POA” ta eyi9 Ope bedes A Ch yee aera ‘ ye kd lheh eae ro ke Dini eamin ; acne othe Pin Mattel eatin, oad OR arte HY sd - wm oer pecan b Historic, archived document Do not assume content reflects current scientific knowledge, policies, or practices. UNITED STATES DEPARTMENT OF AGRICULTURE BULLETIN No. 566 @ Contribution from the Bureau of Entomology L. O. HOWARD, Chief Washington, D. C. Vv June 18, 1917 THE EUROPEAN EARWIG' AND ITS CONTROL. By D. W. Jones, Scientific Assistant. CONTENTS. Page. Page. Description and seasonal history_____. 2 | Methods of dispersion_______________ 7 _ Disagreeable habits of concealment___. oulaNatural senemics# i222 Sere eS 7 5 | Control of the earwig_______________ 8 " PARC ME SLC Ge ee es ; The European earwig (fig. 1) was first noted at Newport, Re, in 1911 and is now present there in vast numbers. While it is not Fic. 1.—The European earwig (Forficula auricularia) : Adult males at left, adult females at right. (Original.) considered of great economic importance in Europe, it has increased so rapidly in Newport that it has become a serious pest and caused 1 Forficula auricularia L. Norr.—The first visit to Newport to study the habits of this insect was made by the writer in August, 1915. Hight trips of this kind, averaging four days each, were made }. during the summer and fall. Work was resumed May 6, 1916, and experiments were under close observation through the entire season. Mr. T. Suffern Tailer, a resident of Newport, whose grounds are in the heart of the area infested by this insect, gave finan- cial support to cover expenses of the control measures and furnished the writer a large room to be used as a laboratory. With his cooperation and the help of his head gar- _, dener, Mr. William Edward, many facilities for the study of this insect were provided. Cooperation was also secured from other owners and gardeners, and Mr. Perez Simmons, a graduate of the Massachusetts Agricultural College, assisted in the application of: con- trol measures. The photographs used were made by Mr. Harold A. Preston of the. Gipsy Moth Laboratory. 98190°_17 | 2 BULLETIN 566, U. S. DEPARTMENT OF AGRICULTURE. much annoyance. It is not unreasonable to suppose that this insect will spread to other sections of the country and cause great annoy- ance to farmers. A much smaller colony, which, however, has increased rapidly, was reported from Seattle, Wash., in 1915. Other reports of the occurrence of this earwig in the United States appear to have origi- nated from one or two cases in which isolated specimens were cap- tured on imported plants. This earwig is found all over Europe, but is seldom present in extreme numbers. It is impossible to say from which of the Euro- pean countries the colony at Newport originated, or how the first individuals were imported. Quantities of nursery stock arrive from abroad each year upon which the importation may have been made. DESCRIPTION AND SEASONAL HISTORY, THE EGG. The female earwig lays from 50 to 90 shining white eggs (fig. 2) in the ground, the eggs being about one-twentieth inch in length. Forty females were mated and placed in separate cans of soil for observation. One deposited 82 egos between November 6 and 10. On December 26 a second examination showed that 30 of the females (75 per cent) had deposited eggs. These females do not die at once, but hibernate, and in the spring attend the larve in their early stages. Mic. 2. Hess oF Ev During the previous year in a few cases eggs were pean earwig. n : F larged twice. deposited in the spring, but failed to hatch. Sear a Mellow garden soil with a southern exposure is a favorite place for egg deposition. Many hibernating females and their eggs have been found from 2 to 3 inches below the surface of the lawns. THE LARVA STAGES. The young earwigs, or larve, may be found in the ground, or at night on the soil surface, about May 5. They resemble the adults in general form, but have no wings and only delicate, simple forceps or pinchers on the posterior extremity of the body. At first they are pure white, but the color slowly darkens to a delicate olive green which has a peculiar shiny appearance. About June 9 they appear very dusky olive green, or even steel gray, with almost transparent 1The season during which these notes were gathered was rather peculiar. The entire spring was so cold and wet that foliage and insects were retarded in their development approximately one week. The summer was nearly normal, but was followed by a long dry fall. No killing frost occurred until the second week in November, and no real freezing of the soil took place until after December 1. The larval development in an ordinary season would be approximately one week ahead of the dates given for 1916, while the fall dates for hibernation and egg deposition usually would be from one to four weeks ahead of those in 1916. a Ce ee ee ee ae eee ST ee ae ne Oe ee ee eS ee ee eae Decl pe a male” a. 0S aie Ie THE EUROPEAN EARWIG AND ITS CONTROL. 