Historic, archived document Do not assume content reflects current scientific knowledge, policies, or practices. « SN Val ae h pe m2. UE PARTMENT OF:AGRICULTURE. DIVISION OF ENTOMOLOGY. BULLETIN No. 10. | (SECOND, REVISED EDITION.) CUE Ee ates BA Dee Saw ale Ses AND THEIR INSECT DEFOLIATORS. BEING A CONSIDERATION OF THE FOUR MOST INJURIOUS SPECIES WHICH AFFECT THE TREES OF THE CAPITAL; WITH MEANS OF DESTROYING THEM. eas yes et Ey, ENTOMOLOGIST. —_—__—=< ee ____—___ WASHINGTON: GOVERNMENT PRINTING OFFICE. 18S8. 21061— Bull 10 = ——— ee — eee eee : a CONTENTS. ERR foe doll cua wwe tw a cmp wets cng ae ee am oa wien wen necnn vows oj aa angeis ots Treatment with London purple. ..---- ..-----+--+ ee ee ate fC ee Effects of the mixture ...--- Pee 5 oe Pe Ee has Ee ee ee Treatment with Paris green...--.-.----.---- Se Or Se Pee See Mechanical means of applying the poison ........-+--+---++----- aa wat Ve i EY SS 8 2124 ile lt gel Sei gee ge A ol ee, age Sexes See HABITS AND NATURAL HISTORY .-...... a Ee eee 2 Oe ae = itn Saale omc cian os bd we sm me Ee pe ee eee ee ae ee OMe ORE Anos oes eu = oo eee oe aonwidcep eens uo om I aoe ode a eale asa os iate hase ee kan SG We eeeindele sss woe Pee eR rEIREL WNABGI 242 SOS So fers rows, if the surface of the leaf per- tion ou ieat tavine caus cdo view, Dy pews wits it. In three instances those ‘ "8° deposited by a single female were counted. The result was 394, 427, and 502, or on an average 441 eggs. But in addition to such large clusters, each female will deposit eggs in smaller and less regular patches, so that at least 500 eggs may be considered as the real num- ber produced by a single individual. The egg, measuring 0.4 millime- ters, is of a bright golden-yellow color, quite globular, and ornamented by numerous regular pits, which give it under a magnifying lens the appearance of a beautiful golden thimble. As the eggs approach the time of hatching this color disappears and gives place to a dull leaden hue. ‘The interval between the time of depositing and hatching of the eggs for the first brood varies considerably, and the latter may be greatly retarded by inclement weather. Usually, however, not more than ten days are consumed in maturing the embryo within. The eggs of the summer brood seldom require more than one week to hatch. ‘Without check the offspring of one female moth might in a single season (assuming one-half of her progeny to be female and barring all checks) number 125,000 caterpillars in early fall—enough to ruin the shade-trees of many a fine street. 38 OUR SHADE TREES AND THEIR INSECT DEFOLIATORS. The Larva (Fig. 18, a, b, and c).—‘ The caterpillars just born are pale yellow, with two rows of black marks along the body, a black head, and with quite sparse hairs. When full grown they generally appear pale yellowish or greenish, with a broad dusky stripe along the back and a yellow stripe along the sides; they are covered with whitish hairs, which spring from black and orange-yellow warts. The caterpillar is, Fic. 18.—Hyphantria cunea: a, dark larva, seen from side; 5b, light larva from above; c, dark larva from above; d, pupa from below; e, pupa from side; f, moth. however, very variable both as to depth of coloring and as to mark- ings. Close observations have failed to show that different food pro- duces changes in the coloration; in tact, nearly all the various color varieties may be found upon the same tree. The fall generation is, however, on the whole, darker with browner hairs than the spring gen- eration. ‘*‘As soon as the young caterpillars hatch they immediately go to work to spin a small silken web for themselves, which by their united efforts _ soon grows large enough to be noticed upon the trees. Under this pro- — tecting shelter they feed in company, at first devouring only the green upper portions of the leaf and leaving the veins and lower skin unmo- lested. As they increase in size they enlarge their web by connecting it with the adjoining leaves and twigs; thus as they gradually work downwards their web becomes quite