN PINE BEETLE. (Dendroctonus frontalis Zimm. Figs. 18-31.) The southern pine beetle is a slender, cylindrical, brownish to black beetle, 2.2 to 4.2 mm. in length; the head is broad, with median ele- vations each side of a distinct frontal groove; the pro thorax is punc- THE GENUS DENDROCTONUS. 57 tured and but slightly narrowed toward the head; the elytra have moderately coarse rugosities between indistinct rows of punctures, and the declivity is convex, with a few long hairs. (See fig. 18.) It attacks healthy, injured, and felled trees of all of the pines and spruces, from southern Pennsylvania southward into Florida and westward into eastern Texas and Arkansas. It excavates long, winding egg galleries (fig. 19) through the inner bark, and marks, but does not groove, the surface of the wood (fig. 24). The whitish, legless larvae excavate short, broad larval mines at more or less regular intervals at right angles along the sides of the egg galleries, usually, but not always, exposed in the inner bark. The transformation to pupae and adults takes place in the outer corky bark. The presence of this species is indicated by pitch tubes on the main trunk of living trees, and by the fading and yellowish to red foliage as the trees die from its attack. It is a very destructive enemy of southern and southeastern pines. SEASONAL HISTORY. Northern Section. overwintering stages. The broods pass the winter in the outer bark of trees attacked during the preceding summer and fall, as parent adults, matured larvae, and possibly pupae, and as small larvae in the inner bark, but principally as matured larvae in the outer bark. ACTIVITY OF OVERWINTERED BROODS. North of South Carolina the overwintered par- Fig . 18.— The southern pine beetle (Dendroc- tonus frontalis): Adult. ent adults begin to extend their galleries or ?AreIU,y *n\ar+ged; ° & (Author's illustration.) excavate new ones as soon as warm weather permits in the. spring (March to May) and continue their activities probably until toward the middle of May or later. The overwin- tered broods of young adults begin to emerge about the first of May. The first swarming period occurs about the middle of May, but strag- glers continue to come out probably as late as the middle of June or July. This relates especially to its northern range and to the higher altitudes. The overwintered broods of matured larvae begin to trans- form to pupae and adults in March and April, but the principal trans- formation is in April, so that the adults are ready to emerge with the overwintered broods of young adults. Some of the broods of over- wintered young larvae probably develop in time to emerge with the swarm, but some of them are generally retarded and do not com- plete their development until in July, or possibly as late as August. It is evident that the majority of the overwintered broods are out by 58 THE SCOLYTID BEETLES. the middle of June and that all are out by the last of July. Broods from eggs deposited by overwintered parent adults probably develop and emerge by the first or middle of June. FIRST GENERATION The overwintered young adults deposit their first eggs early in May, and the excavating of galleries and oviposition continue prob- ably into June, especially if the parent adults leave the completed galleries to excavate others, which they evidently do, though the general and principal attack by the overwintered broods is from the Fit,. 19.— The southern pine beetle. Egg galleries and larval rnine>: a, Entrance; 6, entrance burrow: c. egg gallery; d, normal larval mine; e, abnormal larval mine; /, terminal; g, ventilating bur- rows. Slightly reduced. (Authors illustration.) middle to the last of May. The larva? begin to hatch early in May and continue their active development during June, the more retarded individuals continuing active into August. They begin to trans- form to pupa? and adults about the middle of June, and continue until the retarded individuals are all transformed, in August or later. The developed broods begin to emerge toward the last of June and continue to come out during July or until all of the retarded broods and individuals are out in August and September or later: but practically all of the normally developed broods of the first generation are out by the last of July. THE GENUS DENDROCTONUS. 59 SECOND GENERATION. The first eggs of the second generation are deposited by adults of the first generation during the first week of July. The principal attack, however, is during the latter part of July and first of August. The larvae of this generation begin to hatch about the middle of July, continue to hatch during the latter part of July and early part of August, begin transforming to pupae and adults during the first half of August, and continue to do so into September or later. The broods of adults begin to emerge about the 10th of August and con- tinue to come out during the middle to last of the month, and until the last of the retarded broods have left the trees, in September or later; but practically all of the normally developed broods are evidently out by the middle of September. THIRD GENERATION, The adults of the second generation evidently begin to attack the trees and deposit eggs for the third generation about the middle of August, and continue to do so into September or later, though the principal attack is during the last half of August. The larvae begin to hatch in a few days after the eggs are deposited, and develop principally during the last of August and first half of September, but some of them do not complete their development before hiber- nation begins in the fall. The matured larvae transform to pupae and adults principally during September, but continue their trans- formations into November or later. The developed broods begin to emerge about the middle of September, and probably continue to come out until November or later. The majority, however, evidently emerge before the middle of October. FOURTH GENERATION. The adults of the third generation evidently begin to attack the trees and deposit eggs about the middle of September, and continue to do so during the latter part of September and first of October, until cold weather. The principal development of the larvae is dur- ing October, practically all becoming full grown before hibernation begins, so that the majority pass the winter as full-grown larvae in the outer bark. Some of the earliest broods evidently begin transform- ing to pupae and adults toward the middle of October, and some of them may emerge in October and November, but evidently by far the larger number of both the young adults and the developed larvae pass the winter in the outer bark. 60 THE SCOLYTID BEETLES. FIFTH GENERATION. There may be a partial or beginning of a fifth generation, especially at the lower elevations and more southern localities of the northern section, the individuals of which pass the winter as parent adults and young larvae. It is evident that in the northern section of the range of this spe- cies there are from two to three complete seasonal generations dur- ing the period from about the first of May until activity ceases in the fall, or at any rate all of the broods of at least two generations develop and emerge during the period of activity within the range including the higher elevations of North Carolina and lower eleva- tions at the northern limit, and that all of the broods of at least three generations develop and emerge at the medium and lower ele- vations south of Virginia, represented by a central locality included in a range of, say, 1,000 feet above and 500 feet below Try on, N. C, while portions of the fourth and all of the fifth generation overwinter. PERIODS OF DESTRUCTIVE ATTACK. In the area including the mountains of North Carolina and north- ward there is one principal period of destructive attack, viz, during August and September, and in the area represented by Tryon, N. C, there are two principal periods of destructive attack, one from the middle of July to the last of August, the other during September and October. Southern Section. In the southern section, including the Atlantic or Gulf region of loblolly and longleaf pines, there is a complex overlapping of prob- ably five or six generations, most difficult to define on account of the almost continuous activity during the year, but of course more or less retarded during the colder weather of the winter months. It would appear, however, that the principal periods of destructive attack are similar to those of the Tryon section. HABITS. The adult beetles enter the living bark, usually on the upper por- tion of the main trunk of standing healthy or injured trees or on the entire trunk of newly felled ones, and excavate long, sublongitudinal, winding egg galleries (figs. 19-22) through the inner bark. Eggs are placed in little niches along the sides of these galleries at more or less regular intervals of one-half inch or more. The freshly hatched larvas, which are short, stout, whitish grubs with a faint frontal elevation in the middle of the head and with the opposite end of the body blunt or truncate, excavate their larval mines at right angles to the egg gallery (fig. 19), and usually exposed THE GENUS DENDROCTONUS. 61 in the inner bark. The normal larval mine is first short and thread- like, then suddenly enlarges into a broad cavity, but sometimes, when the bark dies too rapidly or is otherwise unfavorable, a thread- like abnormal larval mine is extended for a much greater distance. When the larvae are fully matured they bore out into the corky outer bark and excavate individual cells (fig. 22) in which those of the summer brood transform to pupae and adults and those of the fall broods pass the winter before going through their transformations the following spring. After the adults are fully matured and when ji Fig. 20.— The south- ern pine beetle : Termination of egg galleries. (Author's illustration.) jfclyjS1 ill? Fig. 21.— The southern pine beetle. Beginning of egg galleries: a, In living bark; 6, in dying bark; c, marked on surface of wood (white area represents normal .ap- pearance of wood preserved by resin.) (Author's illustra- tion.) Fig. 22.— The southern pine beetle. Bark showing: a, Pitch tubes; b, entrance burrow; c, egg gallery; d, ventilating burrow; e, pupal cells; /, exit burrows; g, inner bark; /;, outer bark. (Author's illustration.) the proper time comes for them to emerge, they bore out through the bark and fly away. The flight or swarming of this species evidently occurs late in the evening and at night, and consequently very few observations have been made on the flight habits. The finding of the beetles in electric- light globes and otherwise attracted to light is conclusive evidence that the beetles fly at night, and the fact that groups of trees are simultaneously attacked by great numbers of the beetles indicates a swarming: habit. An especially interesting feature in the congre- 62 THE SCOLYTID BEETLES. gating habit of the beetles was observed by Mr. W. F. Fiske, who found great numbers congregated under the loose flakes of bark of healthy trees just before their simultaneous entrance into the living inner bark. Another peculiar habit of the beetles is that of migrat- ing from one locality or group of trees where the broods developed to another locality or group of trees some distance away, instead of continuing their attack on the trees immediately surrounding those Fig. 23.— The southern pine beetle: Old egg galleries in living tree, with surrounding callus of new wood. (Author's illustration.) Fig. 24.— The southern pine beetle. Egg gallery in living tree marked on surface of wood six years before block Avas cut from tree: a, Mark of gallery on original surface; b, resinous wood; e, surface scar six years later; d, original surface or 7-year-old annual layer of wood; e, <\x subsequent annual layers of wood formed over original wound. Author's illustration.) from which they emerge. Apparently there are rare exceptions to this rule. While this species will breed in injured and felled trees, it shows a decided prefer- ence for those living and healthy, whenever it occurs in sufficient numbers to attack and kill them. Its broods of larva? must have living, or at least partially living, bark in which to complete their rapid normal development. It attacks the bark on the middle or upper trunk of medium to large pine and spruce trees, and usually selects the largest and best trees first. After the larger trees are killed the middle to lower trunk of the smaller trees may be attacked. The habit of attack and methods of excavating gal- leries are similar to those of the smaller western and Mexican spe- THE GENUS DENDROCTONUS. 63 cies, all of which extend their galleries from the entrance in a trans- verse or sublongitudinal and tortuous course through the inner bark (fig. 19). Those of different pairs of beetles frequently cross each other so that the many primary galleries, independent of the larval mines, serve to com- pletely girdle the tree and kill the bark. Thus these winding galleries cause a much more rapid death of the bark and foliage than do the straight longitudinal gal- leries, like those of the spruce beetles and the Black Hills beetle. The trees are killed by the girdling effect of the winding primary galler- ies in the bark of the middle portion of the trunk, which, it has been demonstrated, is the most vital part, or at least has less power of resisting injuries than the lower portion and base. Instead of the leaves of the trees re- maining green until the next season, as they do on trees infested by the spruce beetle and the Black Hills beetle, all except those on the trees attacked late in the sea- son Commence to fade Fig. 25.— White pine timber killed by southern pine beetle in a few weeks after the %?£££2Z$!££Z "^ " * ™ "* trees become infested. ECONOMIC FEATURES. This species may be considered as one of the most dangerous enemies of the pine forests of the Southern States. It devastated the pine forests over large areas in West Virginia and Virginia in 1891 and 1892, and the extensive dying of pine timber in the Southern States during 64 THE SCOLYTID BEETLES. the past century , to which there are numerous references, was more than likely caused by it. It has been more or less active in the States south of Virginia, southward to Texas, since 1902, and in some localities and during some years it has killed a large amount of timber. It is therefore a constant menace to the pine timber of the Southern States. EVIDENCES OP ATTACK. The first external evidence that living trees are being attacked by this species is the presence of pitch tubes (fig. 22) on the upper to middle trunk, or of reddish boring dust lodged in the loose bark and around the base of the trees. If the attack is sufficient to kill the trees, the presence of the in- sect will be indicat- ed in about two weeks by the fading and yellowish ap- pearance of the leaves, and in about a month after the attack the leaves will be yellowish to reddish, all of the bark except that on the base of the trunks will be dead, and the broods of the destructive ene- my will be ready to emerge or will have emerged. After the leaves have become reddish brown practically all of the broods will be out. Positive evidence, however, that the above-described external conditions are caused by this beetle is obtained only by authentic identification of specimens of the insect or its work taken from the affected trees. The presence of the insect in destructive and dangerous numbers is indicated by frequent patches of djdng pine or spruce during Juty, August, and September, and the sudden death of the timber over large areas will indicate a destructive invasion requiring prompt and radical measures for its control. Fig. 26.— Table Mountain pine, Mineral County, W. Va., seven years after it was killed by tbe southern pine beetle. (Original, from photograph.) THE GENUS DENDEOCTONUS. 65 EFFECTS ON COMMERCIAL VALUE OF THE WOOD. The commercial value of the wood of trees killed by this beetle is reduced by the bluing of the sap wood (fig. 29), often before the leaves begin to turn yellow, though the heartwood, especially of the larger spruce and yellow pine, usually remains sound for many years after the trees die; both the sap and heart wood of the smaller trees, and even of the large pitch, loblolly, and Table Mountain pine, deteriorate rapidly (figs. 26, 27), and therefore must be utilized SSff^T immediately after the Jg* . ^T trees begin to die, in order to save anything of com- mercial value. Serious losses of a sec- ondary nature, both of dead and adjoining living timber, may result from fires started in the dead timber. Therefore the prompt utilization of the beetle-infested trees and the prevention of forest fires are important to ob- viate total destruction of the timber. FAVORABLE AND UNFAVOR- ABLE CONDITIONS FOR THE BEETLE. Favorable conditions for the multiplication and spread of the beetle are found in areas of large, matured timber and where the trees are fre- quently struck by light- ning, felled, or injured by storms, etc., during the summer months. g^^te^^^SgL^tt^ Fig. 27.— A forest of Table Mountain pine, Mineral County, W. Va., seven years after it was killed by the southern pine beetle. (Original, from photograph.) The odor from the exposed wood, and perhaps from the wilting foliage of a few trees cut in the midst of a healthy growth of pine dur- ing the summer, serves to attract this species, apparently from a long distance, and to induce attack on the surrounding healthy trees. Therefore, any irregular or sporadic local cutting of timber for fuel or any limited purpose during the summer months furnishes most 89535— Bull. 83, pt. 1—09 6 66 THE SCOLYTID BEETLES. favorable conditions for the concentration of individuals from widely scattered colonies and broods, and thus increases their power of attack- ing and killing the surrounding living trees. By this means their forces are greatly augmented, and much of the surrounding timber is killed. If conditions favorable for the continued concentration of the beetles prevail from year to year, an invasion like that of 1891 and Fig. 28.— Spruce timber killed by the southern pine beetle, mountains of Transyl- vania County, N. C (Original.) 1892 may be started, which may far exceed any forest fire hi the history of the country, both in the extent of area covered and in the number of trees of commercial value killed. Unfavorable conditions for the multiplication of the insect and its destructive attacl on living timber will be found in large areas where the older matured trees have been removed and where continued timber-cutting operations are carried on under some regular system of THE GENUS DENDROCTONUS. 67 forest management, as also where there are regulations governing the time of year when the timber shall be cut. in both regular and irregu- lar operations, as well as the time when lightning-struck and other- wise injured trees shall be removed or barked. METHODS OF CONTROL. In order effectually to destroy the insect, it is only necessary to remove the infested bark from the trunks and burn it. It is entirely unnecessary to burn or otherwise destroy any part of the wood from which the bark has been removed, because the destructive beetle does not enter the wood and rarely breeds in the bark of the tops and branches. With this particular species, however, it is necessary to burn the bark after or before it is removed, because the ma- tured larvae, pupae, and adults pass the winter in the outer dry bark, where they would otherwise survive and emerge in the spring, to attack other trees. In localities or areas of greater or less extent where it has been positively determined that the timber is attacked and killed by this beetle, the principal groups of trees which are actually in- fested with the broods should be located in the period from November to March, and the standing trees, including all of the larger ones, so infested should have the bark removed from the main trunks or be felled and barked, or the entire trunk scorched, burned, placed in water, or converted into lumber and the slabs burned, as in each case is more practicable or advisable. In the northern section this work should be begun not earlier than the 1st Fig. 29.— The southern pine beetle: Section of pine trunk, bark removed, showing the galleries marked on surface of wood and the dark patches caused by the blue- ing fungus. (Original.) 68 THE SCOLYTID BEETLES. of November and completed not later than the 1st of April, and in the southern section it should be begun in December and completed in February. If at least 75 per cent of the infested trees, including all of Fig. 30.— Egg galleries and larval mines of the southern pine beetle, and larval mines of ronndheaded bark-borer. (Original.) those in the larger patches, within 10 or 15 square miles are thus treated, it should destroy enough of the broods to protect the remain- ing timber for several years. If, then, this practice is followed up THE GENUS DENDROCTONUS. 69 whenever small patches of infested timber are found it should serve to keep this enemy under complete control. Summer operations in the felling and barking of infested trees are not to be recommended except in special cases, when, for example, it is desirable under a clear-cutting system to include the healthy timber with the infested, or when practically all of the timber over a large area is infested during the spring and summer; otherwise, if only the infested trees are cut and healthy ones left, the felled and barked trees attract the flying beetles to the locality, and thus the death of a large amount of the surrounding healthy timber results. If it is desirable to make clear cuttings during the summer, to include small or large areas of infested timber, it should be done during the principal periods of larval development — August and September in the northern section, and from July to October in the southern section. Whenever it is desirable to protect a small or large estate, or a particularly valuable section of the forest surrounded by forested areas in which the infested timber can not or will not be cut and barked, the greatest precautions should be taken to prevent the cutting of pine timber for any purpose during the spring, summer, and early fall. The only exception would be lightning-struck or storm-broken and felled trees, which, under certain conditions, should be cut and removed, or burned with the tops, if possible, the next day after the injury occurs. If the logs are removed the tops should be burned over the stumps.. If pine cord wood is cut during the summer, it should be done under the clear-cutting system and confined to a section of the forest away from the more valuable timber which it is desirable to protect from insect attack. Cord wood, new lumber, etc., should never be piled in proximity to living pine trees, neither should building operations involving the use of new pine lumber or fresh paint be conducted during the summer in or near a desirable grove of pineor spruce. All of the above relates especially to sections where the beetle is present in the surrounding forest. Some experiments conducted by Mr. W. F. Fiske, while working on forest insects, indicate that if the infested trees are felled in November and December and left flat on the ground and the upper side of the trunk is scored or blazed so as to facilitate the entrance of water from rains and melting snows, the broods will be killed by the abnormal wet condition of the inner bark. When the infested timber is near streams or ponds the broods may be destroyed by placing the unbarked trunks or logs in the water, pro- vided the work is done before the broods begin to emerge. 70 THE SCOLYTID BEETLES. Whenever the infested timber can be utilized for lumber the burning of the bark and slabs is all that is necessary. BASIS OF INFORMATION. Information on this species is based on investigations by the writer for the West Virginia Agricultural Experiment Station in many localities in West Virginia, Jul}', 1891, to December, 1896: for the United States Department of Agriculture at Fletchers, X. C, July and November, 1902; at Tryon, N. C, July, 1902, March, 1903, and July, 1904; at Boardman, X. C, Inman, X. C, and Kirbyville, Tex., Fig. 31.— The southern pine beetle: Distribution map. (Author's illustration.) Xovember, 1902; at Pink Beds and Pisgah Ridge, X. C, July, 1904; at Virginia Beach, Va., Xovember and December, 1907, and April, May, and June, 1908; by W. F. Fiske at Tryon, X. C, March to September and December, 1903, April to December, 1904, March to December, 1905, and May, June, and July, 1906; at Clyo, Ga., August, 1903; at Pisgah Ridge, X. C, September, 1903, and September, 1904; at Corne- lia, Ga., Xovember, 1903; at Chicora, S. C, Xovember, 1904; at Call, Tex., February and Xovember, 1905; at Beaumont and Dewey- ville, Tex., Thomasville, Ga., Montgomery, Ala., Wilson and Singer, La., and Pink Beds, X. C, March, 1905; at Ducktown and Wetmore, Tenn., Ellijay, Ga., October, 1905, and Green Bay, Va., June, 1906. Additional localities through correspondence and from other collections are Calhoun, Ala.; Green Bay, Cobbs Island, Glen Allen, and Auburn Mills, Va.; Hampton, Ark.; Demorest, Ga. ; Indian Territory, and Haw Creek, Fla. The species is represented in the forest-insect col- THE GENUS DENDROCTONUS. 71 a Fig. 32.