3 legs and a dull-brown head (fig. 3). There are four larva stages which gradually approach the adult in size and color. The change from the fourth larva stage to the adult form takes place about July 18. When first hatched the larve leave their under- ground nests, most noticeably on warm nights about two hours after dark. They swarm over the ground, but usually stay within 2 or 3 feet of the entrance to their nest. On cold nights few can be found. As they grow older they are active even on cold, wet nights. = Young larve feed on very tender green shoots ee oe such as clover and grass, and possibly portions of — Enlarged twice. grass roots. Later they feed extensively on green = ‘O72!22)) shoots such as Lima-bean (fig. 4) or dahlia plants (fig. 5 in compari- son with fig. 6). By July 1 dahlia buds begin to appear and the blossoms of sweet William and early roses are plentiful. These are damaged greatly by the young earwigs. The bases of the petals and the stamens are eaten and the old taste for green shoots disappears if favorable flowers are near. Fig. 4.—Lima bean plant partially eaten by young earwigs. (Original. ) THE ADULT. The adult is rich reddish brown, with the wing covers and legs dull yellow brown, and the wings completely developed. From head 4 BULLETIN 566, U. S. DEPARTMENT OF AGRICULTURE. to tip of forceps it is about three-fourths of an inch in length. The forceps of the male are curved into a semicircle, or slightly elongated, with a tooth at the point of divergence. In the female the forceps are nearly straight. | The adults feed almost entirely on the petals and stamens of flow- | ers, although many other kinds of food, such as clover, grass, terminal buds of chrysanthemums, and other fall flowers, are eaten. They kill and eat certain unprotected, sluggish larvee, dead flies, and the dead or dying of their own species. In late summer the adults congregate in large numbers in crevices" or behind vines (fig. 7), near a good food supply. This concentration of large numbers of ear- wigs in favorable hiding places is due entirely to the mating instinct. HIBERNATION. Adult males seldom live over winter in Newport, R.I. Nearly all of them die after copulation, which oc- curs in the fall, before cold weather sets in. An occa- sional male is found in the ground with a female in the late fali; these males usu- ally die before spring. Aduit females hibernate in the ground from 2 to 8 inches below the surface. 2p Any well-drained soil is Fic. 5.—Dahlia plant defoliated by young earwigs. suitable, either in gardens penieuea or under the sod of the lawns. In some cases, as has been explained, they deposit eggs just before hibernating, so that this insect passes the winter in both the 7 i fe Ag and-eatat Stages: Emergence from hibernation is dependent on the temperature. In i6 females did not leave their hibernation quarters until the last week in April. No migration appears to occur in the spring, except individ- ual search for food. Apparently only a very. small percent- age of the total number of adult females is able to live over winter successfully. THE EUROPEAN EARWIG AND ITS CONTROL. : 5 DISAGREEABLE HABITS OF CONCEALMENT. The adult earwigs hide very quickly if disturbed by a sudden light or some unusual noise. During the day they hide in any crevice, fold of clothing, or even behind a convenient leaf which offers pro- tection. Thus one finds them in large numbers on the porches, behind the chair cushions, under the rugs, and in folds of awnings. On one estate, each morning when the porch awnings were let down, over a quart of earwigs dropped out and were swept up and burned. The writer has seen at least 300 adult earwigs in one of the servants’ halls at Newport. They were behind the cushions in the chairs, in Fig. 6.—Normal, uneaten dahlia plant. (Original.) folds of lace curtains, and even on the table. Bedrooms and bath- rooms of the finest houses may be invaded by occasional adults in spite of careful watchfulness and screens. They are decidedly repulsive when found crawling rapidly over the walls or furniture at night. The stories about bodily harm done by these insects are all without foundation. AREA INFESTED. The evidence at hand regarding the area infested previous to 1914 is very meager. It consists of data drawn from conversations with 6 * BULLETIN 566, U. S. DEPARTMENT OF AGRICULTURE. gardeners of the various estates. In almost every case they are men of education and trained powers of observation. 1911.—Mr. T. Suffern Tailer owns the estate where the first ear- wigs were noted. His gardener believes that a very few were present si SAE 1912.—Mr. Tailer and his gardener state definitely that earwigs were present in 1912. Specimens were sent to Washington, D. C., by Dr, A. E. Stene, of the Rhode Island State College. 1913.—The infestation in 1913 had spread to adjoining estates. Large numbers were found on Mr. Tailer’s estate and his men at- tempted certain control measures. Fic. 7.—A typical congregating place for adult earwigs. (Original.) 1914.—About -1 square mile was heavily infested in 1914. Mr. Richard Gardener, of Newport, wrote to the Bureau of Entomology at Washington, asking for information regarding the insect. 1915.—The infestation during 1915 was so heavy that letters re- questing information about methods of control were sent to Wash- ington and to the State college at Kingston, R. I. A careful scout- ing conducted by the writer showed that about 9 square miles were heavily infested. This area is bounded on three sides by water. On the fourth side, 2 miles of territory in addition to that infested in 1915 had small scattered colonies. One isolated colony was located | k i | | cath, rs, SR ae ee: a Ey ee ne Saks bet Sea THE EUROPEAN EARWIG AND ITS CONTROL. 7 about 64 miles northeast of this infested area, on the estate of the late Alfred Gwynn Vanderbilt, of Portsmouth. 