bulky, and, as it is filled with brown and skeletonized leaves and other discolored matter, as well as with their old skins, it becomes quite an unpleasant feature in our public thoroughfares and parks. The caterpillars always feed underneath these webs; but as soon as they approach maturity, which requires about one month, they commence to scatter about, searching for suitable places in which to spin their cocoons. If very numerous upon the same tree the food-supply gives out, and they — are forced by hunger to leave their sheltering homes before the usual — time. . i ah Dee i THE FALL WEB-WORM. 39 ‘When the young caterpillars are forced to leave their webs they do not drop-suddenly to the ground, but suspend themselves by a fine silken thread, by means of which they easily recover the tree. Grown caterpillars, which measure 1.11 inches in length, do not spin such a thread. Both old and young ones drop themselves to the ground without spinning when disturbed or sorely pressed by hunger. Pupa and Cocoon.—* Favorite recesses selected for pupation are the erevices in bark and similar shelters above ground; in some cases even the empty cocoons of other moths.* The angles of tree-boxes, the rub- bish collected around the base of trees and other like shelter are em- ployed for this purpose, while the second brood prefer to bury them- selves just under the surface of the ground, provided that the earth be soft enough for that purpose. The cocoon itself is thin and almost transparent, and is composed of a slight web of silk intermixed with a few hairs, or mixed with sand if made in the soil. ‘‘The pupa (Fig. 18, d and e) is of a very dark-brown color, smooth and polished, and faintly punctate; it is characterized by a swelling or bulging about the middle. It is 0.60 inch long and 0.23 inch broad in the middle of its body, or where it bulges a little all round. The Moth (Fig. 18, b).—“‘ The moths vary greatly, both in size and coloration. They have, in consequence .of such variation, received Fic. 19.—Hyphantria cunea: a-j, wings of a series of moths, showing the variations from the pure white form to one profusely dotted with black and brown. many names, such as cunea Drury, textor Harr., punctata Fitch, puncta- tissima Smith (Fig. 19). But there is no doubt, as proven from frequent breeding of specimens, that all these names apply to the very same insect, or at most to slight varieties, and that Drury’s name cunea, hay- ing priority, must be used for the species. ‘The most frequent form observed in the vicinity of Washington js white, with a very slight fulvous shade; it has immaculate wings, * We have known the substantial cocoon of Cerwra to be used for fhis purpose. 40 OUR SHADE TREES AND THEIR INSECT DEFOLIATORS. tawny-yellow front thighs, and blackish feet; in some specimens the tawny thighs have a large black spot, while the shanks on the upper surface are rufous. In many all the thighs are tawny yellow, while in others they have scarcely any color. Some specimens (often reared from the same lot of larve) have two tolerably distinct spots on each front wing—one at base of fork on the costal nerve and one just within the second fureation of the median nerve. Other specimens, again, have their wings spotted all over, and approach the form punctatissima, ‘described as the ‘‘ Many-spotted Ermine-moth” of the Southern States. The wings of the moths expand from 14 inches to 13 inches. The male moth, which is usually a little smaller, has its antenne doubly feath- ered beneath, and those of the female possess instead two rows of minute teeth. ‘The pupa state lasts from six to eight days for the summer brood, while the hibernating brood, however, requires as many months, ac- cording to the latitude in which they occur. INJURY DONE IN 1886. ‘‘ During the past year the city of Washington, as well as its vicinity, was entirely overrun by the caterpillars. With the exception of trees and plants the foliage of which was not agreeable to the taste of this. insect, all vegetation suffered greatly. The