— The European barkbeetle-destroyer (Clerus formicarius) , introduced from Europe in 1892- 1893: a A, Adult, dorsal aspect, natural size at right; B, adult, showing attitude when feeding on barkbeetle; C, pupa and details; D, larva and details. Greatly enlarged. (Author's illustration.) a Hopkins, 1899a, pp. 297-231. 72 THE SCOLYTID BEETLES. lection of the Bureau of Entomology by 65 specimens in the West Virginia Agricultural Experiment Station collection and by more than 150 in the general Bureau of Entomology collection. BIBLIOGRAPHY. Hopkins, 1892a, pp. 64-65; Hopkins, 18926, p. 353; Schaufuss, 1892, p. 316; Hopkins, 1893a, pp. 187-189; Hopkins, 18936, p. 143; Hopkins, 1893c, pp. 186, 213; Hopkins, 1893a7, pp. 123-129; Hopkins, 1894, p. 292; Hopkins, 1894a, pp. 71-76; Hopkins, 1894c, p. 348; Lintner, 1895, p. 500; Hopkins, 1896, pp. 246, 250; Hopkins, 1897a, pp. 29-41; Hopkins, 18976, pp. 35-36; Hopkins, 1897c, pp. 79, 94-95, 147-151; Chittenden, 1897, pp. 67-75; Hopkins, 18986, pp. 104-105; Schwarz, 1898, pp. 81-82; Hopkins, 1899a. pp. 394-414, 448; Hopkins, 18996, pp. 11, 13, 14; Chittenden, 1899, pp. 55-56; Hopkins, 19026, p. 21; Hopkins, 1902c, p. 20; Hopkins, 1903a, p. 59; Hopkins, 19036, pp. 270-275. 281; Hopkins, 1904, pp. 41, 42, 44; Felt, 1905, p. 6; Hopkins. 1906c, p. 80; Webb, 1906, pp. 20-22; Hopkins, 1907, p. 163; Hopkins, 1909, pp. 90-95. Xo. 5. THE ARIZONA PINE BEETLE. (Dendroctonus aiizonicus Hopk. Figs. 33, 34.) The Arizona pine beetle (fig. 33) is a somewhat elongate, brown to black beetle, from 4 to o mm. long, with broad grooved head, sides of prothorax but slightly narrowed toward the head, finely to rather coarsely punctured, and elytra with slightly coarse rugosities toward the base and declivity, the latter with a few long hairs. (Seefig.34.) It attacks healthy, injured, and felled western yellow pine in central Arizona, and evidently excavates galleries similar to those of the southwestern pine beetle, with which it is usually confused. The larva? make concealed food burrows in the inner bark, and transform to pupa? and adults in individual cells in the outer bark. Like the other species, its destructive work would be indicated by pitch tubes on the trunk and by the fading yellowish to reddish foliage. Fig. 33. — The Arizona pine beetle (Dendroc- tonus arizonicxis): Adult. Greatly en- larged. (Author's il- lustration. ) SEASONAL HISTORY. This species was not recognized as distinct from the southwestern pine beetle until after the principal field observations had been made, and while many specimens were collected they were nearly always associated with the latter in similar galleries: therefore there is somewhat meager evidence on which to base conclusions relating to seasonal history, habits, etc. Apparently, however, its habits are in most respects similar to those of the southwestern pine beetle. THE GENUS DENDROCTONUS. 73 although it is distinctly separated by specific characters. It is more nearly related to the southern and smaller Mexican pine beetles than to any other species, and therefore it may be found that it has two generations, and a partial third, annually. It is also probable that under isolation and favorable conditions it may, like the southern pine beetle, become very destructive. (See " Economic features" and " Methods of control" under Nos. 1, 2, and 4.) BASIS OF INFORMATION. Data regarding this species were obtained through investigations by the writer at Williams, Ariz., September, 1902, and Flagstaff, Ariz., May, 1904, and by J. L. Webb at Flagstaff and Williams, Ariz., 7T---i .:••.• ;>v..:**-- J.-.-,:-'-'- 1 Fig. 34.— The Arizona pine beetle: Distribution map. (Author's illustration. ) May to September, 1904, and Flagstaff, Ariz., August, 1907. It is represented in the forest-insect collection of the Bureau of Entomology by over 50 specimens. This species can be easily distinguished from No. 2, with which it agrees in size, by the long hairs on the declivity of the elytra, and from the smaller examples of No. 8 by the fine punctures of the striae of the declivity, from No. 3 by the grooved head, and from No. 6, to which it is closely allied, by the distinctly more pubescent pronotum and elytra. BIBLIOGRAPHY. Hopkins, 1909, pp. 95-97. 74 THE SCOLYTID BEETLES. Xo. 6. THE SMALLER MEXICAN PIXE BEETLE. (Dendroctonus mexicanus Hopk. Figs. 35, 36. ) The smaller Mexican pine beetle (fig. 35) is a dark brown, elongate, cylindrical barkbeetle, ranging in length from 3 to 4 mm., with head broad and grooved, prothorax but slightly narrowed toward the head, and punctured, and elytra with coarse rugosities toward the base and declivity. the latter with long hairs. It attacks pine trees in Mexico, where a large amount of timber has died in certain localities, evi- dently owing to the work of this and the larger Mexican pine bee- tle. It excavates winding egg galleries (fig. 35) through the in- ner bark, the larval mines being concealed, like those of the west- ern and southwestern pine bee- tles, beneath the inner surface of the bark. Very little appears to be known of the seasonal his- tory and habits of this species, Fig. 35.— The smaller Mexican pine beetle (Den- droctonus mexicanus): Adult, greatly enlarged, and section of egg gallery, slightly enlarged. (Author's illustrations.) Fig. 36.— The smaller Mexican pine beetle: Distribution map. (Author's illustration.) but evidently they will be quite similar to those of the southwestern, southern, and Arizona pine beetles. It will therefore be subject to the same general treatment for its control, namely, the removal and THE GENUS DENDEOCTONUS. 75 burning of the infested bark during the principal period of larval development and during the inactive or overwintering periods, if such are found within its range. This species has not been recognized within the United States, but it is not improbable that it may be found in the pine forests of south- ern Arizona and New Mexico. The writer has identified thirty-six specimens received from Prof. A. L. Herrera and Dr. S. J. Bonansea, collected from pine in Ame- cameca, Michoacan, and Tacubaya, Mexico. BIBLIOGRAPHY. Hopkins, 1906c, p. 80; Hopkins, 1909, pp. 97-99. No. 7. THE LARGER MEXICAN PINE BEETLE. (Dendroctonus parallelocottis Chap. Figs. 37-39.) The larger Mexican pine beetle is a somewhat elongate, cylin- drical, dark brown to black barkbeetle, 5 to 6 mm. in length, with broad, deeply grooved head; broad prothorax, with sides nearly parallel and but slightly narrowed toward the head, and elytra with dense, moderately coarse rugosities, the declivity with coarse punc- tures and long erect hairs. (See fig. 37.) It attacks living pine trees in Mexico, excavating coarse, slightly winding, longitudinal or oblique and sometimes branched egg galleries (fig. 38) through the inner bark. The larval mines are evidently concealed beneath the inner layers of bark, and the larvse evidently transform to pupae in separate cells in the outer bark. It is usually associated with the smaller Mexican pine beetle in the same tree. Very little appears to be known in regard to the seasonal history of this species, but it is so closely related to the Colorado pine beetle in general characters that it is probably quite similar in seasonal history as well as in habits and in the character of injury to the trees, except in such minor differences as may be brought about by its more southern range. It is evident that the unhealthy and dying condition of the pine in certain localities in Mexico, which has been reported from time to time, is caused largely by this species and by the smaller Mexican pine beetle. Ten specimens of the beetle and one of the galleries, received from Prof. A. L. Herrera, collected in Michoacan, etc., have been examined and identified by the writer. If this species is found overlapping the range of the Colorado pine beetle, it can be distinguished from that species by the slightly longer prothorax, with sides more parallel and less narrowed toward the head. BIBLIOGRAPHY. Hopkins, 1906, pp. 80-81; Hopkins, 1909, pp. 99-101. 76 THE SCOLYTID BEETLES. Fig. 37.— The larger Mexican pine beetle (Dendroctonus parallelocollis) : Adult. Greatly enlarged. (Author's ill.) Fig. 38.— The larger Mexican pine beetle: Sec- tion of egg gallery. Reduced. (Author's ill.) Fig. 39.— The larger Mexican pine beetle: Distribution map. (Author's illustration.) THE GENUS DENDROCTONUS. 77 No. 8. THE COLORADO PINE BEETLE. (Dendroctonus approximates Dietz. Figs. 40-43.) The Colorado pine beetle (fig. 40) is a somewhat elongate, cylin- drical, dark brown to black barkbeetle, 4 to 7.4 mm. in length, with broad, deeply grooved head; prothorax broad, punctured, and but slightly narrowed toward the head, and elytra with dense, mod- erately coarse rugosities, the declivity with coarse punctures and long, nearly black, erect hairs. It attacks injured, dying, and healthy west- ern yellow pine, from central Colorado and Utah to southern Arizona and New Mexico. It excavates long, slightly winding, longitudinal and sometimes transverse, and branched egg galleries through the inner living and dying bark, and grooves the surface of the wood (fig. 41); the larval mines are usually concealed beneath the inner bark and the larvae usually transform to pupae and adults in the outer bark. It is nearly always associated with one or more of species, 2, 3, 5, and 10 in the same tree. SEASONAL HISTORY. OVERWINTERING STAGES. The winter is passed as parent adults, young adults, young to matured larvae, and possibly pupae — the parent adults in the egg galleries in the inner bark and the broods in the outer bark of trees attacked the preceding summer. ACTIVITY OP OVERWINTERED BROODS. From the beginning of warm weather until in June the over- wintered parent adults extend their old galleries and excavate new ones and deposit eggs. The overwintered broods of young adults begin to emerge from the trees early in June and continue to come out until September or later. The overwintered broods of larvae probably begin their transformation to pupae and adults in June and continue to do so until September or later. The adults begin to emerge in June, but their principal period of emergence is in July, and they continue to come out until September or later. It is probable that some individuals or broods which pass the winter as young larvae may be retarded in their development and pass the second winter as matured larvae or adults. GENERATION. The overwintered broods of young adults evidently begin to attack the trees, excavate galleries, and deposit eggs early in June, or earlier in their southern distribution. The principal attack is in June, July, and August, but they continue the attack until Septem- ber or later. Some of the broods from eggs deposited in June may develop to adults in September, but it appears that they do not emerge and that the majority of the broods of this generation pass the winter as larvae, young adults, and parent adults. 78 THE SCOLYTID BEETLES. There is, therefore, but one generation annually, and it is probable that, like the roundheaded pine beetle, some individuals of the same generation may not complete their development until the second year, and that some adults may live over and deposit eggs the third 3'ear. HABITS. The habits of this species appear to be similar to those of the round- headed pine beetle, with which it is frequently associated in the same tree. The character of the primary or egg gallery is distinguished by the larger, coarser appearance and by the Fig. 40.— The Colorado pine beetle {Den- droctonus approximate) : Adult. Greatly enlarged. (Author's illustration.) absence of exposed larval mines on the in- ner surface of the bark. The character of the primary galleries is shown in figures 41 and 42. It appears that while some of the larvae may transform to adults in the inner bark, the majority of them transform in separate cells in the outer bark. The flight and food habits of the adults are evidently similar to those of the other species. ECONOMIC FEATURES. This species has been found attacking perfectly healthy trees in sufficient numbers to kill them. Therefore, if it should become isolated, and under favorable conditions multiply rapidly, it might easily become very destructive. As a rule, however, it prefers to Fig. 41.— The Colorado pine beetle: Single egg gallery. Reduced. (Author's illustration.) THE GENUS DENDROCTONUS. 79 breed in injured, dying, and felled trees, in company with one or more of the other species. (See also general discussion under " Char- acter and Extent of Depredations" and " General Methods of Con- trol" (pp. 4 and 29-35), and "Economic Features/' etc., for Nos. 1, 2, and 4. BASIS OF INFORMA- TION. Information re- garding this bark- beetle is based on investigations by the writer at Williams, Ariz., September, 1902, at Flagstaff, Ariz., in 1904, and at Palmer Lake, Colo., October, 1905; by Mr. J. L. Webb at Flagstaff, Ariz., May to September, 1904, in the Capi tan Moun- tains, and White Mountains, and at Cloudcroft, N. Mex., and in the Santa Catalina National Forest, Rincon Mountains, and Chir- icahua National For- est, Arizona, May to September, 1907 ; by Mr. W. F. Fiske at Capitan, Cloudcroft, andMeeks, N. Mex., March to May, 1907; by Mr. H. E. Burke at Kamas, Pan- guitch, and Pan- guitch Lake, Utah, Fig. 42.— The Colorado pine beetle: Egg galleries (Author's illustration.) Reduced. July, 1907; by Mr. W. D. Edmonston at Brookvale, Monte Vista, and Laveta, Colo., in 1907. Additional localities through correspondence and from other collections are the Chiricahua Mountains, New Mexico ; Paradise and Show Low, Ariz., and Glenhaven, Colo. It is repre- 80 THE SCOLYTID BEETLES. sented in the forest-insect collection of the Bureau of Entomology by more than 150 specimens. This species is closely allied to No. 7, of Mexico, and was at one time thought by the writer to be a variety of it,a but recent studies indi- cate that it is a good species, distinguished by the more shining pro- notum, more distinctly narrowed and faintly constricted toward the head, the hairs on the sides toward the base slender and less numer- ous. Therefore it is thought best to retain it as a good species. It is easily distinguished from the other species associated with it in the same region by its elongate form, larger size, and by the deep frontal groove of the head and stiff, erect, blackish hairs on the declivity. Fig. 43.— The Colorado pine beetle: Distribution map. (Author's illustration.) BIBLIOGRAPHY. Schwarz, 1902, p. 32; Hopkins, 1903a, p. 61; Hopkins, 1904, p. 44; Hopkins. 1905, p. 11; Hopkins, 1906c, p. 81; Hopkins, 1909, pp. 101-104. No. 9. THE MOUNTAIN PINE BEETLE. (Dendroctonus monticolae Hopk. Figs. 44-50.) The mountain pine beetle is a stout, black, cylindrical barkbeetle 3.7 to 6.4 mm. long, having the head broad, without frontal groove, but with a short longitudinal impression above the middle; the prothorax short, broad, and punctured, with sides narrowed and slightly con- stricted toward the head; the elytra with moderately coarse rugosi- ties between rows of punctures, the latter usually indistinct on the sides; the declivity slightly impressed each side of the suture, and aProc. Ent. Soc. Wash., VII, p. SI. THE GENUS DENDROCTONUS. 81 with a few long hairs, the striae narrow, and the spaces between quite broad and roughened with sparsely placed granules. (See fig. 44.) It attacks injured, felled, and healthy silver or western white pine, western yellow pine, and lodgepole pine, in Montana, western Wyo- ming, Idaho, Oregon, and Washington; it also attacks sugar pine, western yellow pine, and lodgepole pine in the mountains of Washing- ton, Oregon, and California. It excavates very long, nearly straight to slightly, and sometimes strongly, winding egg galleries through the inner living bark and grooves the surface of the wood (figs. 45, 46). The eggs are placed in approximate groups at short intervals along the sides, and the short and broad to long and slender larval mines are exposed in the inner bark; the larvae transform to pupae and adults in separate cells, exposed or concealed in the inner bark. This WM^'^^m Kl species is sometimes associated with the western pine beetle in the same tree, but usually it works independently and oc- cupies the greater part of the bark on the main trunks. Infested trees are first in- dicated by pitch tubes and later by the fading yellow to reddish foliage. SEASONAL HISTORY. OVERWINTERING STAGES. The winter is passed as larvae, young adults, and parent adults, in the inner bark of trees attacked the preceding sum- mer and fall, the parent adults in the egg galleries or ventilating burrows, and the broods in the larval mines or pupal cells. Fig. 44.— The mountain pine beetle (Dendroctonus monticolx): Adult. Greatly enlarged. (Author's illus- tration.) ACTIVITY OF OVERWINTERED BROODS. As soon as the weather is favorable in April and May the overwin- tered parent adults extend their incompleted egg galleries or excavate new ones in the remaining living bark on the dying trees and deposit eggs. The overwintered broods of young adults begin to emerge in July. The principal period of emergence is in August, but the retarded broods continue to come out until September, or later. The broods of larvae begin to transform to pupae and adults in April and May and continue to do so until September, or later. Some of the larvae evidently pass the second winter as matured larvae and adults. The broods from eggs deposited by the overwintered parent adults evidently develop to adults in July and August. 89535— Bull. 83, pt. 1—09 7 82 THE SCOLYTID BEETLES. GENERATION. The overwintered broods of adults begin to attack the trees, exca- vate galleries, and deposit eggs about the first of August and continue to do so during August and September, until October or later, but the principal period of attack is in August. The larvae begin to hatch early in August and begin to transform to pupa? and adults in Septem- ber and October. Under favorable conditions a few adults may emerge late in the fall, but evidently it is the normal habit for the Fig. 45.— The mountain pine beetle: Egg galleries and larval mines in bark. (Author's illustration.) Reduced. broods of this generation to pass the winter as all stages of larvae, as adults in pupal cases, and as parent adults, and it is evident that some individuals of the delayed broods do not complete their development until in the fall of the year following and that some of them pass the second winter as parent and young adults. There is, therefore, but one generation annually, with a possible overlapping of the generations of three years during the summer. THE GENUS DENDROCTONTJS. 83 HABITS. This species apparently prefers to attack injured and felled trees, but is often found attacking healthy living ones. It infests at least Fig. 46.— The mountain pine beetle: Egg galleries and larval mines grooved in surface of wood. (Author's illustration.) four species of pine and one species of spruce, and will doubtless be found in other species of pine and spruce growing within its range. The parent adults excavate their long, nearly straight, or winding, longitudinal galleries through the living inner bark, and groove the 84 THE SCOLYTID BEETLES. surface of the wood of the main trunk. The larvae excavate short and broad, or long and slender food burrows at right angles to the primary gallery, and usually transform in their individual pupal cells exposed in the inner bark or between the inner bark and wood, the cells marking the surface of the wood. After the new broods of adults become matured, thev often bore out the bark intervening > %J © between the cells and congregate under the loose bark before they begin to emerge: some of them, however, bore directly out from the transformation cells. Scarcely anything is known of the flight habits, but this species evidently flies in swarms late in the evening or at night. It is not improbable, however, that, like its near relative, the Black Hills beetle, it may at times swarm during the day. ECONOMIC FEATURES. While this species apparently prefers to attack injured and felled trees, it is in some localities often found attacking and killing the living timber over considerable areas. As a rule, the largest and best trees are attacked first, and their egg galleries and larval mines com- pletely girdle the trunks from near the ground up to the middle branches. The silver pine or western white pine (fig. 47) and lodgepole pine in Idaho and Montana, the sugar pine (figs. 48, 49) in Oregon and California, and especially the lodgepole pine in the Yosemite National Park, and in northwestern Oregon have suffered severely from its ravages. EVIDENCES OF ATTACK. The first external evidence of attack on living timber is the pres- ence of' pitch tubes on the outer bark of the trunk or of reddish bor- ings lodged in the flaky bark and around the base of the trees with normal green foliage. The second important external evidence of attack, and of infested trees, is the fading of the foliage in the fall and spring, followed by a yellowish or sorrel-top condition in May to June, and by red-tops during the period from July to September. The internal evidence is found by cutting into the bark and revealing the characteristic gal- leries occupied by the broods, but positive evidence of attack or infestation by this species is determined only by authentic identi- fication of specimens taken from the bark. Trees attacked for the first time early in August may have the foliage fading late in the fall. but as a rule the foliage remains green until the following spring. The broods begin to emerge by the time the leaves begin to change to the red-top condition, and are all out by the time all of the leaves are dead and red. Exceptions to this rule are frequently found, THE GENUS DENDROCTONUS. 85 where only the top or one side of a tree was killed the first year, or when living bark remains toward the base, which is attacked the second year by the overwintered parent adults and young adults from the overwintered broods. But it is safe to conclude that after the leaves are all dead and brown, very few representatives of the broods will be found in the bark. Fig. 47.— Silver or western white pine killed by the mountain pine beetle in the Priest River National Forest, Idaho. (Original.) EFFECTS ON COMMERCIAL VALUE OF THE WOOD. The commercial value of the silver pine, sugar pine, and lodgepole pine, owing to the thin sapwood, is often not seriously impaired for many years after the trees die, provided they are not injured by fire, storms, wood-boring grubs, and premature decay. The yellow pine, with its thick sapwood, suffers immediate deterioration owing to the bluing fungus which follows the attack of the beetles, causing the 86 THE SCOLYTID BEETLES. wood to blue long before the leaves begin to fade. Except for the secondary injuries by wood-boring insects, fire, etc., the keartwood of the larger trees will remain sound and valuable for several years. While, however, there may not be a very great loss from leaving the dead timber standing until the heartwood begins to deteriorate, the danger of destruction by forest fires is so great that, in order to insure Fig. 48.— Two giant sugar-pine trees killed by the mountain pine beetle, and one dying from recent attack, Yosemite National Park, Cal. Note horse and man by dying tree, indicating diameter of tree at base. Approximate diameter, 8 feet. (Original.) against complete loss, the attacked and infested timber should be felled and utilized before the broods of the beetle develop and emerge, or within two or three years. FAVORABLE AND UNFAVORABLE CONDITIONS FOR THE BEETLE. Favorable conditions for the multiplication and destructive work of this insect are found in so-called primitive forests with a predomi- nance of mature timber, and where trees are frequently struck by THE GENUS DENDROCTONUS. 87 lightning, broken, or felled by storms, landslides, etc., or injured by fire. Unfavorable conditions for attacks on living timber will be found in areas of vigorous young to matured growth under some system of forest management which provides for the utilization of the old timber and especially that injured by storm, lightning, fire, etc. Fig. 49.