1916.— About 10 square mle were heavily infested in 1916 and many new small colonies were found outside of this area. The small colonies of the previous year showed considerable growth. In some cases hundreds of earwigs were present on estates where only a few were found the year before. _ METHODS OF DISPERSION. This species rarely if ever spreads by flight; in fact, experi- mental efforts to induce these insects to use their delicate and com- plex wings were unsuccessful. Many cases have been noticed where adult earwigs have been carried long distances in folds of clothing. Visitors to Newport may spread the insect to near-by cities in this way. Several isolated colonies located at a distance from the main infestation are at points where automobiles frequently stop while their owners walk about the extensive grounds. These insects may be spread while hiding in the packing mate- rial or the soil of shipments of plants and general nursery stock. One dead specimen was found by J. J. Pillsbury, assistant State entomologist of Rhode Island, in a shipment of plants from Holland. The writer has noted these insects in the fall between the toes of dahlia bulbs. : NATURAL ENEMIES. A parasitic, threadlike worm has caused the death of approxi- mately 10 per cent of the earwig larve under close observation in the laboratory. This worm? lives free in the body cavity of full- grown larval and adult earwigs. The average measurements of five of these parasites was 34 inches by 4 inch. Various other parasites are reported as having been reared from this species of earwig in Europe, but at Newport those so far dis- sected have been free from parasites except in the case of one small unidentified larva and the worm just referred to. Toads eat earwig larvee readily, but are not common at Newport. Hens devour adult earwigs ravenously. One hen ate 10 of these insects thrown to her in as many seconds. Under natural conditions these insects are hidden away so earefully through the day that fowls can hardly be considered as economically important in the sense of controlling the insect. 1 Filaria locustae. 8 BULLETIN 566, U. S. DEPARTMENT OF AGRICULTURE. CONTROL OF THE EARWIG. NEED FOR SPECIAL CONTROL MEASURES. In Europe this insect appears to be held in check by parasites and other natural agencies, and it is very rarely present in large numbers. Gardeners who raise prize dahlias, chrysanthemums, and flowers of that class are the only ones who consider the earwig an actual pest. As a result control measures have developed slowly. Their aim has been simply to protect a small area from the depredations of a comparatively small number of earwigs. Various methods of trap- ping have been developed which satisfy the need, so no better methods have been worked out. At Newport, as has been stated, this insect occurs in vast numbers. The lack of parasites and other natural enemies, together with the favorable conditions met with at every stage of the life history, has made this rapid increase possible. The control measures offered in this paper have been developed through laboratory tests and later have been tested in field trials on a large scale. POISONED BAIT. For early spring control, May 15 to June 15, poisoned-bread bait has proved extremely effective. In fact, it gave far better results than any other mixture that was tried. This method would prove cumbersome and expensive for the average farmer, but its extreme effectiveness makes it the best to recommend at this time. Stale bread was secured in 1916 for approximately 2 cents per pound. The bait is prepared as follows: | Stale “white. breads" es. ae ee ps ee pounds__ 16 Paris! . SPOGT S22 cece TAS a a Se A pound=— i Water. Grind the bread up fine in a meat-chopping machine and mix the Paris green with it while dry. Stir the mixture thoroughly, slowly adding water enough to make a mixture which will run through the fingers, and one which, when thrown broadcast with some force, will break up into small particles. The addition of cheap honey to the mixture increases its effectiveness, but is not necessary. This bait should be spread broadcast between dusk and 9 p. m. in gardens and on lawns near vines and shrubs. It should be thrown with considerable force in order to break the bait up into smaller pieces. If the infestation is heavy or was heavy the previous year, three applications covering about 10 days may be necessary. Warm evenings should be selected if possible, as on such nights the larvee are more active. ——e THE EUROPEAN EARWIG AND ITS CONTROL. 9 SONG BIRDS AND THE POISONED-BREAD BAIT. The danger to song birds from the poisoned bread is very shght in the spring. After the 1st of July, especially in dry seasons when worms are not plentiful, this danger probably would increase. On May 11 an attempt was made to see if song birds would feed on this poisoned-bread bait. A narrow, recently spaded garden was selected which was south of a small greenhouse and east of a high privet hedge, where various birds were plentiful. Bits of this poisoned bait, the size of a pea, were placed 2 feet apart and 4 inches from the grass border, around the entire edge of the garden. The next morn- ing the writer seated himself inside the greenhouse before daylight and watched the birds from 3.15 until 5.45 a.m. Ten robins were noted hopping along parallel to or crossing the lines of bait. 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