appended list of trees, shrubs, and other plants shows that comparatively few kinds escaped | entirely. The fine rows of shade trees which grace all the streets and avenues appeared leafless, and covered with throngs of the hairy worms. Excepting on the very tall trees, in which the highest branches showed a few leaves too high for the caterpillars to reach, not a vestige of foliage could be seen. The trees were not alone bare, but were still more dis- figured by old and new webs made by the caterpillars, in which bits of leaves and leaf-stems, as well as the dried frass, had collected, produc- ing avery unpleasant sight. The pavements were also constantly cov- ered with this unsightly frass, and the empty skins of the various molts the caterpillars had to undergo were drifted about with every wind, and collected in masses in corners and tree-boxes. The parks fared a little better. Because of the great variety of trees planted there some escaped entirely, while others showed the effect of the united efforts of so many hungry caterpillars only in a more or less severe degree. The grassy spots surrounding the different groups of trees had also a protective influence, since the caterpillars do not like to travel over grass, except when prompted by a too ravenous hunger. The rapid increase of this insect is materially assisted by the peculiar method of — selecting shade trees for the city. Each street has, in many cases, but one kind of shade tree; rows of them extend for miles, and the trees — are planted so close together that their branches almost interlace. Thus there is no obstacle at all to the rapid increase and distribution of THE FALL WEB-WORM. 41 the caterpillars. If different kinds of trees had been planted, soas to alternate, less trouble might be experienced. Plate I shows a view of Fourteenth street, taken late in September, which illustrates this point; the poplars on the west side being completely defoliated as -‘faras the eye can reach, while the maples on the east are almost un- touched. ‘As long as the caterpillars were young, and still small, the dif- ferent communities remained under cover of their webs, and only offended the eye. But as soon as they reached maturity, and com- menced to scatter—prompted by the desire to find suitable places to spin their cocoons and transform to pupe—matters became more unpleasant, and complaints were heard from all those who had to pass such infested trees. In many localities no one could walk without stepping upon caterpillars; they dropped upon every one and everything; they entered flower and vegetable gardens, porches and verandas, and the house itself, and became, in fact, a general nuisance. ‘The chief damage done to vegetation was confined to the city itself, although the caterpillars extended some distance into the surrounding country. There, however, they were more local, and almost entirely confined to certain trees, and mainly so to the White Poplar and the Cottonwood. Along the Baltimore and Potomac Railroad tracks these trees were defoliated as far as five miles from the Capitol. In George- town the caterpillars were equally noxious, but in the adjoining forests - but very few webs could be seen. ‘“‘The proportionate injury to any given species of tree is to some extent a matter of chance, and in some respects a year of great injury, as 1886, is not a good year to study the preferences of a species, be- cause when hard pressed for food the caterpillars will feed upon al- most any plant, though it is questionable whether they can mature and transform on those which they take to only under the influence of such absolute necessity. Again, the preference shown for partic- ular trees is more the result of the preference of the parent moth than of its progeny in a case of so general a feeder as the Fall Web-worm. We hada very good illustration of this in Atlantic City last autumn. The caterpillars were exceedingly abundant during autumn along this portion of the Atlantic coast, especially on the trees above named. We studied particularly