— The mountain pine beetle: Tops of the trees shown in figure 48. (Original.) METHODS OF CONTROL. Whenever it is positively determined that this species is killing the timber and that the bark of living or dying trees contains living broods, the principal groups of infested trees should be located and marked during September, and then during the period beginning in October and ending in the following July the infested bark should be removed from the main trunk. The simple removal of the bark, 88 THE SCOLYTID BEETLES. without burning, is sufficient to kill the broods of this species. If large numbers of lightning-struck trees, and those injured by storms or otherwise, become infested during the summer, they should be barked before the succeeding July. The felling and barking of newly- attacked trees during August and September is not to be recommended for this species. This species, unlike D. ponderosse, is attracted to injured and felled trees, and therefore may be trapped to a limited extent in trees felled during July and August, and may be destroyed by removing the bark any time between October and the following July. Tins may or may not provide sufficient breeding places in the felled trees and stumps to prevent attacks on living timber. Whenever it is necessary or desirable to destroy the broods of this insect in the logs, stumps, and tops, the timber sales or timber- cutting regulations relating to living timber should require that if the slash from winter, spring, .and summer cutting is to be burned it should be done during the succeeding fall, winter or spring, and that the work be completed before the first of the succeeding July. Sum- mer burning, to destroy the broods of this species, is undesirable and entirely unnecessary if it can be done later. The regulations relating to infested timber should require that the first work be directed either to removing the infested bark from the main trunks of the standing trees or to felling and barking the trees, or to utilizing the timber and burning the slabs, so that this essential part of the work may be completed within the specified time, after which the logging operations, including the disposal of the barked and old dead timber, or of the living timber, if the last is included in the sale, may be prosecuted until it is time to begin the barking operations the following October, on any new infestation which may appear within the area covered by the sales. The lodgepole pine, with its very thin bark, offers more favorable conditions for combating this enemy than the thick-barked western yellow pine and sugar pine. While the parent adults may attack the thinner bark on the upper portion of the trunk and on smaller trees, it is only in the thicker bark on the lower portion of the trunk of the medium to larger trees that the broods will reach their best development. Therefore, while many trees may be killed by the beetles, the removal of the infested bark from the lower portion of the trunks of a comparatively few of them may be all that is nec- essary, and since this bark can be removed from the standing timber the work need not be expensive. In fact, it may be desirable and more practical to give the infested trees to anyone who will bark them within the specified time. Whenever the infested timber is m the vicinity of streams or lakes the insects may be destroyed by placing the unbarked logs in the THE GENUS DENDROCTONUS. 89 water. Scorching the bark or burning the timber outright, or utiliz- ing it and burning the slabs, may answer the same purpose. It is quite evident that if the infested lodgepole pine be cut in the period from September to February, and the trunks, logs, or trees with infested bark on them crib-piled in the open, the bark will dry sufficiently to kill the broods before they can develop and emerge. Hacking or scoring the bark on the upper side of the logs or felled trunks of the silver pine or sugar pine during December, to let the water in, would doubtless kill the majority of the broods before the time for them to emerge. These suggestions relating to methods of treating unbarked timber should be tried by the foresters and lumbermen and the practical results reported, as should all practical results from the adoption of our recommendations. Failures, as well as successes, should be reported. Fig. 50.— The mountain pine beetle: Distribution map. (Author's illustration.) BASIS OF INFORMATION. Information concerning this species is based on studies by the writer at Grants Pass, Oregon, and Sand Point and Kootenai, Idaho, in 1899; at Priest River, Idaho, in 1902, and in the Yosemite National Park and Yosemite Valley, California, June, 1904; by Mr. J. L. Webb, at Moscow, Idaho, in 1900; at Centerville, Smith's Ferry, and Collins, and in Boise County, Idaho, June to September, 1905; by Mr. H. E. Burke, at Smith's Ferry, Idaho, October, 1904; at Longmires Springs, Wash., September, 1905; at Wawona, Summerdale, Little Yosemite, Yosemite, Lake Tenaya, Tioga Road, and Soda Springs, Cal., May to September, 1906, and at Joseph, Oregon, and in the Wallowa National Forest, August, 1907. Additional localities, from other 90 THE SCOLYTID BEETLES, collections and through correspondence , are Piedmont and Keystone, Wyo.; Pokegama, Ashland, and Washington National Forest (Port- land), Oregon; Columbia Falls, Lewis and Clarke National Forest, Saltese, Missoula, Medicine Bow National Forest, Lolo National Forest (Iron Mountain) , and Big Four, Mont. : Coeur d'Alene National Forest and Weiser National Forest, Idaho. It is represented in the forest-insect collection of the Bureau of Entomology by more than 500 specimens, including all stages and work. BIBLIOGRAPHY. Hopkins, 18996 (under Dendroctonus n. sp.), pp. 15, 26; Hopkins, 19016, p. 67; Hopkins, 1902c, p. 21; Hopkins, 1903a, pp. 59-60; Hopkins, 1904 (under ''mountain pine Dendroctonus"), pp. 19, 42, 45; Hopkins, 1905, p. 1; Uebb,1906,p. 22; Hopkins, 1909, pp. 105-109. Xo. 10. THE BLACK HILLS BEETLE. (Dendroctonus ponderosse Hopk. Figs. 51-59.) The Black Hills beetle is a stout, black, cylindrical barkbeetle, 4 to 7 mm. in length, with head broad and without frontal groove, but with slight longitudinal impression above or behind the middle; the prothorax short, broad, and punctured, the sides narrowed and slightly constricted toward the head; the elytra with moderately coarse rugosities between the rows of punctures, which are usually distinct on the sides, and the declivity, which bears a few long hairs, slightly impressed each side of the middle line, the impressed striae narrow, and the interspaces broad and roughened with sparsely placed, coarse granules. (See fig. 51.) The adult beetles attack living and sometimes injured and felled, yellow pine, lodgepole pine, limber pine, Mexican white pine, white spruce, and Engelmann spruce from the Black Hills, South Dakota, to southern Arizona, and westward into Utah, and are very destructive. The parent beetles excavate long, nearly straight, longitudinal egg galleries (fig. 52) through the inner living bark and groove the surface of the wood on the main trunk (figs. 53, 54). The eggs are placed at quite regular intervals, or more often arranged in groups of four or five along the sides. The short, broad larval mines and trans- formation cells are exposed in the inner bark and mark the surface of the wood; the short, whitish, grublike larvae (fig. 51) transform to pupae (fig. 51), usually exposed in the inner bark, and the broods usually work independently of other species and occupy exclusively the greater part of the bark on the main trunks of the trees. The attack causes pitch tubes (figs. 55, 56) on the trunk of the infested trees in the summer and fall, and the leaves fade and turn yellow and red the following season during the period from May to August. THE GENUS DENDROCTONUS. 91 SEASONAL HISTORY. OVERWINTERING STAGES. The winter is passed in the inner bark on trees attacked the preceding summer and fall, as parent adults in the egg galleries, all stages of larvae in the larval mines and transformation cells, and as broods of young adults in transformation cells; but principally as larvae. ACTIVITY OF OVERWINTERED BROODS. As soon as warm weather begins in April and May the over- wintered parent adults extend their incompleted egg galleries and Fig. 51. — The Black Hills beetle {Dcndroctonus ponderosx): a, Adult; 6, larva; c, pupa, a, Greatly enlarged; b, c, less enlarged. (Author's illustrations.) excavate new ones in the remaining living bark on the dying trees and deposit eggs. The overwintered broods of young adults begin to emerge from the trees by the middle of July, but the main swarm does not appear until the last of July and first of August. Some of the retarded broods continue to come out until October, or later. The broods of larvae begin to transform to pupae and adults about the middle of May, and continue to do so during the period from June until September, or later, and begin to emerge in August. 92 THE SCOLYTID BEETLES. The broods from eggs deposited by the overwintered parent adults may develop to adults in August and September, but evidently remain in the bark until the next season of activitv. Fig. 52.— The Black Hills beetle: Egg galleries and larval mines. Slightly reduced. < Author' illustration.) GENERATION*. The overwintered broods of young adults begin to attack the trees, excavate galleries, and deposit eggs toward the last of July; the principal attack is during August, but continues during Sep- tember and until October, or possibly later. The eggs hatch and the larvae begin to feed about the first of August. The principal THE GENUS DENDROCTONUS. 93 activity of the larvae is during the latter part of August, but they continue active until the beginning of hibernation in the fall. The larvae of a few of the most advanced broods may begin to transform to pupae and adults toward the last of September and in October, but by far the greater number overwinters in different stages of larvae with the parent adults. There is, therefore, but one generation each year. It is evident, however, that some re- tarded individuals from the preceding generation may pass the second win- ter as young and parent adults. Thus, during the early summer there may be an overlapping of representatives of two and even three annual generations. HABITS. This species appar- ently prefers to attack living timber, but will breed to a very limited extent in injured and felled trees. It infests at least four species of pine and two species of spruce, and will doubt- less attack other pines and spruces (except the "Douglas spruce") growing within its range. It prefers the western yellow pine, or bull pine. Ine largest and best Fig. 53.— The Black Hills beetle: Tree with bark removed, show- trees are USUallv at- in& eg£ galleries grooved and marked on surface of wood. , , n , . (Author's illustration.) tacked tirst, but- arter these are killed it will attack and kill the medium to small trees and even saplings 8 or 10 feet high or only a few inches in diameter. The parent adults excavate their long, nearly straight, longi- tudinal egg galleries in great numbers through the inner bark, where they often closely parallel each other. The larvae excavate short and broad or long food burrows at right or oblique angles to the egg galleries through the intervening bark, and transform to pupae 94 THE SCOLYTID BEETLES. and adults in individual cells at the farther end or toward the middle of their larval mines, which are exposed in the inner bark when it is removed from the tree. Both the egg galleries and larval mines cause marks and grooves on the surface of the wood. After the new broods of adults become matured, they burrow through the intervening bark between their cells, and congregate in the general Iff JKBlK • >■ ** ■L^^lwP- fp^-ffiB UlflJH^n^w i IP Fig. 54.— The Black Hills beetle: Galleries in bark and marked on scoring chip. About one-third natural size. (Author's illustration.) cavity thus formed, until the proper time for them to emerge, when they all come out and fly in swarms to attack the remaining living timber. Sufficient information relating to the flight of this species has been secured to indicate quite conclusively that it flies in swarms during the day, and probably at night. THE GENUS DENDROCTONUS. 95 ECONOMIC FEATURES. This species apparently differs from all of the others in its decided preference for living timber, in which it excavates its egg galleries in such a manner as to kill the tree and make the conditions favorable for the development of its broods. It is, therefore, a primary enemy of the first importance, especially as related to the western yel- low pine in the eastern sec- tion of the Rocky Moun- tain region south of east- ern Montana. It has de- stroyed a vast amount of the best timber in the Black Hills National Forest of South Dakota, and is threatening the destruction of practically all of the best timber there, as well as much of the reproduction. It is also destructive to the pine in Colorado, New Mexico, and Arizona. There is evi- dence that extensive forests have been destroyed in Col- orado by this beetle and by resulting forest fires during the past fifty or seventy- five years. EVIDENCES OF ATTACK. The first evidence of at- tack and infestation on liv- ing timber is the appear- ance of pitch tubes on the bark of the main trunk, or, in the absence of these, of reddish borings lodged in the loose bark and on the ground around the base of the trees. This is usually the only ex- ternal evidence from the time the trees are attacked in the summer and fall until the following spring. Sometimes during the winter, and especially in the period from April to June, the more noticeable evi- Fig. 55.— The Black Hills beetle: a, Pitch tubes on sur- face of bark, reduced; b, same, two-thirds natural size. (Author's illustration.) 96 THE SCOLYTID BEETLES. 1 i i Ik HP • ... « Br'- US Fig. 56.— Work of the Black Hills beetle in the Black Hills National Forest: 4, Small freshly at- tacked fine tree, showing pitch tubes. B, Marks of primary galleries on surface of wood when bark is removed. C, Freshly attacked tree, showing pitch tubes; near tree not attacked. D, Dead tree, showing where outer 1 ar'c lias been removed by woodpeckers. (Author's illus- tration.) THE GENUS DENDROCTONUS. 97 dence is found in the fading foliage which begins to change to sorrel tops in May and June and to red tops in July and August. The finding of these conditions within the region occupied by this species will indicate destructive work by barkbeetles, but 'positive evidence of the presence of this species can only be determined by cutting into the bark and finding the characteristic galleries and mines occupied by authentically identified beetles. As a rule, the broods have left the trees by the time the leaves are all dead, and sometimes before the leaves have changed from yellow or sorrel to red. Exceptions are frequently -found when but one side or the top of a tree is killed the first year and the remaining living bark is infested with broods of the next. It is safe to conclude, however, that after the leaves are all dead and brown, very few living examples of this species will remain in the bark. EFFECTS ON COMMERCIAL VALUE OF THE WOOD. Owing to the thick sapwood of the western yellow pine, the com- mercial value is reduced for certain purposes by a bluing condition, which affects it soon after the trees are infested by the beetles in August and September and long before the leaves begin to fade. The heartwood of large trees is not usually reduced in value for several years after the trees die, provided they do not suffer from subsequent injury by storm, fire, wood-boring insects, or premature decay. If left standing, however, with the bark on, until the branches and tops begin to fall, the loss from decay may be complete. On the other hand, if the bark be removed from the trunks of the standing trees, the heartwood will remain sound for many years longer. The danger, however, of the total destruction of the dead timber by forest fires is so great that in order to insure against such losses, and at the same time destroy the broods of insects, the insect-killed timber should be utilized before the insects emerge. * FAVORABLE AND UNFAVORABLE CONDITIONS FOR THE BEETLE. Favorable conditions for the multiplication and destructive work of this species are found in somewhat isolated forests with a predomi- nance of large mature timber. Unfavorable conditions for destruc- tive outbreaks will be found in forests, isolated or not, which are kept under a system of forest management or regulations which provide for the utilization of the mature timber and the barking; of trees injured by lightning or dying from any cause, before the broods of insects develop in the bark and emerge. 89535— Bull. 83, pt. 1—09 S 98 THE SCOLYTID BEETLES. METHODS OF COXTEOL. Whenever it is positively determined that this species is attacking living pine timber in a given locality and that the bark of living and dying trees contains living parent adults or developing broods, active and radical measures should be promptly adopted for its control. The simple removal of the infested bark from the main trunks of the trees, without burning it, is sufficient to kill the broods of this species, provided the work be done between the first of October and the first of June. If, in the case of a mod- erate outbreak, the larger clumps or patches of infested trees and the more accessible scattering ones in the worst affected sections of a forest are thus treated, it should serve to bring the pest under control the first year, but in the case of a very extensive out- break this may require two or three years or more. If all of the infested trees can be barked or utilized and the slabs burned without much additional ex- pense, it may be best to do so, but where, for any reason, this can not be done within the specified time, the work should be planned so as to in- sure the barking or utilization of all of those in the larger patches, or an aggregate of 75 per cent of the in- fested trees to each square mile. If the bark be removed from the standing trees (figs. 57, 58), an aggregate of 75 per cent or more of the actually infested bark should be removed from all of the trees, or all of the infested bark should be removed from 75 per cent of the trees. The work should be planned and conducted with the object of destroying the greatest possible number of insects for the labor and time expended. That is, if there are more infested trees than can be barked within the specified time, and five or six times as many insects can be killed by removing half of the infested bark from the standing trees as can be done in the same time by felling one tree and removing all of the bark, the former is far pref- erable, remembering that it is not necessary to exterminate the enemy, Fig. 57.— Removing bark from trunk of standing tree with special barking tool having handles of different lengths, to destroy broods of the Black Hills beetle. (Original.) THE GENUS DENDROCTONUS. 99 but that it is necessary to reduce its numbers beyond the power of doing harm. The removal of the infested bark from at least the lower half of the standing trees offers many advantages over felling the trees for the purpose of barking all of the trunk. More insects can be destroyed in the standing trees within a given time and the barked standing timber may be left standing until suitable facilities can be provided for its utilization; thus, if necessary, all of the specified time for the destruction of the in- ■Mji , ^ V,^^" " W^Vv ^^■v—^ ■ £wE&, lv M 0 1 / H p| fc m T^' ji£ufij & ■ ^K| i-'^,, \ mm ^ll^^ww'mjB :'r^ ' V' r"*^T fH EljM^ljf-- L ■ JP* ^Htg; ■ . fl H Kt| |;l ■fc f'ifl5JJ^K|5 "■ ' ' mi^BB Bill in m '-1 ,-'* f ; ;r:i , 1:1 <-- £ ^25HHp9? "; ,--• ;|^HEr-f?r ■ S8i^8 pg «*** sects may be devoted exclusively to the re- moval of the bark. The barking of newly attacked trees in Au- gust and September is not to be recommended for this species. Trap trees are of little or no service in combating it and continued timber- cutting operations ap- pear to have little or no influence in check- ing its ravages on liv- ing timber. Recent reports of conditions in the vicin- ity of Colorado Springs, where a large percent- age of the infested tim- ber was barked in 1905 and during the winter and spring of 1906, in- dicate most successful and satisfactory re- sults. (See also other references to successful control, pp. 36-38.) The depredations in the Black Hills have been so extensive that little or nothing has been accomplished toward the control of the beetle, owing to lack of sufficient funds and other facilities for adopt- ing the radical measures necessary to accomplish anything of im- portance. (For additional information, see Bulletin No. 56, Bureau of Ento- mology of which the above is a partial revision.) Fig. 58.— Removing bark from base of trunk of standing tree with special barking tool, to destroy broods of the Black Hills beetle. (Original.) 100 THE SCOLYTID BEETLES. BASIS OF INFORMATION. The data on this barkbeetle have been secured through investiga- tions by the writer in the Black Hills National Forest, September, 1901, August, 1902, and June, 1903; at Vermejo, N, Mex., May, 1903; at Flagstaff, Ariz., May, 1904; in the Pike National Forest and in the vicinity of Colorado Springs, Colo., October, 1905, and June, 1906, and in the vicinity of Fort Garland, Colo., June, 1906; by Mr. J. L. Webb, in the Black Hills National Forest, South Dakota, May to October, 1902, and April to September, 1906; in the Chiricahua National Forest, Arizona,. June to September, 1907; by Mr. H. E. Burke, at Nemo, S. Dak., November, 1904; at Kamas, Panguitch, and Panguitch Lake, Utah, June to September, 1907; by Mr. W. D. Fig. 59.— The Black Hills beetle: Distribution map. (Author's illustration. Edmonston, at Larkspur, Colo., July, 1906; at Brookvale, Sequache, Poncha Springs, San Juan National Forest, Wagon Wheel Gap, Coche- topa National Forest, Monte Vista, White River National Forest, Uncompahgre National Forest, and Colorado Springs, Colo., January to December, 1907; in the San Isabel National Forest, at Halms Peak and Clarke, in the Gunnison National Forest, the Hayden National Forest, the La Salle National Forest, the Ouray National Fort^t. the Pike National Forest, the Routt National Forest, the San Juan National Forest, the Wet Mountains National Forest, and the White River National Forest, Colorado (12 national forests), and at Encamp- ment and Downington, Wyo., in 190S. Additional localities through correspondence and other collections are Palmer Lake, Cat Mountain, Trinchera Estate, Fort Collins, Pine, and the Medicine Bow National THE GENUS DENDROCTONUS. 101 Forest, Colorado; Fredonia, Ariz. ; Kanab, Escalante, Provo, Aqua- rius National Forest, Utah, and at Keystone, Wyo. It is repre- sented in the forest-insect collection of the Bureau of Entomology by more than 10,000 specimens. BIBLIOGRAPHY. Hopkins, 19026, p. 10; Hopkins, 1902c, p. 21; Hopkins, 1903a, p. 59; Hopkins, 19036. pp. 275-282; Hopkins, 1904, pp. 41, 43, 44; Hopkins, 1905, pp. 1-24; Hopkins, 1906 p. 4; Hopkins, 1907, p. 162; Hopkins, 1909, pp. 109-114. No. 11. THE JEFFREY PINE BEETLE. (Dendroctonus jejreyi Hopk. Figs. 60, 61.) The Jeffrey pine beetle is a stout, black, cylindrical barkbeetle 6 to 8 mm. in length; the head broad, convex, with faint grooves behind and usually in front of the mid- dle; the prothorax stout, broad, shining, the sides suddenly nar- rowed toward the heatl and the punctures fine ; the elytra with mod- erately coarse rugosities between the rows of punctures, which are distinct on sides, the declivity with a few long hairs, the striae on grooves narrow, and the interven- ing spaces broad and roughened with coarse granules. (See fig. 60.) It attacks living and dying Jeffrey pine and yellow pine, in the Yosemite National Park and San Bernardino County, California. It excavates long, nearly straight, egg galleries through the inner bark, and grooves the surface of the wood; the larval mines extend from the sides, exposed in the inner bark. The stout, whitish, grublike larvae trans- form to pupae and adults in cells at the end of the burrows, and the broods occupy the bark on the main trunk. The infested trees are indicated by pitch tubes on the trunks in the summer and fall, and during the following Ma}^ to August by the fading and yellowish foliage. Fig. 60.— The Jeffrey pine beetle {Dendroctonus jeffreyi): Adult, Greatly enlarged. (Au- thor's illustration.) 102 THE SCOLYTID BEETLES. SEASONAL HISTORY. OVERWINTERING STAGES. The winter is passed in the bark on trees attacked the previous summer, as parent adults, larvse, and developed broods of young adults. ACTIVITY OF OVERWINTERED BROODS. The spring activity of the overwintered broods appears to be similar to that of species 9 and 10. It appears that the overwintered broods begin to emerge from the dying trees toward the last of July, and to enter the bark of other trees to excavate their galleries and deposit eggs, but many, and perhaps the majority, of the overwintered broods Fig. 61. — The Jeffrey pine beetle: Distribution map. (Author's illustration.) do not emerge until after the middle of August. Some of the broods of the first generation probably develop before cold weather, but it is not likely that any of them emerge before the following July. HABITS. The habits of this beetle appear to be quite similar to those of the mountain pine and Black Hills beetles. Therefore, while the details of its seasonal history and habits remain to be worked out, enough is known to show that it is a dangerous enemy of the Jeffrey and yellow pine, and that it will in all probability attack other pines within its range. Since the above was written the insect has been found to be quite destructive to the Jeffrey and western yellow pine in northern California. THE GENUS DENDKOCTONUS. 103 METHODS OF CONTROL. From what is known of the life history and habits it is evident that practically the same methods recommended for species 9 and 10 may be adopted for the successful control of this species. BASIS OF INFORMATION. Information on this species is based on investigations by Mr. H. E. Burke in July and August, 1906, along the rims of Little Yosemite and Yosemite, California, and*by Mr. V. S. Barber, at Sterling and Chester, Cal., in 1907. Additional localities through correspondence are Nevada City, Tallac, Pinogrande, and San Bernardino, Cal. This species is closely related to the mountain pine and Black Hills beetles, but is quite easily distinguished from them by the slightly more elongate, shin- ing, and finely punctured prothorax. ^ \|^ | BIBLIooRApH;. _-^_: i Hopkins, 1909, pp. 114-116. No. 12. THE EASTERN LARCH BEETLE. (Dendroctonus simplex Lee. Figs. 62-64.) The eastern larch beetle is a stout, reddish to reddish-brown, cylindrical barkbeetle, 3.5 to 5 mm. in length, with broad, convex head, the prothorax short and strongly narrowed and constricted toward the head, the elytra with coarse rugosities between rows of indistinct punctures, the declivity convex and rather deeply grooved, the spaces be- tween rather convex, and the body sparsely clothed with rather long hairs. (See fig. 62.) It attacks injured, dying, felled, and living eastern larch, from New Brunswick, Canada, westward to northern Michigan, and probably to the western and northern limit of this tree, and south in the higher Alleghenies to northeastern West Virginia and western Maryland. It excavates long, slightly wind- ing egg galleries in the inner bark (fig. 63) and grooves the sur- face of the wood. The eggs are placed in alternate groups of three to six, or more, along the sides of the galleries. The short and broad, or sometimes long larval mines extend at right or oblique angles, and are exposed in the inner bark. The stout, whitish, grub- like larvae transform in separate cells at the ends of the burrows in Fig. 62.— The eastern larch beetle (Den- droctonus simplex): Adult. Greatly enlarged. (Author's illustration.) 104 THE SCOLYTID BEETLES. the inner bark. The broods occupy the bark of stumps and logs and the trunks of standing trees from the ground to the branches, or on into the tops. Fresh attacks on living trees cause a flov of resin or red boring dust in the loose bark and around the base of the trees. This species is capable of extensive depredations on the largest and best larch, but apparently prefers to infest injured, dying, and felled trees. Fig. 63.— The eastern larch beetle: Egg galleries and larval mines. (Author's illustration.) SEASONAL HISTORY. While comparatively few details on the seasonal history of this species have been determined, it is evident that it passes the winter, principally in the adult stage, beneath the bark of trees, stumps, etc.. attacked during the preceding summer, and activity begins with the first warm weather in April. May. or June. It also appears that there is but one generation annually, and. owing to the almost com- plete development of the broods in the fall, there is probably not THE GENUS DENDROCTONUS. 105 much overlapping of the overwintered and new broods during the summer. The broods of the first generation begin to transform to adults toward the last of July, at which time all stages from parent adults to freshly transformed ones have been found. ECONOMIC FEATURES. Sufficient observations have been made to indicate that under favorable conditions this may be a very destructive species. Like most of its relatives, it attacks the largest and best trees, and when aided by defoliating insects, like the larch worm, or by other bark- beetles and bark-borers, it could easily devastate large forests. It is evident, however, that its preference for the bark on the stumps and logs of felled trees and those injured and dying from other causes renders it much less dangerous than most of the other species, and also much easier of control when it does attack the living timber. Favorable conditions for its destructive work will be found in large forests of old matured larch undisturbed by the lumberman, where many trees have been defoliated by the larch worm or injured by fire, storms, etc., while unfavorable conditions for its work on the living timber will be found in sections where continued timber-cutting operations are carried on under a system of management requiring the utilization of the older living larch timber, as well as any that is dying or found to be infested with the beetle, as also when proper care is taken of the young timber to facilitate a vigorous healthy growth. METHODS OF CONTROL. Whenever it is positively determined that the larch is seriously injured or dying from the ravages of this species, the infested trees should either be barked, burned, or placed in water, and the stumps barked, during the period between September and the following May. Trap trees felled during May and June should serve to attract the beetles away from living trees and thus facilitate their destruction by removing the bark during the following fall and winter. BASIS OF INFORMATION. Information regarding this barkbeetle is based on investigations by the writer in northeastern West Virginia and northwestern Mary- land, near Cranesville, W. Va., May, 1897, in northeastern Maine, June, 1900, and in northwestern Michigan, July and August, 1907, and by Mr. W. F. Fiske in northwestern Michigan, October, 1906. It is represented by more than 150 specimens in the West Virginia Agricultural Experiment Station collection and by 180 specimens in the forest-insect collection of the Bureau of Entomology, 106 THE SCOLYTID BEETLES. This species is easily separated from its nearest relative, the Doug- las fir beetle, by its smaller size and eastern distribution, and from eastern forms by its medium size, convex and deeply grooved declivity, the character of its gallery, and its occurrence in larch. % v. i i -J.J — r J Fig. 64. — The eastern larch beetle: Distribution map. (Author's illustration.) BIBLIOGRAPHY. Schwarz, 1888, p. 175; Packard, 1890 (under Dendroctonus sp.?), p. 903; Harring- ton, 1891, p. 27; Hopkins, 18986, pp. 104-105; Hopkins, 1899a, pp. 394, 447; Hopkins, 1909, pp. 117-121. Xo. 13. THE DOUGLAS FIR BEETLE. {Dendroctonus pseudotsugx Hopk. Figs. 65-69.) The Douglas fir beetle is a stout, reddish to blackish-brown, cylin- drical barkbeetle, 4 to 7 mm. in length, its head broad, convex, with shallow longitudinal groove behind the middle; the prothorax short, broad, punctured, with sides somewhat rounded and strongly nar- rowed and constricted toward the head; the elytra with rather coarse rugosities between the rows of punctures; the declivity convex, with striae deeply grooved and intervening spaces convex and nearly smooth or roughened, and the body with numerous long hairs. (See fig. 65.) It attacks injured, dying, felled, and living Douglas fir, bigcone spruce, and western larch, wherever these trees grow from British Columbia southward into Xew Mexico, Arizona, and Cali- fornia. It excavates long, straight, or slightly winding egg galleries through the inner bark, and grooves the surface of the wood, the eggs being placed in alternate groups along the sides; the long larval THE GENUS DENDROCTONUS. 107 mines extend at right angles from the main galleries and are exposed in the inner bark, often marking the surface of the wood (figs. 66, 67, 68). The stout, whitish, grublike larvae transform to pupa3 and adults in cells, either exposed or not, in the inner bark. The broods usually work independently of the other species, and often occupy and separate the bark on the lower to middle trunks of standing and felled trees. The fresh attack on living or freshly felled trees is indicated by red borings at the entrance to the galleries and lodged in the loose bark on the trunk or around the base; the leaves of the dying trees fade, turn pink- ish yellow, or remain green in the fall succeeding spring and summer attack, but turn brown during the winter and spring. SEASONAL HISTORY. OVERWINTERING STAGES. The winter is passed in the inner bark of trees, logs, etc., attacked the preceding spring and summer, principally as developed broods of adults, but also as young to matured larvae and probably parent adults. ACTIVITY OF OVERWINTERED BROODS. Activity begins during the first warm weather in April, when the parent adults ex- tend their galleries and de- posit eggs. The young adults of the developed broods be- gin to emerge by the middle of April, and continue to come out during June or July or later. The overwintered, large larvae evidently complete their development and emerge by the first of August, while the broods of young larvae of the possible second generation from eggs deposited in the fall evidently complete their development and begin to emerge in August, and continue to do so until cold weather, when some will begin their second hibernation as fully developed broods of adults. Fig. 65. — The Douglas fir beetle (Dendroctonus pseudo- tsugse): Adult. Greatly enlarged. (Author's illustra- tion.) 108 THE SCOLYTID BEETLES. GENERATION. The~ overwintered broods of adults begin to attack the trees, excavate new galleries, and deposit eggs about the middle of April. The principal attack is during April, May, and June, but may con- tinue into July or later. The eggs begin to hatch soon after they are deposited, and the larvae begin to feed and continue to develop during May, June, and July, into August or later, some retarded individuals continuing to feed until cold weather. They begin to transform to pupae and adults during the latter part of July and continue their transformations during August until hibernation begins. There is some evidence that a few of the more advanced broods may emerge during September and October and deposit eggs for the second generation during September and October, but it is probable that these late-emerging broods are in the majority of cases those developed from overwintered broods of young larvae or from eggs deposited in the spring by overwintered parent adults. It is very evident, however, that there is quite a complete develop- ment of the first generation before the first of October, which accounts for the passing of the winter principally as fully developed adults. HABITS. This species prefers to infest the stumps and logs of felled trees, and injured and dying standing ones, in which it breeds in great numbers, but in some localities and under favorable conditions it will attack healthy living trees and cause their death. So far as known, it breeds exclusively in the Douglas fir, bigcone spruce, and western larch. The trunks of standing trees from a foot in diameter to the large older ones are attacked from the ground to the middle portion of the trunk, and sometimes to the lower branches. The stumps, logs, tops, and larger branches of felled trees are favorite breeding places and are usually thickly infested. The parent adults enter from the crevices and depressions in the bark, excavate entrance burrows through the outer and inner bark, and then extend their long, longitudinal egg galleries through the inner living or dying bark. As the gallery is extended, the female places her eggs in alternate groups along the sides, and when one gallery is completed she either remains in the gallery until she dies or leaves it to excavate a new one. The larvae, upon hatching, begin to feed on the inner bark and to extend their food burrows at right or oblique angles to the mother gallery. Instead of the burrows being short and broad like those made by many other species, they are often extended to a length equaling or exceeding that of the mother gallery, and cross each other in such a manner as to completely girdle the tree and separate the bark so that it is easily removed from THE GENUS DENDROCTONUS. 109 the wood. The larvae transform to pupae and adults in individual cells at the ends of their burrows, and when the adults are fully matured they bore through the intervening bark and congregate in broad cavities beneath the bark, remaining thus over winter, and until they begin to emerge in the spring. Their habit of flight is not wTell known, but they evidently fly or swarm in the evening or early part of the night. Fig. 66.— The Douglas fir beetle. Egg galleries and larval mines: a, Beginning or basal sections of egg galleries in bark; b, entrance; c, egg gallery; d, ventilating hole; e, egg nest; /, abnormal branch; g, larval mines; h, egg gallery packed with borings; i, subsequent passage or inner gallery through borings. (Author's illustration.) ECONOMIC FEATURES. The preference shown by this species for the bark of logs and stumps of felled and injured trees makes it of less economic impor- tance than the Black Hills beetle and some of the other species, but in some of the localities, especially in Idaho and southward to southern Colorado and northern New Mexico, it attacks the living timber and causes extensive losses of the best as well as of the inferior Douglas fir. EVIDENCES OF ATTACK. The first evidence of attack on living trees is the appearance of reddish boring dust in the crevices of the bark, lodged in the loose bark on the trunk and around the base, and on the ground around 110 THE SCOLYTID BEETLES. its base, which is the only external evidence of attack or infestation until in the fall and winter, when the leaves on some of the trees will begin to fade and turn pinkish or yellowish, while on other trees they will not begin to change color until next spring, and on still others only the leaves of the top or lower branches on one side of the crown will die, while the remainder will continue green, thus indi- cating that only a portion of the bark is killed and infested. TVhile the fading and dying of the leaves result from infestation by this beetle, this may, and does, sometimes result from other causes, so that the only positive evidence of injury or destruction of Douglas Fig. 67. — The Douglas fir beetle. Egg gallery and larval mines: a, Egg gallery in bark and grooved in surface of Avood; b, larval mines in bark: c, larval mines marked and slightly grooved on surface of wood. (Author's illustration.) fir or western larch in any locality by this species can be determined only by cutting into the bark of the freshly attacked or dying trees and finding the characteristic galleries and larval mines occupied by authentically identified parent beetles or their broods. As a rule, the broods leave the trees before the leaves have turned reddish brown or fallen, and they never return to the trees to excavate galleries and deposit eggs for new broods after all of the bark is dead, since they must have either living or partially living bark for their eggs and young larva?. THE GENUS DENDROCTONUS. Ill EFFECTS ON COMMERCIAL VALUE OF THE WOOD. The commercial value of the Douglas fir trees killed by the beetle is not seriously impaired for several years after they die, except that the sapwood discolors and otherwise deteriorates, but the heartwood of large trees may remain sound for twenty years or more. On the other hand, if they are seriously attacked by wood-boring insects the wood may deteriorate rapidly. FAVORABLE AND UNFAVORABLE CONDITIONS FOR THE BEETLE. Favorable conditions for the multiplication and de- structive work of this bark- beetle ace found in the drier regions, where the growth of the trees is slow and where the older trees are frequently injured by fire, storms, land- slides, etc., as also in the more isolated sections of the forests in such a region where no continued timber-cutting operations are carried on. Unfavorable conditions for attack on living timber are found in moist regions, where the growth of the trees is vig- orous, as in the coast, Cas- cade, and Sierra sections of Washington, Oregon, and California, and especially in those sections in which con- tinued timber-cutting opera- tions are carried on under a system of lumbering or forest management which requires that the matured or older timber, as well as that which is dying and " beetle infested," be taken out, and where the younger, vigorous timber is protected from injury by fire and other causes. METHODS OF CONTROL. Whenever in a given locality it is positively determined that this species is attacking and killing the Douglas fir, bigcone spruce, or western larch, and that the bark of living and dying trees contains Fig. 6S.— The Douglas fir beetle: Section of log with bark removed, showing brood galleries marked and grooved on surface of wood. (Author's illustration.) 112 THE SCOLYTID BEETLES. living parent adults or developing broods, efforts should be made toward its control. The individual trees and groups of trees attacked during the spring and summer should be located and marked during August and November. In order to effectively check its ravages, at least 75 per cent of the infested trees should have the infested bark removed from the main trunks or the logs converted into lumber and the slabs burned during the period beginning with the first of November and ending with -the first of the following March. The simple removal of the bark during this period, without burning it, will be sufficient to kill the broods. The bark may be removed from the trees as they stand or after they are felled, as may in each case be most convenient or desirable. The operations should be confined first to the worst infested locali- ties and to the larger clumps of infested trees. Therefore -explora- tions should be made from time to time to determine the principal localities in which the ravages of the insect are sufficiently extensive to require special attention. If it is more convenient or practicable to fell the trees and roll the infested trunks together and burn them, the work should be done during the winter months. With this species the barking of newly infested trees during July and the first half of August is permissible and sometimes desirable, because this is the period in which the principal larval development takes place and before the broods of adults have sufficiently matured to fly when liberated from the bark. By the last of August some of the adults have developed sufficiently to fly; therefore the infested trees should not be barked during the latter part of August and through September and October. The fact that this species is attracted to the living bark on the trunks and stumps of recently felled trees suggests the efficiency of the trap-tree method of control. Whenever it is found desirable to adopt this method living trees should be felled in August and April and have the bark removed or the logs utilized and the slabs burned to kill the broods, the former during the winter months and the latter during the following July and the first half of August. Experiments with girdled trap trees show that girdling is by no means as effective as felling. Continued timber-cutting operations within a given locality, espe- cially in the coast region, usually serve to protect the living timber from attack by this beetle, because the stumps, logs, tops, and broken or injured Douglas fir trees furnish all the requirements for its breeding, and the utilization of infested logs destroys large num- bers of the beetles. If, however, the living timber in the vicinity of cuttings should at any time become threatened by an invasion from the cuttings, or if it be desirable to include in timber-cutting THE GENUS DENDROCTONUS. 113 regulations certain provisions for the burning of the slash, this work should be done during the period beginning about the first of October and ending by the first of March. BASIS OF INFORMATION. The informatio'n relative to this beetle is based on investigations conducted by the writer at Guerneville and McCloud, Cal., Grants Pass, Corvallis, Newport, Detroit, and St. Helen, Oreg., Port Angeles and Port Williams, Wash., Sand Point, Kootenai, and Hailey, Idaho, April and June, 1900; at Kootenai, Idaho, and Junc- tion, Wash., August, 1902; at Tercio, Colo., and Fieldbrook, Cal., May, 1903; at Colorado Springs, Colo., October, 1905, and at Fort Garland, Colo., in 1906; by Mr. H, E. Burke, at New London, Eock Fig. 69. — The Douglas fir beetle: Distribution map. (Author's illustration.) Creek, Kent, Satsop, Hoquiam, North Bend, Pialschie, Des Moines, Ashford, and Meredith, Wash., May to October, 1903, June to Sep- tember, 1904, May to September, 1905, and April and May, 1906; at Smiths Ferry, Idaho, October, 1904; in San Mateo County, Cal., May, 1906; at Panguitch and Panguitch Lake, Utah, July to Sep- tember, 1907; by Mr. J. L. Webb, in the San Francisco Mountains, Arizona, June, 1904; at Centerville, Stites, Kooskia, and Pioneerville, Idaho, from June to September, 1905; in the Chiricahua National Forest, and the Sacramento National Forest, Arizona, June to Sep- tember, 1907; by Mr. W. F. Fiske, at Capitan and Cloudcroft, N. Mex., March to June, 1907. Additional localities through corre- spondence and from other collections are Belton, Ovondo, Bozeman, Kalispell, and Leavenworth Valley, Mont. ; Orting and Dole, Wash. ; 89535— Bull. 83, pt. 1—09 9 114 THE SCOLYTID BEETLES. Santa Fe, N. Mex. ; Henrys Lake National Forest and Beaver Can- yon, Idaho; Ventura County, CaL, and Vancouver, British Columbia. It is represented in the forest-insect collection of the Bureau of Ento- mology by more than 700 specimens, including all stages and work. BIBLIOGRAPHY. Hopkins, 18996 (under D. similis), pp. 10, 11, 15, 21, 22, 26; Hopkins, 19016, p. 67; Hopkins, 1903a, p. 60; Hopkins, 1904, p. 19; Hopkins, 1905, pp. 10, 11; Hopkins, 1906a, p. 4; Hopkins, 1909, pp. 121-126. No. 14. THE EASTERN SPRUCE BEETLE. (Dendroctonus piceaperda Hopk. Figs. 70-77.) The eastern spruce beetle is a reddish-brown to black barkbeetle, 5 to 6 mm. in length, the body sparsely clothed with long hairs, the head broad and convex, the pronotum often darker than the elytra, with the sides distinctly narrowed and constricted toward the head and the punctures of irregular sizes and moderately coarse, the elytra with coarse rugosities between rows of indistinct punctures, and the elytral declivity somewhat flattened, smooth, and shining in the male, more convex, roughened, and less shining in the female. (See fig. 70.) It attacks the red, black, and white spruce from New Brunswick, Canada, southward in the mountains of New York and Pennsylvania, and westward to Michigan. The adult bores through the outer bark to the inner living portion, extends its egg gallery (figs. 71, 73) lon- gitudinally through the inner bark, and grooves the outer layers of wood (fig. 72). From ten to thirty or more eggs are deposited close together in elongate cavities in the . sides of the egg gallery. The larvse soon hatch and begin to feed on the bark. At first the larval mines are usually connected, forming a common cavity, but later each larva excavates an independent mine, which it ex- tends in a generally transverse but irregular course from the egg gallery, with the transformation cell at the farther end in the inner bark or between the inner and outer bark; but, like their larval mine, this is usually exposed on the inner surface. The presence of this insect in standing living or dying trees is indicated by reddish boring-dust in the crevices of the bark, by pitch or gum tubes, and by the fading and falling of the leaves, or by the bare reddish ap- pearance of the twigs. It is a very destructive enemy of mature red and white spruce. SEASONAL HISTORY. (See fig. 75.) OVERWINTERING STAGES. The winter is passed in the inner bark of trees in which the insect developed the previous summer, as adults and all stages of larvae. THE GENUS DENDROCTONUS. 115 ACTIVITY OP OVERWINTERED BROODS. There is some evidence that a few parent adults hibernate in gal- leries started the previous fall and that they may begin activity some- Fig. 70.— The eastern spruce beetle (Dendroctonus piceaperda): 1, 2, Adult, dorsal and lateral aspects; 2a, 2b, $ , 9, details of adult; 3, pupa; 3a, lateral aspect of head and prothorax of pupa; h, larva; ha, hb, he, details of larva. All greatly enlarged. (Author's illustration.) what earlier than the overwintered broods. The overwintered, de- veloped adults begin to emerge about the middle of June and con- tinue emergence until August, or later, the principal emergence taking place during July. They begin to attack the trees and exca- vate galleries soon after they emerge, and by the 19th of June begin 116 THE SCOLYTID BEETLES. to deposit eggs. The work of excavating galleries and depositing eggs is principally during June and July, but may be continued until September, or later (as evidenced by the finding of young larvae in October, and the same, after overwintering, the following May.) Fig. 71. — The eastern spruce beetle. Egg gallery and larval mines: a. Egg gallery; b, boring dust packed in gallery; c, entrance and subsequent or inner gallery: d. larval mines. (Author's illus- tration.) The overwintered broods of larva? begin activity during the last week in May and first week in June. The matured larva? begin to transform to pupa? and adults during the first week in June, and con- tinue to do so, while the younger larva? are developing, until July or later. All have evidently transformed and emerged by the middle of August, or earlier. THE GENUS DENDROCTONUS. 117 GENERATION. The eggs deposited by the overwintered broods of adults begin to hatch during the latter part of June (fig. 72) and the first part of July, and continue to hatch during July and August. The larval de- velopment is confined principally to July and August, but may con- tinue to October. The more advanced larvae begin to transform to pupae and adults during the last week in August and first week in Sep- tember, and continue to do so until hibernation begins in the fall. No evidence has been found that any of the broods emerge from the trees in the fall; therefore there is but one generation annually. By far the greater number of the broods pass the winter as young to matured adults, and the hiber- nation begins about the middle of October. HABITS. This species prefers to attack the older mature living timber. It also attacks standing tim- ber weakened or injured from other causes, and trees felled by storm and otherwise, though usually not in such r ^ r1 3 5 * A I i. **%*£%* 3 i c : e §- j - * i i 4 2 < C/; p if sz -i r* P !» t» i B P S »- o P a" o> So o O; B d p 0 °i I 3 N>P r+ \ &5 P P <1 3 4 Cu O- c" P o ? 