their ways upon one tree that was totally defoliated by September 11. The bulk of the caterpillars were then just through their last molt, though others were of all ages illustrating different hatchings. There was an instinctive migration of these larvie of all sizes, and the strength of their food habits once acquired from birth upon a particular tree was well illustrated. At first the worms passed over various adjacent plants, like honeysuckles, roses, etc., the leaves of which they freely devour if “| wi Seh es 4 Pee ‘WHOM-AUM FHL AA GHLVIIOAAG SHH I—'] ALVIg Senet cA] SHADE TREES AND THEIR INSECT DEFOLIATORS OUR THE FALL WEB-WORM. 43 hatched upon them, but as the migrating swarm became pressed with hunger they finally fell upon these, and even upon plants like the Peach, and Ailanthus, which ordinarily are passed over. They would pounce upon any food, and a rotten apple placed in their way was soon literally swarming with them and sucked. dry. ‘In a general way it may be stated that conifers, grapes, and most herbaceous plants are free from their attacks, and it is very doubtful whether the species can mature upon them. “The list of plants which follows is arranged according to the relative damage to the foliage in the city of Washington. The three first named are most subject to attack, and, in fact, are almost always defoliated. PROPORTIONATE INJURY TO DIFFERENT PLANTS AND SHADE TREES, ‘¢The damage done in the city of Washington was exceptional, but so was also the general damage throughout the New England States, if not throughout the country. In New England the greater predilection which the species showed for Poplar, Cottonwood, and the ranker grow- ing Willows wasevery where manifest, and so much was this the case that the destruction of the first brood on these trees would have substan- tially lessened the damage to other trees.” Plants marked 1 have lost from 75 to 100 per cent. of their foliage. Plants marked 2 have lost from 50 to 75 per cent. of their foliage. Plants marked 3 have lost from 25 to 50 per cent. of their foliage. Plants marked 4 have lost from 0 to 25 per cent. of their foliage. Plants marked with two figures have shown the relative immunity or injury indicated by both, the variation being in individual trees. 1. Negundo aceroides Meench. (Box El- 2. Tilia americana L. (American Lin- der.) den.) 1. Populus alba L. (European White 2. Tilia europea L. (European Lin- Poplar. ) den. ) 1. Populus monilifera Aiton. (Cotton- 2. Populus dilatata Ait. (Lombardy wood.) : 5 Poplar.) 1-2. Populus balsamifera L. (Balsam 2. Ulmus americana L. (American Poplar.) White Elm.) 1-2. Populus tremuloides Mich’x. (Amer- | 2-3. Ulmus fulva Mich. (Slippery Elm.). can Aspen.) 2-3. Prunus armeniaca L. (Apricot.) 1-2. Fraxinus americana L. (White Ash.) | 2-3. Alnus maritima Muhl. (Alder. ) 1-2. Fraxinus excelsior L. (European | 2-3. Betula alba, L. (White Birch.) Ash.) | 2-3. Viburnum species. (Haw or Sloe.) 1-2. Sambucus canadensis L. (Elder.) | 2-3. Lonicera species. (Honeysuckles. ) 1-2. Pyrusspecies. (Cultivated Pearand 2-3. Prunus americana Marsh. (Wild Red Apple.) | Plum.) , 1-2. Prunus avium and cerasus L. (Cher- | 2-3. Celtis occidentalis L. (Hackberry.) ries. ) 2-3. Rosaspecies. (Rose. ) 1-4, Syringa vulgaris L. (Lilac.) 2-3. Gossypium album Ham. (Cotton.) 1-4. Ilex spec. (Holly.) 2-3. Cephalanthus occidentalis L. (Button 2. Platanus occidentalis L. (Sycamore.) | Bush. ) 2. Salix species, (Willow. ) 2-4. Convolvulus spec. (Morning Glory.) OUR SHADE TREES AND THEIR INSECT DEFOLIATORS. 2-4. Acer saccharinum Wang. (Sugar Maple.) 2-4, Geranium species. (Geranium.) 3. Betula nigra L. (Red Birch.) 3. Tecoma radicans Juss. (Trumpet Creeper. ) 3. Symphoricarpus racemosus. Mich’x. (Snowberry.) 3. Larix europea, Del. (European Larch.) 