5 jl CD O r J?5 CD o ^ i* CK Cj; a If O o, 53 3 2 o 1? s P § CD CD t); P -Jl r if 3 1 ; t; ® ! s G-4 CD CD o® ! -1 c? O® ! 4 1 • •d t O® ! ! • • k _ ® ! &\ t . . o s o, > ! !/>% • • o o p- S b ! ! •** "! • • o o o ?> i: © ! ! •! ••oooo p *r M ! •• • • o o o oC £• ^ ~ £ • • o«»oob OOC 1: * % % • .oo«ooo OOOC o, / ! • • ooooooo OOOS ) ^ p £y% • • o o o O o o o 000®(« ) ^> o" 3 /% ••ooooooO0OO®00IH <^> £/% • • o oooooO00O000t#H >P S6> '/% '.oooooOO®©®®©©!!!!! £" ^5 ! . . o o ooOOO®®®!®®!!!!!! s **F /m • . o o oooOO®®®!!®!!!!!!4 t~ 3 m . . o o o o OOO® ©©!!!!!!!!!!< is IN * • • o o o ooOO©@®!!!!!!!!!!!< H -t • • o o o o 6OO®0®!!!!!!!!!!!!I r ^g • o o OOOOO00®!!!!!!!!!!!!!! \i s^ 118 THE SCOLYTID BEETLES. Fig. 73.— The eastern spruce beetle: Old egg galleries and larval mines in bark. (Author's illustration.) THE GENUS DENDROCTONTJS. 119 numbers as it does the living, standing trees. It infests the red spruce, black spruce, and white spruce, but, so far as known, does not attack any of the pines or the larch. The beetles enter the bark of healthy trees at a point from 6 to 10 feet from the base, and that of trees weakened by disease or other causes from near the base to the larger branches. In the living trees the entrance burrow is gradually extended obliquely upward, or subtransversely, thence in a longitudinal direc- tion upward through the inner bark and often grooving the surface of the wood. Along the sides of this gallery, which is usually about three times as broad as the beetle, the eggs are placed singly in small cavities or in groups in an elon- gated cavity. The eggs are then protected by a mass of borings, closely packed and cemented with gum, which, with the exception of a small inner burrow or subgallery, fill up the broad egg gallery. The original entrance is first packed; then an opening to the outside is made in the roof of the gallery a few inches from the entrance, an- other section is excavated and packed, another hole is made through the roof, and so on until the gallery is completed. After all is finished the adults make one or two short, irregular, lateral branches at the farther end, ap- parently for an abiding place until they die. The gum flowing into the wounds made by the beetles when they are excavating the entrance is pushed out and the holes kept open through it, thus forming the pitch tubes, which are so conspicuous on the bark of freshly attacked trees. After the vitality of a tree is weakened by numerous wounds and by an excessive flow of resin the subsequent entrances are not marked by pitch tubes. Or, if a tree is decidedly weakened from other causes before it is attacked, or when a large number. of beetles is boring into the outer bark, and the boring-dust falls down and lodges in the flakes of bark and in the moss on the tree, pitch tubes are not formed. Fig. 74.— The eastern spruce beetle. Old gal- leries marked on surface of tree: Grooves on surface of wood of tree that has been dead about twelve years. ( Author' s illustration. ) 120 THE SCOLYTID BEETLES. When the eggs hatch, the minute white grubs or larvae eat their way into the soft inner bark, which by this time has commenced to die and is in the best condition for their food supply. When the eggs are deposited in separate cavities, each larva makes a separate mine, but when they are massed along the sides, or placed close together, as they usually are, the larvae work side by side and consume all of the inner layer of bark until they have progressed some distance, when they begin to separate and each larva makes an independent mine. While the individual burrow may cross and recross its neighbor, it preserves a course of its own and increases in width as its occupant increases in size, until the larva ceases to feed. The latter then excavates a cavity, either in the bark next to the wood or next to the outer dry bark, where in due time it changes to the pupa. Here it remains in a semidormant condition until the legs, wing covers, and other parts develop. It then sheds its outer skin and becomes an. adult winged beetle, soft and yeUow at first, but gradually hardening and becoming darker. When the individuals of a brood are fully matured in the spring, they bore through the inner bark between the transformation cells and congregate in the larger common chamber thus formed until it is time for them to emerge. They then bore their way out to the surface and emerge to fly in search of suitable trees in which to exca- vate galleries and deposit eggs. Scarcely anything is known of the flight habits, but the beetles probably fly during the evening or at night. ECONOMIC FEATUKES. CHARACTER OF ATTACK AXD INJURY. So far as known, tins beetle confines its attack to the spruce in the region north of latitude 43°. Toward its southern limit it evidently does not occur at altitudes below 2,000 or 2,500 feet, while at latitude 47° in Maine and in extreme northern Michigan it would be found below an altitude of 600 feet. It is rarely found in trees under 10 inches in diameter breast high, but prefers those IS inches or more in diameter. Whenever it occurs in sufficient numbers to attack and kill large numbers of trees the hying beetles within a given locality usually concentrate on groups or patches of timber of greater or less extent. The trees die from the attack, and when the new broods develop they emerge from the dying trees and settle on the living timber in another locality, and so on, until all of the matured timber is killed. They usually settle on a tree and enter the bark in such numbers that there is little chance for its recovery. Their numerous egg galleries are extended through the most vital part of the tree (the cambium), where the new growth of wood and bark takes place. Thus the injury produces a weakened condition of the tree. This is THE GENUS DENDROCTONUS. 121 Fig. 75.— Balsam fir chips showing annual growth, indicating dates of death of spruce trees. 1, From tree hy dead spruce in cutting of about 1888; 2, from tree standing by dead spruce in old cutting of about 1886; 8, from tree standing by dead spruce which showed the work of the eastern spruce beetle (tree evidently died about 1888); A, from fir in blow-down of about 1871, which was followed by another in about 1885-6; 5, from tree in blow-down of about 1886; 6, from spruce standing by large spruce tree which was broken by a storm of about 1886 (evidence was found in this tree that it was living when felled and that it had been attacked, after falling, by the eastern spruce beetle; both galleries and remains of beetles were found in the bark); 7, section of small suppressed spruce about forty-five or fifty years old. All natural size. (Author's illustration.) 122 THE SCOLYTID BEETLES. followed by the lateral extension of the larval mines of the young broods, which serves to completely girdle the tree and kill the inner bark, and this in turn is followed some months later by the gradual or sudden dying of the leaves and the complete death of the tree. The trees on which a successful attack is made in June or July will have the leaves faded and fallen by October, but the leaves on those attacked in August or later may remain normal until the following May or June before the}' fall. EXTENT OF DEPREDATIONS. The evidence we have been able to collect shows that at various times during the past century this beetle has been the cause of the death of an enormous amount of the best matured spruce timber in the forests from New Brunswick to northern New York and in places in Canada. It is also evident that it will continue to be a menace to standing matured timber, probably throughout the region in which the red and white spruce prevail in forest growth. In a report by C. W. Johnson (1898, pp. 73-74), reference is made to extensive destruction of red spruce in the mountains north of Stull, Wyoming Count}", Pa., supposed to have been caused by a Dendroc- tonus identified as D. rufipennis. Specimens collected by Mr. Johnson have been examined by the writer and found to be D. piceaperda. Mr. Johnson stated that some 5,000,000 feet of spruce had been killed on the lands of one company, apparently during 1896 and 1897. EVIDENCES OF ATTACK. The first evidence of attack on living trees is reddish boring dust lodged in the loose bark and moss on the trunk and around the base of the tree, or numerous fresh gum spots or pitch tubes mixed with whitish or reddish borings on the bark of the middle or lower portion of the trunk. TThen this is found it will indicate that the beetles are actively at work excavating the galleries in the bark. After this work is completed and the broods of larvae have killed the inner bark the pitch tubes have an old or dried appearance and the boring dust is less evident. By the time the larva? have developed and trans- formed into pupae and adults during September and October the infested trees are indicated by the faded pale-green appearance of the needles on the trees or on the ground, and by the reddish appearance of the tops from which the needles have recently fallen. During the winter and following spring the trees that were attacked later in the preceding summer will present the same evidence of infestation, and in addition a large percentage of the infested trees are usually marked by woodpecker work. The birds discover the broods of beetles and larvae, and in their efforts to get the insects they remove a sufficient amount of the outer loose bark to give the trunks a conspicuously THE GENUS DENDROCTONUS. 123 reddish appearance, so that even when the leaves on an infested tree are perfectly normal and there are no pitch tubes the trees thus marked by the birds can be readily located as infested trees. As a rule, after the middle of June all of the broods of this insect have left the trees from which the leaves have fallen, and certainly those in which the twigs have changed from a reddish to a grayish appearance. With few exceptions this may be depended upon, because the parent beetles must have living bark in which to deposit their eggs, so that the freshly hatched larvae will have the proper conditions for their future development. Therefore it is sel- dom that more than one set of broods develops in the same tree. This can happen only when but one side of the trunk or the upper or lower portion is infested and the remainder is not dead when the broods emerge. In this case the remaining living bark will be attacked and yield another set of broods. EFFECTS ON COMMERCIAL VALUE OF THE WOOD. The wood of the trees killed by this beetle is not materially reduced in value for several years afterwards, except in so far as the sapwood and heartwood is stained and injured by wood-boring insects, decay, iire, etc. FAVORABLE AND UNFAVORABLE CONDITIONS FOR THE BEETLE. Favorable conditions for the multiplication of this insect are found in large areas of virgin forest, where there is a thick stand of old matured timber and where some of the trees have sufTered from injury by storms, landslides, lightning, or other causes. If, under such conditions, the beetle be present in considerable numbers, it may multiply so rapidly that the best timber in the forests over hundreds of square miles may be killed within two or three years, as has been demonstrated by a number of notable outbreaks in Maine. Unfavorable conditions are found in young, vigorous forests from which the old timber has been removed and utilized, and especially in forests which are under a modern system of forest management, with regulations either requiring that the matured timber be utilized or that all injured or dying trees found to be infested with the beetle be felled and barked or floated at the proper time to kill the broods. METHODS OF CONTROL. Whenever it is positively determined that this species is attacking the living spruce in a given locality, or that the bark of living and dying trees contains living parent adults or developed broods, some measures should be adopted without delay for its control. The removal of the infested bark from the trunks of the trees without burning is all that is necessary to kill the immature stages of 124 THE SCOLYTID BEETLES. the insect at any time. If the work be done during the period begin- ning with the middle of October and ending with the middle of May, say at or below an elevation of about 1,800 feet at latitude 45°, the parent adults and developed broods of adults, together with the immature broods, will be killed. The infested parts of the trunks may be barked without felling the trees, or the trees may be felled for this purpose and barked or utilized and the slabs burned, as in each case may be more practicable or desirable. If the timber can not be utilized for several years it will remain sound much longer if barked and left standing than if felled. If, in the case of a moderate attack, the larger clumps or patches of infested trees and the more accessible scattering ones in the worst affected sections of a forest are barked, it should serve to bring the insect under control the first year, but in the case of a very extensive attack this may require several years. * 1/ ' V ■V'. v V /TCvA Fig. 76. — Trees girdled by different methods: a, Hack-girdled; b, girdled to heartwood: c, hack- girdled and peeled; d, hack and belt girdled. (Author's illustration.) It is not necessary that every infested tree should be barked or utilized, but it is important that at least 75 per cent of such trees be either barked or removed in regular logging operations, before the broods have time to emerge. Whenever a large amount of timber is being killed, as in north- western Maine in 1900, the regular logging operations should be con- ducted in the principal infested areas, in order that the infested trees may be cut and floated out of the forest before the broods have time to emerge. The adoption of this method by the Berlin Mills Com- pany in 1901 was evidently very successful in controlling the insect in the region referred to in B ulletin 28 of this office. It may be practicable to bark newly infested trees in August and September, but the principal work of barking, or removal, or utiliza- THE GENUS DENDKOCTONUS. 125 tion in the regular logging operations, should be done between the middle of October and the middle of May. With this insect it may be practicable to utilize trap trees to at- tract the insects away from the healthy timber. For this purpose living trees, the necessary number depending on the extent of infesta- tion, should be girdled to the heartwood during June. (See fig. 76.) If they become infested during the summer they must be barked or removed by the middle of the following May, in order to destroy the broods. BASIS OF INFORMATION. The preceding information on the eastern spruce beetle is based on investigations by the writer in northwestern Maine in May and June, frf / 0 \ / V-L S*=ZZ> fe / ' — .. ; : -\^^ /.,. 7 V- X X I T~ — / —{ '.'•■{> ry^^rS'-. ......J. | xjs-^s '"iM 1 IvV i ill X^_: •«_ 1 k^ | r™r— r^C"^ ° \ vvri h 11 1 0 • • ^ \\r >~x/7 y \ *^3 Fig. 77.— The eastern spruce beetle: Distribution map. (Author's illustration.) 1900, and at Waterville, N. H., in May, 1903; on experiments with girdled trees by Mr. Austin Cary during the summer of 1900, and instructions to the Berlin Mills Company, in cutting infested timber, in 1901, and on investigations by Mr. W. F. Fiske on Grand Island, Michigan, in October, 1906. Additional localities from correspond- ence and other collections are West Stewartstown, N. H., Anticosti, Canada, and Pennsylvania. It is represented in the forest-insect collection of the Bureau of Entomology by more than 300 specimens. BIBLOGRAPHY. Peck, 1876 (under Hylurgus rufipennis), pp. 283-301; Peck, 1879 (under E. rufipen- nis), pp. 32-38; Hough, 1882 (Insect Ravages), pp. 259-263; Lintner, 1885 (under Dendroctonus rufipennis), p. 54; Fletcher, 1887 (under D. rufipennis), pp. 39-40; Pack- 126 THE SCOLYTID BEETLES. ard, 1887 (under B. rufipennis), pp. 176 and 243; Peck, 1890 (under D. rujipennis), pp. 814-815, and 721-722; Harvey, 1898 (under D . rufipennis) , p. 176; Howard and Chitten- den, 1898 (under D. rufipennis), p. 98; Weed and Fiske, 1898 (under D. rufipennis), p. 69; Hopkins, 1899a (under D. rufipennis), p. 293; Cary, 1900 (under D. polygraphus rufipennis), pp. 52-54; Hopkins, 1901a, p. 16; Hopkins, 1901&, pp. 68-69 ; Hopkins, 19026, p. 21; Hopkins, 1902c, p. 22; Hopkins, 19036, pp. 266-270, 281; Hopkins, 1904, p. 26; Hopkins, 1905, pp. 10-11; Felt, 1905, pp. 6, 7; Felt, 1906, pp. 379-385, 782, 796; Hopkins, 1907, pp. 160-161; Hopkins, 1909, pp. 126-130. Xo. Fig. 78.— TheEngelmann spruce beetle (Dcndroctonus engelmanni) : Egg gallery in living bark. A. Normal; B, boring dust removed; a, entrance; b, basal sec- 15. THE EXGELMANN SPRUCE BEETLE. (Dendroctonus engelmanni Hopk. Figs. 78-82.) The Engelmann spruce beetle is a reddish-brown to black barkbeetle, 5 to 7 mm. in length, with body sparsely clothed with long hairs, head broad and convex, prothorax sometimes darker than the ely- tra and with sides of pronotum distinctly narrowed and con- stricted toward the head and the punctures of irregular size and distinctly coarse, the ely- tra with coarse rugosities be- tween rows of indistinct but coarse punctures, and the de- clivity convex and somewhat flattened. It attacks the En- gelmann spruce, and probably other spruces, from central Idaho southward to the moun- tains of southern Xew Mexico, and the white spruce in the Black Hills of South Dakota. tion;c, boring dust packed in gallery; tf, subsequent -The galleries are Similar to or inner gallery; e, ventilating burrow; /, egg nest, with and without eggs; g, freshly hatched larv?e; h, pits in roof of gallery. (Author's illustration. ) those of the eastern spruce beetle. SEASONAL HISTORY OVERWINTERING STAGES. The broods of this beetle pass the winter in all stages of larva? and as adults in the inner bark of trees attacked by the parent beetles during the preceding summer. THE GENUS DENDROCTONUS. 127 ACTIVITY OF OVERWINTERED BROODS. The adults begin to emerge from the bark and fly during May or June. They settle on felled or standing injured or on healthy trees and enter the living bark to deposit eggs (see fig. 78), which soon hatch into larvae. The broods of larvae feed in the inner bark and destroy that portion of it intervening between the egg galleries, and thus completely girdle and cause the death of the trees which were healthy when attacked. The medium to larger matured trees are the ones commonly selected by the beetle, and it is capable of killing all such timber within a forest. In the Black Hills of South Dakota, at an altitude of about 5,000 feet, Mr. Webb found an adult flying on June 10. On July 30 adults were excavating galleries and depositing eggs, which hatched and had developed into nearly fullgrown larvae on October 14. It would appear, therefore, that the adults of this species come out a little earlier than those of the eastern spruce beetle. ECONOMIC FEATURES. This species, like the eastern spruce beetle, attacks only the larger or mature trees. It is evidently the most important enemy of the Rocky Mountain spruces, and from time to time has caused wide- spread destruction. In October, 1905, the writer found evidence of its destructive work (see figs. 79, 80) in the Pike National Forest, caused many years ago. At the time the observations were made the indica- tions were that the vast destruction of spruce in this reserve here- tofore attributed to fire was primarily caused by this beetle. This was particularly evident on the southern slopes of Pikes Peak, at an altitude of about 10,000 feet, where nearly all of the timber had been killed some fifty years ago. In the fragmentary patches of living timber, old felled trunks of a primitive matured forest of Engelmann spruce were found thickly covering the ground. On the weather-beaten surface of these logs the characteristic markings of the galleries of this beetle were so common as to leave little doubt that the trees had been killed during a destructive invasion by it — indeed, very conclusive evidence of this was found in the presence of dried resin in the egg-gallery grooves and on the surface of the wood, which would not be found there if the trees had been attacked after they were dying from other causes. This additional evidence, together with the known devastating work of this class of insects, makes it clear to the writer that there has been a most intimate interrelation of destructive barkbeetles and forest fires in the denudation of the vast areas of once heavily forested lands in the Rocky Mountain region, and that in very many 128 THE SCOLYTID BEETLES. cases the insects have first killed the timber, and the fire has then followed (see fig. 81), leaving the charred trunks and logs as apparent proof that the fire alone was responsible. In August, 1905, Supervisor A. W. Jensen, of the Manti National Forest, Utah, reported much destructive work by a beetle which proved to be this species. He stated that in some sections 20 per cent was then attacked or killed, including both the Engelmann spruce and the blue spruce. In August, 1906, Mr. Harry Gibler reported that all of the matured Engelmann spruce of the White River National Forest, in Colorado, was more or less affected by a beetle which the writer identified as this species. In response to a request for more detailed informa- FiG. 79. — Engelmann spruce evidently killed by Engelmann spruce beetle about 1853-6; pitch-marked galleries common on trunk. Pike National Forest, at elevation of about 10,000 feet. (Original.) tion, Mr. Gibler, in a letter dated November 13, 1906, wrote as follows : There is no portion of the reserve on which they are especially active, but are more or less over the entire area. In some places as much as 90 per cent of the mature timber is already dead and in some localities as little as 2 per cent seems to be affected, and in this connection I would state that so far the oldest trees, and that which is classed as strictly mature timber, have been affected. In the Twentieth Annual Report of the United States Geological Survey, p. 137, Mr. G. B. Sudworth states: There is a considerable quantity of dead standing spruce mingled with the green timber. It extends in an interrupted irregular narrow belt from the region of Deep Lake and Carbonate westward to the headwaters of East Elk Creek. The dead tim- THE GENUS DENDKOCTONUS. 129 "ber amounts to from 10 to 25 per cent of the total stand and includes nearly, or quite, all the largest and oldest trees. They bear evidence of having died about twenty to twenty-five years ago. Mr. W. D. Edmonston inspected this timber on September 23-24, 1907, and reported to the writer as follows: I don't know where Mr. Sud worth observed the old and dead spruce; but I was with Supervisor Blair when he was estimating for a sale of Engelmann and Alpine iir (September 23, 24, 1907) in Bear Park, near Dale's sawmill, 12 miles northeast of New Castle, and we found all through this body of timber that the dead Engelmann, all over 15 inches in diameter, amounted to 25 per cent. I examined this dead timber most carefully. I spent the entire day examining the trees, while Mr. Blair and two of his rangers were estimating. I did not find one single Engelmann that had died within the past twenty-five years that had not been beetle-killed, the galleries of the Engelmann spruce beetle showing plainly on the trunk. I pointed out hundreds of Fig. 80.— Engelmann spruce timber evidently killed by Engelmann spruce beetle and subsequently partially burned by fire. Pike National Forest, at elevation of about 10,000 feet. (Original.) such trees to Mr. Blair and the rangers. But I failed to find any new work. This timber must have been killed about twenty years ago, if not longer. Old snags, stand- ing and down, all showed plainly the yellow-stained galleries, just like those you pointed out to me the day we were at Clyde, on the road to Seven Lakes, in the Pikes Peak, and just the same as that on the specimen I sent you from near Crested Butte, Gunnison National Forest. On January 10, 1908, Mr. W. D. Edmonston reported that the large stands of Engelmann spruce in the White River National Forest showed an average of 20 per cent beetle-killed throughout. In March, 1907, Mr. Frank J. Phillips, forest assistant, of the Forest Service, in a report on conditions in the Lincoln National Forest, New Mexico, refers to a forest fire of doubtful date, 1892 to 1895, which it is claimed killed and weakened portions of the spruce stand 89535— Bull. 83, pt. 1—09 10 130 THE SCOLYTID BEETLES. aggregating approximately 1,200 acres, although it is probable that the insect was present before the fire occurred. He states as follows : Two or three years after trie fire serious work of the insect was first made apparent, and local observers state that the beetle work has steadily increased until the entire spruce stand is threatened with insect destruction. In his 1904 report Mr. F. G. Plum- mer stated, "Notwithstanding the fact that the summits of the Sierra Blanca afford apparently ideal conditions for the growth of the spruce, about 20 per cent of the standing trees are dead or dying. This gives the forest the appearance of having been scorched by a fire not severe enough to utterly destroy it. For this no cause was found. *■ * * Fig. 81.— Average-sized Engelmann spruce killed by fire and the Engelmann spruce beetle. National Forest, at elevation of 10,150 feet. (Original.) Lincoln The insect work occurs at an elevation above 9,000 feet and will probably extend to the altitudinal limit of the spruce in case it has not already done so. It was found in trees varying from 6 to 20 inches, which had not been subject to other injury. Approximately 1,000 acres of the headwaters of the South Fork of the Kio Bonito have been completely killed by the combined effect of fire and insects, and other similar areas exist in the reserve. Mr. F. G. Plummer, of the Forest Service, in a report entitled "Forest conditions in the Lincoln Xational Forest, Xew Mexico 7'a estimates a total stand of 29,027,000 feet, board measure, on 13,142 acres. Of this, 1,480 acres, or about 9 per cent, has been burned. a Professional Paper No. 33, series H. Forestry. 11, U. S. Geological Survey. THE GENUS DENDROCTONUS. 131 Mr. W. F. Fiske, of this Bureau, who was sent to investigate the conditions as to insect ravages in the White Mountains of the Lincoln National Forest, reported that during his investigations in May, 1907, he found that at least 95 per cent of all of the Engelmann spruce out- side of the burned areas was beetle-killed, but that practically all of this was rather old work and that there was very little evidence of the beetles' presence at that time. Mr. J. L. Webb, of this Bureau, visited the same area in September and estimated that fire had killed about 15 per cent of the total stand of spruce, and that the beetle has killed about 90 per cent of the remainder. METHODS OF CONTROL. The methods of controlling this beetle are essentially the same as for the eastern spruce beetle. Fig. 82. — The Engelmann spruce beetle: Distribution map. (Author's illustration.) BASIS OF INFORMATION. Information concerning this barkbeetle is based on investigations by the writer at Boulder, Colo., August, 1901; at Black Hills, S. Dak., September, 1901, and August, 1902, and in the Pike National Forest, Colo., October, 1905; by Mr. J. L. Webb, at Collins, Idaho, September, 1900; in the Black Hills, S. Dak., June and October, 1902, and August, 1906; in the Rincon Mountains, Ariz., and in the Capi- tan Mountains and at Cloudcroft, N. Mex., from May to Septem- ber, 1907; by Mr. W. F. Fiske, in the Capitan Mountains, N. Mex., May, 1907; by Mr. W. D. Edmonston, in the Ouray National Forest, at Craig, Steamboat Springs, and Hahns Peak, in the White River 132 THE SCOLYTID BEETLES. National Forest, and in the Holy Cross National Forest, Colo., and at Encampment, Wyo., in 1907. Additional localities through cor- respondence and from collections are: Ephraim and Alta, Utah; Meeker, Silver Plume, Argentine, Glenwood Springs, and Leadville, Colo.; Capitan, Lincoln National Forest, and Las Vegas, N. Mex.; Calgary, Alberta Province, and Glacier, British Columbia. It is represented in the forest-insect collection of the Bureau of Entomology by more than 200 specimens. BIBLIOGRAPHY. Packard, 1877 (under Dendroctonus obesus), p. 803; Hopkins, 1906a (under D. piceaperda), pp. 4-5; Hopkins, 1907 (under "The Engelmann spruce beetle"), pp. 161-162; Hopkins. 1909, pp. 130-133. Xo. 16. THE ALASKA SPRUCE BEETLE. (Dendroctonus borealis Hopk. Figs. 83, 84.) The Alaska spruce beetle resem- bles closely in general characters the eastern spruce beetle, but is smaller, and is distinguished by the coarser punctures of the pronotum being more regular in size. (See fig. 83.) This species is represented in the collections by but four speci- mens, two in the United States Na- tional Museum collection, labeled "Alaska/' and two in the forest- insect collection of the Bureau of Entomology, collected by Mr. W. H. Osgood from white spruce at Eagle, Alaska, in August, 1903. Nothing further is known about this species, but it will probably be found that its habits and life history are similar to those of Xos. 14 and' 15. . Fig. 83.— The Alaska spruce beetle (Dendroctonus borealis): Adult. Greatly enlarged. (Author's illustration.) BIBLIOGRAPHY. Hopkins, 1909, pp. 133-135. No. 17. THE SITKA SPRUCE BEETLE. (Dendroctoiius obesus Mann. Figs. 85, 86.) The Sitka spruce beetle is a large, stout, black, cylindrical bark- beetle 6 to 7 mm. in length, with broad convex head, the sides of pronotum narrowed and constricted toward the head, and surface THE GENUS DENDROCTONUS. 133 punctured with irregular large and small punctures, the elytra with moderately coarse rugosities between moderately distinct rows of punctures, and the declivity not strongly convex and nearly smooth, shining in the male, more dull and roughened in the female. The entire body is sparsely clothed with long hairs. (See fig. 85.) It attacks the living bark on the trunks of living, dying, and newly felled trees, stumps, and large branches of Sitka spruce, from New- port, Oregon, northward along the coast to Alaska, probably following the distribution of the tree in which it lives. The general character of attack and of egg and larval mines is practically the same as de- scribed under D. piceaperda, except that the larval mines are perhaps more generally connected toward the egg gallery and that the pupal cases are sometimes grooved in the wood, while others are concealed in the outer portion of the inner bark. Fig. 84.— The Alaska spruce beetle: Distribution map. (Author's illustration.) SEASONAL HISTORY. OVERWINTERING STAGES. The winter is passed principally as adults and matured larvae in the inner bark on trees, logs, and stumps where they developed the preceding summer. ACTIVITY OF OVERWINTERED BROODS. Activity of the overwintered broods begins in April. The adults begin to emerge about the middle of April, and continue to come out as the broods of overwintered larvae develop, probably until the 1st of July, but the principal period of emergence is during May and June. 134 THE SCOLYTID BEETLES. GENERATION. The adults begin to attack the trees, excavate galleries, and deposit eggs early in May, and continue to do so through June, probably until August, though the principal period is in May and June. Fresh attacks and eggs are also found in September, either by adults of overwintered broods or those developed from eggs deposited early in the spring. The larva? begin to hatch in May, and probably continue hatching until in August, but the principal period is in June and July. The principal period of larval develop- ment is during June, July, aud August. The larva3 begin trans- forming to pupae toward the last of July, and continue transforming probably imtil winter, but the princi- pal period is in August and September. The pupae begin to transform to adults probably during the second week in August, and continue transforming un- til winter. The principal period of transformation to adults is during the month of September. The period re- quired for the development from eggs to adults is about three months. The more advanced broods of the generation complete their development by the last part of August and first part of September, while the later ones evidently pass the winter as mature larvae and immature adults, to com- plete their development the following spring. There is, therefore, one com- plete generation during the year. The fact that eggs and young larva? are common in September indicates that some of the broods of the first generation may emerge in the fall and deposit eggs from which there is a partial second generation, but it is not improbable that some of the parent beetles of the overwintered broods may leave the trees after they have completed the first set of galleries, and excavate galleries in the same or other trees. If there is a partial second generation the brood passes the winter in the larval stage, possibly together with the parent beetles. HABITS. This species appears to prefer to attack the living bark on the trunks and stumps of felled trees and on the trunks of those still standing but weakened and injured. Apparently it will not attack Fig. S5.— The Sitka spruce beetle (Den- droctonus obesus): Adult. Greatly en- larged. ( Author's illustration.) THE GENUS DENDROCTONUS. 135 healthy trees when there are plenty of felled and injured ones for it to infest. So far as observed it attacks only the Sitka spruce, but it is probable that it will be found in the Engelmann and white spruces, if they grow in the vicinity of the Sitka spruce. The gallery is very much the same as those of the eastern spruce beetle and the Engelmann spruce beetle, except that the larval mines appear to be even more generally connected toward the egg gallery. The larvae and pupae are either exposed or hidden in the inner bark, and the pupal cells are sometimes grooved in the surface of the wood. Sufficient observations have been made on the flight of this species to indicate that it flies during the day, and even in bright sunshine. Fig. 86.— The Sitka spruce beetle: Distribution map. (Author's illustration.) ECONOMIC FEATURES. So far as observed, this species has not been found attacking healthy trees in sufficient numbers to cause their death, but it is not improbable that under specially favorable conditions for the increase of its broods the older living timber might be attacked and killed as it is by the eastern spruce beetle. If so, the evidence of attack would be similar to that described under Nos. 14 and 15. METHODS OF CONTROL. If this barkbeetle should be found killing trees, the method of con- trol would be similar to that recommended under the eastern spruce beetle, except that summer operations of barking or utilizing the 136 THE SCOLYTID BEETLES. infested trees during June, July, and August would be less objection- able. As a rule, however, winter operations would be preferable, the work to be completed before the 1st of April. BASIS OF INFORMATION. Information regarding this species is based on investigations by the writer at Newport, Oreg., April, 1899, and at Hoquiam, Wash., May, 1903; by Mr. H. E. Burke at Aberdeen and Hoquiam, Wash., April to June, 1903, and August, 1903, at Hoquiam and Aberdeen, Wash., May to September, 1904, and at Hoquiam May and June, 1905. Additional localities from correspondence and other collec- tions are Queen Charlotte Islands and Vancouver, B. C. It is rep- resented in the forest-insect collection of the Bureau of Ento- mology by more than 120 specimens. BIBLIOGRAPHY. Hopkins, ,18996 (under Dendroctonus similis and sp. near D. rufipennis), pp. 15, 21; Hopkins, 1902c, p. 22; Hopkins, 1903a, p. 60; Hopkins, 1904 (under D. obesus), p. 19; Hopkins, 1909, pp. 135-138. No. 18. THE REDWINGED PINE BEETLE. (Dendroctonus rufipennis Kirby. Figs. 87, A, 88.) The redwinged pine beetle (fig. 87, A) is a stout, cylindrical bark- beetle, with reddish elytra and dark-brown or black prothorax, 5 to Fig. 87.— A, The redwinged pine beetle {Dendroctonus rujipennvs), adult, greatly enlarged; B, the lodgepole pine beetle (Dendroctonus viurrayanss) , larva, less enlarged. (Author's illustrations.) THE GENUS DENDROCTONUS. 137 7.5 mm. in length, with the head broad and convex; the prothorax slightly narrower than elytra, its sides narrowed and slightly con- stricted toward the head, the surface even and shining, with coarse and small punctures intermixed; the elytra with moderately coarse rugosities between rows of moderately coarse and but slightly im- pressed rows of punctures, and the declivity smooth and shining in the female and less shining and more rugose in the male. It attacks felled white pine in northwestern Michigan. The primary or egg gallery is evidently of the same character as those of the spruce beetles, but the larval mines are probably like those of the European spruce beetle and the black and red turpentine beetles of this coun- try. The larvae resemble those of the eastern spruce beetle in the Fig. -The redwinged pine beetle: Distribution map. (Author's illustration.) dorsal plates on the last two abdominal segments, but are distin- guished by a row of brown spots (spiracles) on each side of the body, as in figure 87, B. SEASONAL HISTORY. This species evidently passes the winter in the adult and larval stages. Fully developed broods and larvae were found by Mr. W. F. Fiske, October 20, at Grand Island, Mich. Nothing further is known of the life history, but it is probable that it will not differ materially from that of the eastern spruce beetle. HABITS. Mr. Fiske found the developed broods under the bark on the underside of the trunk of a storm-felled white pine some distance from the base. Nothing further is known of the habits of this 138 THE SCOLYTID BEETLES. species, although it was one of the first species of the genus to be described from North America. BASIS OF INFORMATION. Information about this species is based on investigations by Mr. W. F. Fiske, on Grand Island, Mich., October, 1906. An additional locality from the collection of the United States National Museum is Whitefish Point, Mich. The species is represented in the forest- insect collection of the Bureau of Entomology by 14 specimens. BIBLIOGRAPHY. Hopkins, 1901a, p. 16; Hopkins, 19026, p. 10, footnote; Hopkins, 1909, pp. 138-140. No. 19. THE LODGEPOLE PINE BEETLE. (Dendroctonus murrayanx Hopk. Figs. 87, B, 89.) The lodgepole pine beetle is a stout, cylindrical barkbeetle, 5.4 to 6.5 mm. in length, with reddish elytra and dark-brown or black pro- thorax; the head broad, convex; the pronotum slightly narrower than the elytra, its sides narrowed and constricted toward the head, the punctures coarser and less uneven sizes than in No. 18, and the elytra with rows of coarse, shallow punctures. It attacks lodgepole pine in southern Wyoming and occurs northward to Alberta, B. C. The egg gallery is like that of the eastern spruce beetle, but the larval mines are more like those of the European spruce beetle. Adults were found excavating galleries and depositing eggs July 31, at Saratoga, Wyo. (Medicine Bow National Forest), in young living lodgepole pine, by Mr. Jeremiah Rebmann, of the Forest Service. On October 12 parent adults and half-grown larvae were found in the same tree. HABITS. According to Mr. Rebmann' s observations, the species attacks living trees toward the base, excavates galleries as much as 18 inches in length, with large pitch tubes at the entrance, and deposits the eggs along one side, partitioned off with boring dust. The same trees were thickly infested with the Oregon Tomicus ; therefore it was not determined whether the Dendroctonus or the Tomicus made the first attack. The fact, however, that there were large pitch tubes indi- cated that the primary attack was made by this species, although many other trees were found infested and killed by the mountain pine beetle. The work of the lodgepole pine beetle was observed in but a few trees. Fragmentary specimens of a beetle identified as this species were received in August, 1905, through the Forest Service, from Mr. THE GENUS DENDROCTONUS. 139 W. E. Jackson, with the statement that the beetle was doing consid- erable damage in the Big Horn National Forest, Wyo. Nothing further is known of the habits of this species. BASIS OF INFORMATION. Information about this species is based on specimens and notes received from Forest Assistant Jeremiah Rebmann, of the Forest Service, July, August, and October, 1905, collected in the Medicine Bow National Forest, Wyo., and through the Forest Service from W. E. Jackson, Big Horn National Forest, Wyo.; on investigations by Mr. W. D. Edmonston, in the Pike National Forest (Jefferson), Colo., December, 1906; on specimens received through the Forest Service from the Cheyenne National Forest, September, 1908. Addi- Fig. 89. — The lodgepole pine beetle: Distribution map. (Author's illustration.) tional localities from correspondence and other collections are, Saratoga, Yellowstone National Park, and Homestake, Wyo. It is represented in the forest-insect collection of the Bureau of Ento- mology by more than 100 specimens. BIBLIOGRAPHY. Hopkins, 1909, pp. 140-142. No. 20. THE ALLEGHENY SPRUCE BEETLE. (Dendroctonus punctatus Lee. Figs. 90, 91.) The Allegheny spruce beetle is a stout, brownish, cylindrical bark- beetle, 6.5 mm. in length, resembling D. piceaperda, but larger, with distinctly longer elytra in proportion to the thorax; head broad, 140 THE SCOLYTID BEETLES. shining; thorax slightly narrower than elytra, with sides distinctly narrowed toward the head, the surface with coarse and fine punc- tures; elytra elongate, with coarse rugosities between rows of indis- tinct coarse punctures, the punc- tures on the sides of the elytra very coarse; the declivity with rows of coarse, distinct punctures, and the body sparsely clothed with long hairs. (See fig. 90.) BASIS OF INFORMATION". One specimen of this species was taken by the writer in the higher mountains of Randolph County, W. Ya., May 21, 1893, from \ freshly excavated gallery in the bark of the stump of a red spruce tree felled during the previous winter. This appears to be all that is known of its habits. It is represented in the Le Conte collection by two specimens from New York, from which descriptions were made in 1868, and by one the collection of the Academy of Fig. 90. — The Allegheny spruce beetle (Dendroc- tonus punctatus): Adult. Greatly enlarged. (Author's illustration.) specimen from Pennsylvania in Fig. 91. — The Allegheny spruce beetle: Distribution map. (Author's illustration.) Natural Sciences, Philadelphia, Pa. Therefore, so far as known, its THE GENUS DENDROCTONUS. 141 distribution is confined to the region of the mountains of West Vir- ginia and northward to northern New York. This species comes nearer to the European spruce beetle than it does to any of the other species, and therefore will probably have similar seasonal history and habits. BIBLIOGRAPHY. Hopkins, 1899a, p. 447; Hopkins, 1909, pp. 142-143. No. 21. THE EUROPEAN SPRUCE BEETLE. (Dendroctonus micans Kug. Figs. 92-94.) The European spruce beetle is a large, stout, reddish-brown, cylin- drical barkbeetle, 7 to 8 mm. in length, with broad, convex head; short prothorax, with sides of pronotum distinctly narrowed and constricted toward head; elytra somewhat shining, with moder- ately coarse rugosities between rows of rather distinct punctures, and the declivity smooth and more shiny in the males than in the females. (See fig. 92.) According to European writers, it attacks the living bark, usually at the base of injured, dying, and living trees and stumps of felled spruce, pine, fir, and larch, from central to northern Europe and in Denmark, Kussia, and eastern Siberia. HABITS AND SEASONAL HISTORY. It is said that the broods pass the winter in the mines in the bark as parent adults, young adults, and all stages of larvae. The young adults emerge in June and excavate long, irregular egg galleries (fig. 93), usually in the bark at the base of stumps and trees, some- times extending into the roots, but sometimes at various points on the trunk, even to and among the branches. The female deposits from one hundred to one hundred and fifty eggs in groups of from thirty to fifty, and the larvse proceed in a body to excavate broad brood chambers (fig. 93), very much in the same manner as with the black and red turpentine beetles. The broods hatching from eggs deposited in May and June by the overwintered adults develop into pupae and adults by September, or later, but remain in the brood galleries until the next spring. The broods developing from overwintered young larvae transform to pupae and adults in June and July, emerge and deposit eggs in July and August, or later, and pass the winter in different stages, as young to matured larvae. 142 THE SCOLYTID BEETLES. ECONOMIC FEATURES. , It is said that this species prefers to attack the bark on the base of the trunks and roots of sound or healthy trees, and that the connect- ing of the broad larval chambers from the same egg gallery or from several galleries has the effect of girdling the tree, either causing its death or a weakened condition which attracts other barkbeetles to complete the destruction. Young as well as old trees are attacked, but, while this species will breed in standing injured or weakened trees, it rarely breeds in felled ones. It apparently prefers the spruces, but will, according to dif- ferent authors, attack pine, fir, and larch. The evidences of attack are masses of gum or resin and so- called pitch tubes, mixed with reddish boring dust. METHODS OF CONTROL. Removing the bark from the in- fested trunk and roots, or scorch- ing it if not removed, is recom- mended to kill the broods. Coat- ing the trunks of the trees with a preparation of tobacco water, Spanish blood, lime, fresh cow dung, etc., is recommended as a preventive. After the above was written the writer received a paper on the genus Dendroctonus from Dr. G. Severin (1908), director of the Royal Museum of Natural History of Belgium. A large series of specimens of the beetle and its work was also received from Doctor Severin, which was of special value and interest. Doctor Severin's paper covers the more impor- tant historic and economic information on the species recorded in European literature to 1908. Some of the information in the paper that is of special interest in connection with a discussion of all of the species is summarized as follows: Fig. 92. — The European spruce beetle (Den- droctonus micans): Adult. Greatly enlarged. ( Author's illustration.) Information from Paper on the Genus Dendroctonus, (1908,, pp. 1-20). by Dr. G. Severin Dendroctonus micans alone, of all the hylesinids, and perhaps of all the scolytids, appears to love the resin and to live there with ease. It neglects the weak trees and is found principally upon trees full of vigor, of an age of 30 years and more, where it THE GENUS DENDROCTONUS. 143 lives in the middle of pockets full of resin. During the larval period micans conducts itself differently from other Belgian hylesinids in that each larva does not make a separate gallery, but all work together, making one common wide gallery. The egg- laying extends sometimes over several months. This results in a parallel develop- ment of larvae, pupae, and adults, which are to be found thus during the greater part of the year. The excavation of the gallery begins the last of May or the first of June. The attack of the insect, which traverses the bark to reach the sap wood, causes each time an abundant flowing of resin mixed with sawdust and excrement, which gives it a brownish color, sometimes violaceous. This resin often forms nipplelike blocks, sometimes 30 mm. high by 25 mm. in diameter, which dry and harden in the air and finish by crumbling. The particles fall at the foot of the tree, among the needles Fig. 93.