2. Corylus americana, Walt. (Hazel- . Quercus alba L. . Diospyros . Carya species. . Juglans species. . Wistaria sinensis Del. . Wistaria frutescens . Amelanchier . Crategus species. . Rubus species. . Spire@a species. . Ltibes species. . Staphylea trifolia L. . Cydonia vulgaris Pers. (Quince. ) . Asimina triloba Dun. . Berberis . Catalpa bignonioides Walt. . Catalpa speciosa Ward. 4, Euonymus atropurpureus Jaeg. (Burn- . Cornus alternifolia L. . Carpinus americana Mich’x. . Quercus . Quercus phellos L. nut. ) (White Oak.) virginiana L. (Persim- mon.) (Hickory. ) (Walnut.) teria. ) DC. (Native Wisteria. ) canadensis T. & G. (Shad-bush. ) (Haw.) (Blackberry. ) (Spirea.) (Currant and Goose- berry.) (Bladder Nut.) (Papaw.) canadensis Pursh. (Bar- berry.) (Indian bean.) (Bignonia.) ing Bush.) . Cupressus thyoides L. (White Cedar.) . Juniperus virginiana L. (Red Cedar.) . Cornus florida L. (Flowering Dog- wood.) (Alternate- leaved Dogwood.) j (Horn- beam. ) . Castanea americana Mich’x. (Ameri- can Chestnut.) ~ . Castanea pumila Mich’x. (Chinqua- pin. ) . Ostrya virginica Willd. (Hop Horn- beam.) coccinea Wang. (Scarlet Oak.) (Willow Oak.) (Chinese Wis- | 4 . Clematis species, . Trifolium spec. (Clover. ) . Helianthus spec. . Jasminum spec. . Rhus cotinus L. . Pinus spec. . Taxus spec. . Nyssa multifora Wangerh. . Fagus ferruginea Ait. . Liquidambar styraciflua L. . Quercus prinusL. (Chestnut Oak.) 3-4, Quercus rubra L. (Red Oak.) 3.4. Diospyros kaki L. (Japan Persim- mon. ) 3-4. Buxus sempervirens L. (Common Box.) 3-4. Hamamelis virginica L. (Witch Ha- i zel.) 3-4. Sassafras officinale Ness. (Sassafras.) 3-4. Cercis canadensis L. (Red Bud.) 3-4. Hibiscus syriacus L. (Tree Hibis- cus. ) 3-4. Rhamnus alnifolius L’Her. (Alder- leaved Buckthorn. ) 3-4. Prunus virginiana L. (Choke Cherry.) 3-4. Persica vulgaris Mill. (Peach. ) 3-4. dsculus hippocastanum L. (Horse Chestnut. ) 3-4. Paulownia imperialis Seeb. (Cigar Tree.) 3-4. Ailanthus glandulosus Daf. (Tree of Heaven.) 3-4. Maclura aurantiaca Nutt. (Osage Orange. ) 3-4. Ampelopsis quinquefolia. Virginia Creeper. ) (Clematis. ) (Sunflower. ) (Jesamine. ) (Fig.) (Smoke Tree.) (Pine. ) (Yew.) . Ficus carica L. (Sour Gum.) (Beech.) . Kalmia spec. (Laurel.) . hododendronspec. (Rhododendron. ) . Ricinus communis L. (Castor-oil Plant. ) (Sweet Gum. ) . Gleditschia triacanthos L. Locust. ) (Honey . Gymnocladus canadensis, Lamb. (Ken- tucky Coffee Tree.) . Robinia pseudacacia L. (Locust.) . Liriodendron tulipifera L. (Tulip ree.) . Magnolia spec. (Magnolia.) . Chionanthus virginicus L. (Fringe Tree. ) . Ligustrum vulgare L. (Privet.) THE FALL WEB-WORM. 4d 4, Zanthoxylum americanum M. (Prickly 4. Aisculus flava, Ait. (Sweet Buek- Ash. ) eye.) 4, Acer dasycarpum Ehrh. (White or 4. Asculus glabra Willd. (Ohio Buck- Silver Maple. ) “ eye.) 4. Acerrubrum Wangert. (Red Maple.) 4. Morus rubra L. (Red Mulberry.) ‘‘ Trees in the vicinity of the White Poplar and Cottonwood suffered most. Even trees usually notinjured, as, for instance, the Sugar Maple, are often badly defoliated when in such contiguity. “This list contains a number of plants not usually injured by these caterpillars. In some cases the injury was due to the fact that twigs con- taining the web, with its occupants, had been pruned from the tree and thrown near plants, instead of being at once burned or otherwise de- _ stroyed. ‘In other cases the injury is due to the peculiar position of the plant injured, 7. e., under a tree infested by the caterpillars. These when fully grown commence to scatter, and dropping upon the plants under- neath the tree so defoliate it without actually making their home upon it. The greatnumber thus dropping from a large tree will soon defoliate any smaller plant, even if each caterpillar takes but a mouthful by way of trial. Thus Holly, a plant not usually eaten by these insects, soon becomes denuded. Other plants unpalatable or even obnoxious to the caterpillars are sometimes destroyed by the multitudes in their seareh for more suitable food. ‘“‘Hungry caterpillars leaving a denuded tree in search of food wander in a straight line to the next tree, sometimes a distance of 25 feet, show- ing that they possess some keen sense to guide them. If such a tree offers unsuitable food, they still explore it for a long time before