— The European spruce beetle. Egg galleries and larval chamber: A, Basal sections of egg galleries; B, advanced stage of work; a, entrance burrow; b, excavated July 8-16; c, excavated July 8-29; d, eight days old; e, three weeks old;/, basal section; g, boring dust; h, subsequent or inner gallery ("mother gallery"); j, egg nest with eggs scattered about in boring dust; k, social chamber excavated by larvae; I, boring dust and resin; m, larvae at work. (Adapted from Pauly, Forstlich-naturwissenschaftliche Zeitschrift, I Jahrgang, figs. 3 and 4.) forming the ground cover, often being in a very considerable number, resembling the dried lumps of mortar at the foot of a freshly constructed wall, following the excellent comparison of Altum. The egg gallery is vertical, frequently curved and somewhat irregular, sometimes doubly inflected, having 12 to 20 cm. of length. The female here deposits from 20 to 25 eggs several times. Following this she quits this place, to commence upon another point of the same tree or upon neighboring trees, even to the deposition of from 15fr to 200 eggs. Sometimes she is found dead in a final gallery having deposited but a few eggs, the rest of her provision. The egg laying is done slowly after this preparatory work. It is therefore easily understood that a female which has deposited her first eggs about the month of June 144 THE SCOLYTID BEETLES. sometimes goes to the month of September before having finished the operation. It transpires, perhaps, that the mother hibernates and finishes the evacuation of her eggs at the commencement of the following year. The larvae eat very close together, growing equally in size and age and making a common cavity underneath the bark. These larvae are white and resemble those of Pissodes or the young larvae of Hylobius. In order to go through the pupal stage, they return to the large space which they left behind them and which is filled with excrement agglutinated by resin. It is there that they construct their pupal cases, unless, departing from their common cavity, they eat out isolated galleries at the end of which the pupal cases are formed. Here they hibernate also and the perfect adults here find their chamber of hibernation, although they approach a little nearer the place of entrance. It is apparent from the preceding that an egg laying extending often over several months produces evolutionary cycles very different from each other as long as it lasts. If the larvae which pass over the winter can find a sufficient quantity of heat for their complete evolution they go on to the pupal and adult stages. Others will be found later which will not be able to terminate their larval stage before the weather turns cold again and will be obliged to hibernate in their cells made in the middle of the dried excrement. Between these two extreme cases one finds intermediate stages, possibly, for example, some in the pupal state. A hatching taking place toward the middle of this favorable period would not per- mit them, therefore, to attain their growth before winter. In winter the adult secretes itself most often in wounds on the tree, where the larval state has been passed, or else it eats out small galleries between the roots and even under the bark, underneath the level of the ground. This giant hylesinid lives almost entirely in spruce. The trees on the outskirts of a planting, south and east, so that they are more exposed to the rays of the sun, are the most menaced. As I have already said, the spruces from 25 to 50 years old are the most often attacked, but the old plantings from 60 years and more are not immune. Micans should be counted among the insects very destructive to spruce. If the first attack does not kill the tree, it does not resist the attacks of the following genera- tion which girdle the trunk by wounds and take all the natural adhesion between the bark and sapwood away. In this case the upper part of the trunk dies rapidly. When attack is made upon the roots the tree continues to live, at least while there are not a great many wounds upon several roots. This insect was first introduced in forest entomology by Von Sierstorpf in 1794 under the name of Bostrichus ligniperda, but neither he nor Ratzeburg much later, and who did not repeat the statements made by Saxesen, believed that this insect was a serious enemy. Stein, in 1852, did not believe it injurious, but two years later, in 1854, he had to modify his opinion, after great destructions of trees in the forests of Neudorf in Saxony, where micans attacked plantings from 40 to 50 years old, which had to be cut and sold on account of the attacks of insects. Before 1858 the insect was almost unknown to Austrian entomologists. At that date Kollar speaks of a serious attack upon the spruces 100 years old in the Imperial Park of Laxenburg near Vienna, where micans had attacked in the beginning only some old trees which resisted for several years. At the reunion of the Foresters' Society of Harz in 1867 communications upon the presence of D. micans came in from all sides. They had found it in Harz, in Thurin- gerwald, in Anhalt, and in the plains in the forestry district of Marienthal, near Bruns- wick, without meanwhile considering its presence a great nuisance. In 1872 at the same assemblage Gebelers speaks of an attack at Thale in Harz, where D. micans had destroyed 10 hectares a of spruces mixed with sylvestral pines, "English equivalent, 24.71 acres. THE GENUS DENDROCTONUS. 145 all of them about 35 years old. Gliick in 1876 cites a very strong attack in Rheinfalz near Coblenz. Since then the insect appeared everywhere and complaints arise every year in German forest literature. We know that the insect in its continual extension toward the west, after having seriously ravaged the plantings of Eiffel and of German Herzogenwald, has finished by reaching our frontier, and that it was discovered for the first time in Belgium in 1896 in Herzogenwald. It is quite clear that the preparation of trap trees in the sense that one understands them for the other scolytids can accomplish nothing. The remedial measures in actual use are as follows: When the laborer going to his work in Herzogenwald, or the forest officer on his circuit, notices any of the character- istic signs of the attack of D. micans he does not fail to make known at once his dis- covery. In order to easily find the tree again he should attach around the trunk a belt of ferns or grass. At certain periods, several times during the dangerous months, later not so often, a worker, armed with a knife and a pruning knife, sometimes with a light ladder and a pail of coal tar or tar, makes the inspection of the contaminated Fig. 9J.— The European spruce beetle: Distribution map. (Author's illustration. After having encircled the tree with a special apron of twist, he raises the bark at the place of attack, cleans out the wound made by the larvse, and re-covers it with the liquid preservative. The dried particles taken out are given to the fire and destroyed to the last particle, except during the months of summer, when the parasite, Fimpla terebrans, is to be found. When these are found it is necessary to examine the debris upon a sheet or cloth. In order to clean out the wounds found upon the roots at their branching, a tool in the form of a recurved spade is used. The expense resulting from such surveillance and the work of cleaning is net excess- ive when the attack is in its infancy and the trees attacked are not yet numerous. Rarely it happens that the tree must be cut down. It is not the same when the insect has been able to install itself in a planting for several years and to form serious breeding places. In order to avoid, then, making clearings in the middle of dense plantings, it is necessary to proceed with great pru- dence, to clear out with circumspection, and to sometimes clean the trees high and low when this is still possible. It is estimated that trees which are not attacked for more than two- thirds of the circumference of the trunk can in this extreme case be cleaned out and re-covered carefully with coal tar or tar. 89535— Bull. 83, pt, 1—00 11 146 THE SCOLYTID BEETLES. It is evident that the price of cleaning becomes then very high; but we are com- pensated by preserving precious trees to continue the existence of the planting. In conclusion, we counsel, therefore, repeated visits during the summer months in the forests where the presence of D. micans has already been determined and in those where it may be expected; then, visits less frequent during the months of spring and winter. We counsel, also, the assembling of all the official personnel of the forest service as soon as the presence of the insect is found and the giving of instruction as to the characteristic appearances attended by the insect attack. If necessary, a bounty might be paid. After examining the trees designated, the foresters will decide whether it is best to cut down the trees or clean them. In this manner it will be everywhere as in Herzogenwald, where a rigorous sur- veillance, but not at all expensive, has rendered the existence of the insect almost, impossible. SPECIMENS. This species is represented in the forest-insect collection of the Bureau of Entomology by 90 specimens, including adults, larvae, and work. BIBLIOGRAPHY. Ratzeburg, 1839 (under Hylesinus (Dendroctonus) micans), p. 217; Stein, 1854, (under Hylesinus micans), pp. 277-279; Kollar, 1858, pp. 23-28; Eichhoff, 1881, pp. 125-128; Altum, 1881, pp. 262-266; Judeich u. Nitsche, 1889, pp. 458-462; Menegaux et Cochon, 1897, pp. 206-209; Severin, 1902, pp. 72-81, 145-152; Weber, 1902, p. 108; Brichet et Severin, 1903, pp. 244-258; Baudisch, 1903, pp. 151-152; Quairiere, 1904-5, torn 11, pp. 626-628, torn 12, pp. 183-186; Quievy, 1905, pp. 334-335; Nusslin, 1905, pp. 175-178; Severin, 1908, pp. 1-20; Hopkins, 1909, pp. 143-146. No. 22. THE BLACK TURPENTINE BEETLE. (Dendroctonus terebrans Oliv. Figs. 95, 96.) The black turpentine beetle is a large, stout, dark-brown or black, cylindrical barkbeetle, 5 to 8 mm. in length, with broad prothorax, coarsely punctured pronotum, the sides slightly narrowed toward the head, but not strongly constricted; the elytra with coarse, trans- verse to oblique rugosities between distinct to obscure rows of punc- tures; the declivity convex, with moderately deep grooves, the intervening spaces slightly convex and roughened, and the entire body sparsely clothed with long hairs. (See fig. 95.) It attacks the living bark, usually at the base of injured, dying, or healthy trees, or the stumps of felled pine and spruce, from Long Island, N. Y., south- ward to Florida and westward to Texas and. West Virginia, but it is more common in the South Atlantic and Gulf States. The parent beetles excavate broad, somewhat irregular, winding, longitudinal or sometimes transverse egg galleries through the inner bark and groove the surface of the wood. The eggs are placed in groups or masses at intervals along the sides of the galleries. The stout, yel- lowish-white, cylindrical larvae, with reddish heads and stout spines THE GENUS DENDROCTONUS. 147 on the dorsal plates of the last abdominal segments, do not make separate larval mines, but all feed together and eat out cavities in the inner bark from a few inches square to several feet square. They transform to pupae and adults in separate or closely- joined cells in the inner bark or inner portion of the outer bark, but a few of the larvae sometimes excavate independent mines beyond the social chamber for the purpose of pupating. The broods work independently of other species and occupy and separate the bark around the base of trees and stumps, often extending their work for a foot or more under the bark onto the roots beneath the surface. The broad lar- val chambers are often filled with semiliquid resin without injury to the occupants. The attack on living trees and on stumps of those recently felled is indicated by large masses of pitch and pitch tubes, mixed with red- dish borings. SEASONAL HISTORY. Northern Section. overwintering stages. The winter is passed in and beneath the bark of trees and stumps attacked the preceding spring and summer, as parent adults, larvae, and developed broods. The larvae, as a rule, occupy the bark on the roots beneath the sur- face of the ground. ACTIVITY OP OVERWINTERED BROODS. The overwintered parent adults begin to extend their galleries or fig. 95.— The black turpentine beetle (Dew- emerge and excavate new Ones earlv droctonus terebrans): Adult. Greatly en- 0 . . ., , larged. (Author's illustration.) m March or in April, depending on the locality, and probably continue active until June or later. The overwintered broods of developed adults begin to emerge from the bark and fly early in March, at Try on, N. C, or in April or May farther north and at high altitudes. Their principal work of exca- vating egg galleries is carried on during April and May, but is continued until hibernation begins in the fall. The overwintered broods of large larvae evidently complete their development and emerge in May and June, while some of the young larvae may not complete their development and emerge until August 148 THE SCOLYTID BEETLES. or later. Therefore there is a succession of emerging adults through- out the greater part of the warm season, and it is not improbable that some of them pass the second winter as matured adults. GENERATION. The broods from eggs of overwintered parent adults evidently de- velop into adults, some of which emerge before hibernation begins in the fall, but it is probable that most of them pass the winter as matured adults. The overwintered broods of adults begin to deposit eggs in March and April, and continue to do so as successive broods appear until activity ceases in the fall. The eggs begin to hatch in March and April, the process continuing during April and May and until July or later. The principal active or feeding stage of the larvae is during the period from May to July, but this stage may occur in any month of the year. The more advanced broods from eggs deposited in March evidently transform to pupae and adults in July or August, but it appears that the principal period of transfor- mation is in the fall, while the broods from eggs deposited in the sum- mer do not transform until the following spring. It is probable that some of the adults of the earlier broods may emerge in the fall, but no good evidence has been found that they do so in the northern section of the distribution. There is, however, such a complex overlapping of broods that it has been difficult to arrive at any conclusions regarding the normal period required for the development and emergence of all of the broods of a generation. It is evident, however, that in the northern section there is but one generation annually, and that in some cases it may require two years from the appearance of the earliest broods until all of the latest broods have developed and emerged and that, therefore, individuals of one generation may pass over two winters, first as young larvae, and second as matured adults and larvae, the latter from eggs deposited in the spring by the overwintered parent adults. It may also happen, as is known in some Curculionidse, that some of the adults may live two years or more. Southern Section. In the region east of central North Carolina and south of western North Carolina and eastern Tennessee the seasonal history differs from that in the northern section, mainly in the fact that activity begins earlier in the spring and continues later in the fall, that in its more southern distribution it evidently continues active during the entire year, and that there is one complete generation and a par- tial second, if not two generations, annually, in the most southern localities. THE GENUS DENDRQCTONUS. 149 HABITS. This species prefers to enter the bark at the base of injured and dying trees and the stumps of those newly felled, though it will attack the main trunk of living trees, and if in sufficient numbers may cause their death without the aid of other agencies. Evidences of this have been noted by the writer on Long Island, N. Y., by Mr. W. F. Fiske in Texas, and by Dr. J. B. Smith (1899) in New Jersey. In the South, however, its principal injury is effected at the base of living pine trees, /where its attack causes large scars, usually recognized as basal fire wounds. It has been found in practically all of the pines within its range, and a few specimens were taken by Mr. Fiske excavating galleries in spruce in the high mountains of North Carolina. A few specimens, taken b}T the writer in West Virginia from yellow and white pines, appear to represent quite a distinct variety of the normal southern form, while specimens of the normal form were taken from scrub and pitch pine at Kanawha Station, W. Va. The princi- pal distribution of the species is south of the area occupied by the red turpentine beetle, but the two overlap along the middle Atlantic States from North Carolina to Long Island, New York, and along the mountains from North Carolina to Pennsylvania. In its southern distribution it is often found in large numbers in the stumps of felled trees wherever winter and spring timber-cutting operations are carried on, and in lightning or fire-injured trees, but especially in the bark at the base of pine trees killed or injured by other insects. It shows a preference for the base of pine trees and stumps, but will breed in the bark on the underside of prostrate trunks. The parent beetles excavate their broad, irregular, sometimes branched, longitudinal egg galleries for a distance of a few inches to many feet, through the inner, living bark. If the bark is living, healthy, and full of resin, the progress in making an entrance through the inner bark and extending the galleries is slow, so that often a large mass of resin, or so-called pitch, is ejected through the entrance burrow before the beetles overcome this obstacle. In the meantime the adults will often be found active, even when literally imbedded in the semiliquid mass of resin. The gallery is first extended upward above the entrance, though later it may be extended downward, or, if there is but little resin, downward from the start. Ten to forty, or more, eggs are placed in an elongated mass at intervals along one or both sides of the gallery. When the larvae hatch they proceed in a body to feed on the bark and ultimately excavate a cavity, often many square feet in extent, which crosses and obliterates the primary gallery. When these large brood or larval chambers are excavated 150 THE SCOLYTID BEETLES. in the bark of a living tree, they are often found filled with liquid resin, yet the larva? will continue their work, apparently undisturbed by it. The larvae, which are stout, cylindrical, yellowish- white, foot- less grubs, with broad dorsal plates on the last abdominal segments armed with 6 stout spines, transform to pupae and adults in separate or adjoining cells in the borings in the larval chamber, or in separate cells extended from the margin or into the roof of the chamber. TThen the broods cf adults are fully developed and ready to emerge they usually bore through the intervening bark and congregate in the main chamber, where they mate and await the proper time for them to emerge. They then bore a few exit holes, or utilize the ventilatine holes in the old gallery, through each cf which many individuals emerge. In localities where this species is abundant it sometimes congregates in swarms of greater or less extent, accompanied by associates, guests, and enemies (see pp. 159-160). ECONOMIC FE-OTTTiES. In general, this species is of secondary importance in its relation to the death of pine timber, but occasionally it has been found in role of the primary and only cause of the death of trees, especially on Long Island. Xew York, and in Xew Jersey. The principal injury, however, is usually confined to the base of living pine trees. The broad larval chambers separating the bark over areas of greater cr less extent might in many cases heal without serious harm, but the dead bark, with the pitch masses on the outside and the dried resin and borings beneath, offers the most favorable conditions for subse- quent injuries by forest foes, and thus these larval chambers are the primary cause of a very large percentage cf the so-called "foe scars" cr foe wounds which are so prevalent at the base and lower portic n c f the trunks of living t:ves in the South. If a forest tire burns the bark and resin and exposes the wood, it becomes dry and is usually mined by round-headed and flatheaded wood-borers. Or the v. may become either pitchy or decayed, so that the next lire burns d:eply into it and kills a larger area of the bark. Thus each subse- quent fire contributes to an extension of the wound until hi many eases the tree is so weakened that it is broken down by wind or attacked and killed by other barkbeetles. In the aggregate, primary injury by the beetle results in very extensive losses of some of th umber. EVIDENCES F ATTACK. The first evidences of the work of the beetle are found in fresh masses of pitch, or large pitch tubes, mixed with reddish borings, at or near the base i i living trees and the stum] - - ently felled ones. Subsequent evidence, until destroyed by fire, is found in the old pitch THE GENUS DENDROCTONTJS. 151 masses on the surface, traces of primary galleries under the bark or on the wood, or round holes in the loose dead bark over the wound. The commercial value of the trees attacked by this beetle is not materially affected until after the injury has been extended into the trunk b}^ fire, wood-boring insects, decay, etc., to a point where the vitality is greatly reduced or the tree becomes worthless. FAVORABLE AND UNFAVORABLE CONDITIONS FOR THE BEETLE. Favorable conditions for the multiplication of this beetle and its injury to living timber are found in sections where for several years a large amount of pine timber has been killed or injured by insects, or felled and broken by storms, lumbering operations, etc., followed by a year in which no timber dies or is injured or killed. Under these conditions the vast numbers of this insect which have bred in the injured and dying trees will, through necessity, attack the living- trees and cause serious and widespread damage the first year. This will usually be followed by little or no damage in succeeding years, unless favorable conditions are again presented for their multipli- cation. The first year after the disappearance of the southern pine beetle in West Virginia the swarms of the red turpentine beetle caused extensive injuries to the base of living trees, but for many years thereafter the species was rare and did no harm. Unfavor- able conditions for injury to living trees by this insect are found in healthy forests under a system of forest management which requires more or less continuous timber-cutting operations to utilize the older matured, injured, and dying trees. METHODS OF CONTROL. Since the habits of this beetle and the character of the injury caused by it are in marked contrast to those of nearly all other species of the genus, the problem of control is quite different. The principal injury is to the base of living trees, which, in itself, may be slight, but when aggravated and extended by subsequent and quite different causes may become quite extensive. Therefore the object should be to prevent the primary injury by preventing the undue multiplication of the beetle, or by furnishing a continuous supply of more attractive breeding places, as in the case of continued lumber- ing operations. The first may be accomplished if within quite an extensive area the infested bark is removed from the base of insect- killed, lightning-struck, and otherwise injured or dying trees, as well as from the stumps of those felled during local or sporadic timber- cutting operations. This work should be done during the fall and winter following infestation, beginning with the first of September and ending with the first of March. Where only a few trees in a lawn 152 THE SCOLYTID BEETLES. or park are involved, or even where many are attacked in a forest under a complete system of forest management, serious injury may be prevented by cutting the beetles out of the bark with a chisel or knife as soon as the discharge of resin on the bark indicates their presence; or they can often be killed quickly and effectually by means of a stout wire inserted into the entrance burrow, if done before the parent beetles have extended their galleries into the inner bark beyond 2 or 3 inches. It appears that in places where continued timber-cutting opera- tions are carried on there are sufficient and most attractive breeding- places for this beetle; therefore in such sections little or no damage to the living and otherwise uninjured trees will result. If the cutting should be discontinued for one or more years throughout a large L--r->— -TV Fig. 96. — The black turpentine beetle: Distribution map. (Author's illustration.) area, and if it seems desirable, the infested bark may be removed from the majority of the stumps of trees felled during the fall, winter, and spring, or the brush piled around the stumps and burned, the work to be done during the fall and winter following the cutting. In case the removal of the bark from the stumps is required in timber-cutting contracts, it should be specified that the bark must not be removed until after it becomes infested with broods of larva1, or, in other words, the stumps of trees felled in the fall, winter, and spring should not be barked to destroy the broods of this beetle before the following June or July, but the barking must be com- pleted before the following March. Trees felled during the spring and summer to serve as traps should not have the bark removed for at least two months after such operation. THE GENUS DENDROCTONUS. 153 In some sections of the country this beetle appears to be attracted to the trunks of felled trees much more than in others, depending probabl}r on the species of tree and local conditions relating espe- cially to the presence or absence of certain other insects which would or would not interfere with the development of their broods. BASIS OF INFORMATION. Information in regard to this beetle is based on investigations by the writer in West Virginia, at Romney, July, 1891; at Dellslow, March and November, 1891; at Crow, April, 1893; in Randolph County, in spruce forest, May, 1893; at Kanawha Station, July, 1903; in North Carolina, at Fletchers, July and November, 1902; at Tryon, July, .1902, March, 1903, and October, 1903; at Boardman, Novem- ber, 1904; at Lumber, S. C, March, 1903; at Kirbyville, Tex., November, 1902; on Long Island, New York, September, 1903; at Roosevelt, W. Va., and Virginia Beach, Va., June, November, and December, 1907; on investigations by Mr. W. F. Fiske in North Carolina, at Tryon, March, April, May, and November, 1903, Novem- ber, 1904, and March, May, and July, 1905; at Pisgah Ridge Moun- tain, September, 1904; at Pink Beds, September, 1904, and May, 1905; at Biltmore, May, 1905; at Cornelia, Ga., November, 1903; at Thomasville, Ga., March, 1905; at New Landing, S. C, August, 1903; at Chicora, S. C, November, 1904; at Call, Tex., February, 1905, and at Deweyville, Tex., March, 1905. Additional localities through correspondence and from other collections are : New Brunswick and Lakewood, N. J.; Islip, Long Island, New York; Calhoun, Ala.; Tark- ington and Austin, Tex.; Tampa, Fla., and Marion County, Fla.; Glen Allen and Fort Monroe, Va. Represented in the forest-insect collection of this Bureau by over 400 specimens, including all stages and work. BIBLIOGRAPHY. (Refers to D. terebrans proper and not to D. valens Lee, which was often confused with it.) Le Baron, 1871; Packard, 1890, p. 721; Hopkins, 18936, p. 143; Hopkins, 1893c, p. 213; Hopkins, 1894a, pp. 71-76; Hopkins, 1897a, p. 41; Hopkins, 1899a, pp. 302-393, 415, 421, 447; Smith, 1899, p. 364; Hopkins, 19026, p. 10; Hopkins, 1906c, p. 81; Hopkins, 1909, pp. 147-150. No. 23. THE RED TURPENTINE BEETLE. (Dendroctonus valens Lec.a Figs. 97-102.) The red turpentine beetle is a large, stout, light to dark red, cylin- drical barkbeetle, 5.7 to 9 mm. in length, with head broad, convex/lack- ing grooves or longitudinal impressions; the pronotum broad, coarsely a Referred to under Dendroctonus terebrans in earlier literature. 154 THE SCOLYTID BEETLES. punctured, becoming finer toward base, the sides slightly narrowed toward the head, but not strongly constricted; the elytra with coarse, transverse to oblique rugosities between distinct to obscure rows of punctures; the declivity convex, with moderately deep grooves, and the intervening spaces slightly convex and roughened; the entire body sparsely clothed with long hairs. (See fig. 97.) It attacks the living bark on injured, dying, healthy, and felled pine and spruce in eastern United States and Canada, north from the mountains of North Car- olina, westward to the Pacific coast, and south- ward from British Co- lumbia into Mexico. The parent beetles excavate broad, somewhat irregu- lar, winding, longitudi- nal egg galleries (fig. 98) through the inner bark and groove the surface of the wood. The eggs are placed in groups or masses at intervals along the sides of the galleries. The stout, yellowish- white, cylindrical larva?, with reddish heads and stout spines on the dorsal plates of the last ab- dominal segments, do not make separate larval mines, but all feed to- gether and eat out cavi- ties in the inner bark from a few inches square to several feet square (see fig. 98). They transform to pupae and adults in separate or closely joined cells in the inner bark, or inner portion of the outer bark, or in mines extending from the social cham- ber. The broods work independently of other species and occupy and separate the bark around the base of trees and stumps (see Hg. 99), often extending their work for a foot or more onto the roots beneath the surface, and the broad larval chambers are often filled with semiliquid resin, without injury to the occupants. The Yig. 97.— The red turpentine beetle (Dcndroctonus valens): Adult. Greatly enlarged. (Authorsillustration.) (Seealso fig. 4, larva: rig. 5. pupa.1) THE GENUS DENDROCTONUS. 155 attack on living trees and on the stumps of those recently felled is indicated by large masses of pitch and pitch tubes, mixed with reddish borings. SEASONAL HISTORY. OVERWINTERING STAGES. The winter is passed in and beneath the bark of trees and stumps attacked the preceding spring and summer, as parent adults, larva?, and developed broods, the larvae, as a rule, occupying the bark on the roots beneath the surface of the ground. Fig. 98.— The red turpentine beetle. Egg galleries and larval chamber: A, Incomplete egg galleries with boring dust removed; B, normal gallery; C, advanced stage of work; a, entrance burrow; b, basal section; c, ventilating burrow; d, egg nest with eggs; e, boring dust; /, subsequent or inner galleries; g, larvae at work; h, pupal cell in boring dust mixed with resin. (Author's illustration. ) ACTIVITY OF OVERWINTERED BROODS. The overwintered parent adults begin to extend their galleries during the first warm weather in March, April, or June, depending on locality, and probably continue to work in these, or excavate new galleries, until July and August, or later. It is probable that after finishing one gallery they emerge and excavate new ones, and that this process may be repeated during the summer and fall. It is also not improbable that some of them may pass the second winter. The overwintered broods of young adults begin to emerge from the bark in April and continue to do so during May and June, and less com- monly until August, or later; they excavate galleries principally in 156 THE SCOLYTID BEETLES. May and June, and continue activity until hibernation begins in the fall. The overwintered broods of large larva? evidently complete their development to pupae and adults and emerge by July, while the young larvae may not complete their development and emerge until in September and October, and some individuals may pass the second winter as adults. GENERATION. The overwintered broods of adults evidently begin to excavate galleries and deposit eggs in the period from April to June, depending on latitudes and altitudes, and continue their activity as successive broods emerge, during June, July, August, and until September, or later. The eggs begin to hatch probably within a week or ten days after they are deposited. This process continues during Ma}" and June or July, until September, or later. The larval development is principally during July, August, and September, but continues until hibernation begins. The more advanced larvae begin to transform to pupae and adults in August, while some of the others continue trans- v formation during September and October, until cold weather, when larvae of all stages, pupae, and adults are found. While it is possible that some of the more advanced broods in the warmer localities may emerge in the late summer or early fail, it is evident that by far the greater number pass the winter in the bark, where they develop and emerge in the following spring and summer. The possibility of individuals of the overwintered parent adults, as well as of young adults of the overwintered brood, excavating more than one gallery, during the season, together with the probability that some individuals of a single generation may pass through two or even three winters, involves such an overlapping of broods of different generations that even with extensive observations it has been impos- sible to arrive at any definite conclusions regarding the normal period required for the development and emergence of all of the broods of a generation. HABITS. This species prefers to enter the bark of injured or dying trees or that of the stumps and logs of those which have been felled, but often attacks the perfectly healthy bark on the base and roots of healthy, living trees. It has been found in practically all of the eastern pines and spruces within its range of distribution, and in nearly all of the principal western pines, but in none of the western spruces except the white spruce in the Black Hills of South Dakota. It is probable that none of the species of pine and spruce growing within its range is exempt from its attack. We have no records of it in fir (Abies), or in Doug- THE GENUS DENDROCTONUS. 157 las fir, and it is not likely that it will infest these trees, but it has been found in the eastern larch. It is often exceedingly abundant in the stumps of felled trees where timber-cutting operations are carried on, in fire-scorched trees, and especially in the bark at the base of those killed by other species of Dendroctonus, or by lightning, or storm, or otherwise injured and broken. It shows a decided preference for the bark on the base of Fig. 99.— The red turpentine beetle. Work in bark at base of tree: a, Entrance and pitch tube; b, egg gallery; c, borirlg dust and resin; d, pupal cell; e, pupa; /, larvse at work feeding on inner living bark; g, exit burrows; h, resulting old scar or basal wound, often referred to as basal fire wound; i, inner bark with outer corky bark removed. (Author's illustration.) pine trees and stumps, and is rarely common in the logs or prostrate trunks, even of pine. The parent beetles excavate their broad, irregular, sometimes branched, longitudinal egg galleries, from a few inches to many feet in length, through the inner living bark. If the bark is living and healthy and full of resin, the progress in making an entrance through the inner bark and extending the galleries is slow, and often large masses of resin or so-called pitch are pushed out at the entrance before 158 THE SCOLYTID BEETLES. they overcome this obstacle. In the meantime the adults will often be found active, even when literally embedded hi the semiliquid mass of resin. The gallery is first extended in one direction above the entrance, but later it may be extended below, or, if there is but little resin, may extend downward from the start. Ten to forty or more eggs are placed in an elongated mass along one or both sides of the gallery, and when the larvae hatch they proceed in a body to feed on the bark and ultimately excavate a cavity, often many square feet in extent (fig. 101), which crosses and obliterates the primary gallery. When these large social brood or larval chambers are excavated in the Fig. 100. — The red turpentine beetle: Basal wound in living tree resulting from primary injury by this species. Often mistaken for tire wound. (Author's illustration,) bark of a living tree, they are often found filled with liquid resin, yet the larvae will continue their work, apparently undisturbed by it. The larva1, which are stout, cylindrical, yellowish- white, footless grubs, with broad dorsal plates on the last abdominal segments armed with six stout spines, transform to pupa? and adults in separate or adjoining cells in the borings in the larval chamber or in separate cells extended from the margin or into the roof of the chamber. When the broods of adults are fully developed and ready to emerge, they usually bore through the intervening bark and congregate in the mam chamber, where they mate and await the proper time for them to THE GENUS DENDROCTONUS. 159 emerge. They then bore a few exit holes or utilize the ventilating holes in the old gallery, through each of which many individuals emerge. In localities where this barkbeetle is abundant it sometimes congregates in swarms of greater or less extent, accompanied by asso- ciates, guests, and enemies. The flight habits of all of the species of Dendroctonus are more or less obscure, but some observations have been made on the swarm- ing habits of this species, as recorded by the writer in Bulletin No. 56 of the West Virginia Agricultural Experiment Station, pa^es 346-348, which are perhaps worthy of repetition in this connection: » Fig. 101.— Western yellow pine showing work of the red turpentine beetle, Flagstaff, Ariz. (Original.) Returning to Morgantown, W. A'a., on May 12, I learned from my assistant, Mr. W. E. Rumsey, and others, that a great swarm of barkbeetles had passed through Morgantown on May 4. They were especially abundant in and around furniture factories and new houses that were being painted, and wherever there was an odor of turpentine. In fact, they came, as it was expressed, "like a hailstorm," into open windows and doors, and were the cause of considerable alarm on the part of the inhabitants, who thought that a plague of bugs had visited the place. The new greenhouses that were being constructed and painted at the experiment station were central points of attraction. Here they occurred like swarms of bees. While this remarkable swarm consisted mainly of the turpentine barkbeetles, it would appear from the dead and living examples that I found in the greenhouses and adhering to the paint that it was accompanied by numerous species of bark and timber beetles and also by some of their enemies. I was greatly disappointed that 160 THE SCOLYTID BEETLES. I did not see this swarm or the many others like it which I subsequently learned occurred in different sections of the State about the same time, since it would have been very interesting and important to know the number of species that occurred in them and the approximate proportions of each. a On my way to the spruce forests on May 20, I was informed at Bretz, Tucker County, W. Va., that the swarm had occurred there on April 30. They came from the southeast and ''showered against the windows like hail,'' and entered through the open doors into the houses in such numbers that they had to be swept out. I found a few examples of the turpentine beetle in the office of Mr. Shaw, who informed me that it was the same insect that occurred in the swarm. At Mr. Frank Bennet's, about 15 miles farther up the river (Dry Fork of Cheat), I learned that a similar swarm had visited that section about the same time as the one at Bretz. Here I found large numbers of the turpentine beetle in the webs of the apple tree tent cater- pillar. The swarm that passed through Bretz and Morgantown doubtless originated in the dead pine timber of Hampshire, Hardy, and Pendleton counties, and taking a northwesterly course passed over the Allegheny Mountains and through the great spruce forests of Randolph and Tucker counties about April 30, and reached Mor- gantown on May 4. The swarm was also reported from different points along the West Virginia and Pittsburg Railroad and from Pocahontas and Greenbrier counties, which would indicate that this remarkable occurrence was quite general throughout the spruce and pine areas. The fact that the turpentine beetle had been found so common attacking living trees and occurred in such enormous numbers in these swarms, together with the fact that numerous other species occurred in the swarms and in the bark of dying trees, led one very naturally to the conclusion that even if the destructive species had become extinct the timber would continue to be killed by these surviving barkbeetles. The vast numbers of the red turpentine beetle which had bred in the trees killed by the southern pine beetle during 1891 and 1892, finding no more trees dying from this cause in 1893, attacked the base of living pine and spruce, and did considerable damage during the summer of 1893, but there was little or no damage caused by it in 1894, and for many years thereafter jt was a rare insect in the coniferous forests of West Virginia examined by the writer. ECONOMIC FEATURES. In general, this species is of secondary importance in its economic relations to American forests. In the East it has never been found as the primary and only cause of the death of trees; in California, both at Monterey and in the Sierra Nevada Mountains, it is more aggres- sive, and it appears that numbers of trees have been killed or se- riously damaged by it. The principal injury is to the base of living "The species found in the greenhouses and on paint which evidently came in the swarm, May 4, 1893, are as follows: 1. Monarthrum mali Fitch. 7. J iylu rgops glabratus Zett. 2. Gnathotrichus materiarius Fitch. 8. Dendroctonus terebrans 0\W.[=rakns 3. Xyleborus xylographux Say. Lee, which greatly predominated in 4. Tomicus cacographus Lee. the swarm.] 5. Hylastes cavernosus Zimm. 9. Ipsfasciatus Oliv. (i. Jhjlastes gracilis Lee. THE GENUS DENDROCTONUS. 161 pine and spruce, especially the former. While it sometimes infests the bark 8 or 10 feet above the base and in sufficient numbers to kill a few trees, it is an abnormal habit and result. It sometimes com- pletely separates the bark around the base, but the wounds are so completely covered by resin that a tree so affected rarely dies from this injury alone, but often from secondary injury by fire or other insects. The broad larval chambers separating the bark over areas of greater or less extent might in many cases heal without serious harm, but the dead bark with the pitch masses on the outside and the dried resin and borings beneath offer the most favorable conditions for subse- quent injuries by forest fires, and thus are the primary cause of a very large percentage of the so-called "fire scars" or fire wounds (fig. 100) which are so prevalent at the base and lower portion of the trunks of living trees in the dry pine areas of the western mountains. One or more years after the injury by the beetle, a forest fire may burn the bark and resin and expose the wood, which becomes dry and is then bored by round-headed and flat-headed wood-borers, or it becomes pitchy or decayed, so that the next fire burns deep into the wood and kills a larger area of the bark. Thus each subsequent fire con- tributes to an extension of the wound until in many cases the tree is so weakened that it is broken down by wind or attacked and killed by other barkbeetles. In the aggregate, this primary injury by the beetle results in very extensive losses of some of the best timber. EVIDENCES OF ATTACK. The first evidence of the work of the beetle is found in the fresh masses of pitch or large pitch tubes, mixed with reddish borings, at or near the base of living trees and stumps of recently felled ones. Subsequent evidence, until destroyed by fire, is found in the old pitch masses on the surface or traces of primary galleries under the bark or on the wood, and round holes in the loose, dead bark over the wound. EFFECTS ON COMMERCIAL VALUE OF THE WOOD. The commercial value of the trees injured by this beetle is not materially affected until after the injury has been extended into the trunk by fire, wood-boring insects, decay, etc., to a point where the vitality is greatly reduced or the tree becomes worthless. FAVORABLE AND UNFAVORABLE CONDITIONS FOR THE BEETLE. Favorable conditions for the multiplication of this beetle and for its injury to living timber are found in sections where for several years a large amount of pine timber has been killed or injured by insects, or felled and broken by storms, lumbering operations, etc., followed by a year in which no timber dies or is injured or killed. Under these con- 89535— Bull. 83, pt. 1—09 12 162 THE SCOLYTID BEETLES. ditions the vast numbers of this insect which have bred in the in- jured and dying trees will, through necessity, attack the living trees and cause serious and widespread damage the first year. This will usually be followed by little or no damage in succeeding years, unless more favorable conditions are again presented for their multiplication. Unfavorable conditions for injury to living trees by this insect are found in healthy forests under a system of forest management which requires more or less continuous timber-cutting operations to utilize the older matured, injured, and dying trees. METHODS OF CONTROL. Owing to the peculiar habits of this beetle and the character of the injury caused by it, contrasting strongly with those of other species of the genus except the black turpentine beetle, the problem of control is quite different from that relating to nearly all of the other species. The principal injury is to the base of living trees, which, in itself, may be slight, but when aggravated and extended by subsequent and quite different causes may become quite extensive. Therefore the object should be to prevent the primary injury, by preventing the undue mul- tiplication of the beetle or by providing more attractive and con- tinued breeding places. The first may be accomplished within quite an extensive area if the infested bark is removed from the base of insect-killed, lightning-struck, and otherwise injured or dying trees, as well as from the stumps of local or sporadic timber-cutting oper- ations, the work to be done during the fall and winter following infesta- tion, beginning with the first of September and ending with the first of March. When only a few trees in a lawn or park are involved, or even where many are attacked in a forest under a complete system of forest management, serious injury may be prevented by cutting the beetles out of the bark with a chisel or knife, as soon as the discharge of resin on the bark indicates their presence. Often they can be killed quickly and effectually by means of a stout wire inserted into the entrance burrow, if done before the parent beetles have extended their galleries in the inner bark beyond 2 or 3 inches. It appears that continued timber-cutting operations offer sufficient and more attractive breeding places for this beetle. Therefore, in sections where these are carried on little or no damage to the living and otherwise uninjured trees will result ; but if the cutting should be dis- continued for one or more years throughout a large area the infested bark should be removed from the majority of the stumps of trees felled during the fall, winter, and spring, the work to be done during the fall and winter following the cutting. In case the removal of the bark from the stumps is required in timber-cutting contracts, it should be specified that the bark must not be removed until after it becomes infested with broods of larvae, THE GENUS DENDROCTONUS. 163 or, in other words, the stumps of trees felled in the fall and winter should not be barked to destroy the broods of this beetle before June or July, but the barking must be completed before the following March. Trees felled during the spring and summer to serve as traps should not have the bark removed for at least two months after the trees are felled. In some sections of the country this beetle appears to be attracted to the trunks of felled trees much more than to those of others, depending probably more on the species of tree and local conditions relating especially to the presence or absence of certain other insects which would or would not interfere with the development of their broods. In the vicinity of Monterey, Cal., it was found by the writer abun- dant in September in the bark of trees felled by storm the previous April. This suggested the utilizing of trap trees in such localities to attract the beetles to the bark of the trunks, as well as to that on the stumps. BASIS OF INFORMATION. The above statements are based on investigations by the writer in many localities in different sections of West Virginia in 1890 to 1894; at McCloud and Berkeley, Cal., Grants Pass and Albany, Oreg., near Spokane, Wash., and at Moscow, Idaho, April to June, 1899; in the Black Hills, South Dakota, 1901 and 1902; at Priest Lake, Idaho, August, 1902; at Del Monte and Monterey, Cal., Sep- tember, 1902; at Williams, Ariz., Septejnber, 1902; at Vermejo, N. Mex., May, 1903; at Flagstaff, Ariz., May, 1904; in the Yosemite National Park, California, June, 1904; at Brunswick and Portland, Me., May and June, 1900; at Maiden, Wyoming [Melrose], and Lynn Woods, Mass., May, 1906 (in Norway spruce defoliated by gipsy moth); at Milford, Pa., May, 1905; at Pink Beds, N. C, July, 1904; at Manitou Park and Palmer Lake, Colo., October, 1905; in Ventura County, Cal., June, 1904; at Garland, Colo., June, 1906; on Grand Island, Michigan, July, 1907; by Mr. W. F. Fiske, at Webster, N. H., June, 1904; at Pink Beds, N. C, May, 1905; on Grand Island, Michi- gan, October, 1906; at Capitan and Cloudcroft, N. Mex., March to May, 1907; by Mr. J. L. Webb, in the Black Hills, South Dakota, June to October, 1902; at Flagstaff, Ariz., June to August, 1904; in the vicinity of Centerville, Idaho, May to August, 1905; in the Cap- itan Mountains, Lincoln National Forest, and White Mountains, New Mexico, and in the Chiricahua National Forest, Arizona, June to September, 1907; by Mr. H. E. Burke, at Palo Alto, Cal., May, 1905, May, 1906, and September, 1906; in the Yosemite National Park and vicinity, at Wawona, Summerdale, Little Yosemite, and Yosemite, Cal., May to September, 1906; at Kamas, Panguitch, and Panguitch 164 THE SCOLYTID BEETLES. Lake, Utah, Joseph, Oreg., and Palo Alto and Pacific Grove, Cal., June to October, 1907. Additional localities through correspondence and from other collections are: Missoula and Ovondo, Mont.; Fredonia, Paradise, Williams, Flagstaff, and Tucson, Ariz.; Franconia and Pike, Fig. 102.— The red turpentine beetle: Distribution map. (Author's illustration.) N. H.; Orono and Limerick, Me.; Glen Allen, Va.; Le Moin, Visalia. Ventura County, Sisson, Placer County, Siskiyou County, and Duns- muir, Cal. ; Kansas ; Helena. Mont. ; Coldridge, N. Mex. ; Powder River, Custer County, Colo.; Skykomish River, Washington; Hood River. THE GENUS DENDROCTONUS. 165 Oreg.; Coeur d'Alene, Idaho; Duluth, Minn.; Marquette, Mich.; Cam- bridge, Mass.; Chalco, Chihuahua, Mexico City, Michoacan, Ponada, and Satazin, Mexico. It is represented in the forest-insect collec- tions of the West Virginia Agricultural Experiment Station and of the Bureau of Entomology by more than 5,000 specimens. While specimens from all over the country are included under one name, it is believed by the writer that there are a number of more or less distinct so-called races and varieties, and possibly some forms are specifically distinct, but, owing to the great variation in all deter- mined characters which can be used for such a separation, it is thought best to leave all of them under one name. The species is easily separated from the southern turpentine beetle by its light to dark red color, except when compared with the immature reddish specimens, and then the coarser punctures on the prothorax and coarser teeth of the tibia of the latter will serve to indicate the difference. BIBLIOGRAPHY. Harris, 1841 (under Dendroctonus terebrans), p. 72; Harris, 1842 (under D. terebrans), pp. 72-73; Harris, 1852 (under D. terebrans), p. 76; Harris, 1862 (under D. terebrans), p. 86; Harris, 1863 (under D. terebrans), pp. 84-86; Thomas, 1876 (under D. terebrans), p. 146; Smith, 1897 (under Hylurgus terebrans), p. 52; Packard, 1887 (under D. tere- brans), pp. 175 and 243; Packard, 1890 (under D. terebrans), p. 721; Hopkins, 1892a, (under D. terebrans), pp. 64-65; Hopkins, 1899a (under D. terebrans), pp. 392-393, 415-421, 447; Hopkins, 18996 (under D. terebrans), pp. 14-15; Hopkins, 19026, p. 12; Hopkins, 1903a, p. 61; Felt, 1903 (under D. terebrans), pp. 480-481; Hopkins, 1904, p. 19; Hopkins, 1905, pp. 11, 17; Hopkins, 1906c, p. 81; Felt, 1906 (under D. tere- brans), pp. 342-345, 348, 776, 792, 796; Hopkins, 1909, pp. 151-157. GENERAL BIBLIOGRAPHY. (Economic literature.) 1826. Harris, T. W.— Trees. r-~- , ST c kZ v IB CD «« of Entc ~?J and ptent ATiONAL AGRICULTURAL LIBRA HUM llll I II 111 II 11:111111111111 1022857641