172 



THE AMERICAN ENTOMOLOGIST. 



even foui--brooded. For instance, the moth 

 known as the Poplar Spinner, (Clostera ameri- 

 cana, Harris), is stated by Dr. Harris and Dr. 

 Fitch to be only single-brooded in Massachusetts 

 and New York, the insect spinning up in Sep- 

 tember or October, passing the winter in the 

 pupa state, and coming out in the winged form 

 iu the following June. But Dr. Harris — no 

 doubt on the authority of Abbott — states that 

 "in Georgia this insect breeds twice a year;"* 

 and we ourselves reared numerous specimens 

 of the moth, July 19th and subsequently, from 

 larviB obtained at Champaign in Central Illinois 

 at the beginning of the same month of the same 

 year. Wlieuce it necessarily follows, that in 

 Central Illinois, as well as in Georgia, this spe- 

 cies must be double-brooded ; for otherwise the 

 majority, at all events, of our larva; would have 

 remained in their cocoons till the following 

 spring; whereas every cocoon that we obtained 

 produced a moth the same season, and iu ample 

 time for a second brood of caterpillars to ma- 

 ture from the eggs laid by this brood of moths. 

 If, therefore, the Poplar Spinner can be single- 

 brooded iu Massachusetts and New York, and 

 double-brooded in Central Illinois and in Geor- 

 gia, it is quite reasonable to infer that an insect 

 such as the Chinch Bug, which in North Illinois 

 is only allowed by the shortness of the summer 

 to mature two broods, may be enabled in re- 

 gions where tlie summer is so much longer to 

 mature three or possibly even four broods. 



It is these two peculiarities in the habits of 

 the Chinch Bug, namely, first, its continuing to 

 take food from the day of its birth to the day of 

 its death, and secondly its being eitlier two- 

 brooded or many-brooded, that renders it so 

 destructive and so difficult to combat. vSuch as 

 survive the autumn, when the plants on the sap 

 of which they feed are mostly dried up so as to 

 afford them little or no nourishment, pass the 

 winter in the usual torpid state, and always in 

 the perfect or winged form, under dead leaves, 

 under sticks of wood, under flat stones, in moss, 

 in bunches of old dead grass or weeds or straw, 

 and often in corn-stalks and corn-shucks. In 

 the winter all kinds of insect-devouring 

 animals, such as birds, shrew-mice, etc., are 

 hard put to it for food, and have to search every 

 hole and corner for their appropriate prey. But 

 no matter how closely they may thin out the 

 Cliinch Bugs, or how generally these insects 

 may have been starved out by the autumnal 

 droughts, there will always be a few left for 

 seed next year. Suppose that there are only 

 2,000 Chinch Bugs remaining in the spring 



*Injuriou» Insects, \i. 434 



in a certain field, and that each female of the 

 2,000, as vegetation starts, raises a family of only 

 200, which is a low calculation. Then — allow- 

 ing the sexes to be equal in number, whereas in 

 reality the females are always far more numer- 

 ous than the males — the first or spring brood 

 will consist of 200,000, of which number 100,000 

 will be females. Here, if the species were single- 

 brooded, the process would stop for the current 

 year; and 200,000 Chinch Bugs in one field 

 would be thought nothing of by the AVestern 

 farmer. But the species is not single-brooded 

 and the process does not stop here. Each 

 successive brood increases in numbers in Geo- 

 metrical Progression, unless there be something 

 to check their increase; until the second brood 

 amounts to tv/enty millions, and the third brood 

 to two thousand millions. We may form some 

 idea of the meaning of two thousand millions 

 of Chinch Bugs, when it is stated that that 

 number of Lheni, placed in a straight line head 

 and tail together, would just about reach from 

 the surface of the earth to its central point — a 

 distance of four thousand miles. 



Dr. Shimer states that "on May IG, 1865, a 

 bright, sunny, summer-like day, the atmosphere 

 was swarming with Chinch Bugs on the wing 

 at Mt. Carroll, in North Illinois." "They were 

 so numerous," he adds, " alighting on the pave- 

 ments in the village, that scarcely a step could 

 be taken without crushing many of them under 

 foot. In a few days they had all disappeared." 

 He had, as he tells us, witnessed the same 

 phenomenon in their "autumnal love-season" 

 in the year 18C1, and again in the year 18C4 ; and 

 it appears from the context that by " autumnal " 

 he means a period in the year at least as early 

 as August.* In the course of an entomological 

 experience of eleven years in North Illinois, we 

 have ourselves witnessed one such fiight of 

 Chinch Bugs— not however by any means as 

 copious a one as that described by Dr. Shimer — 

 and this occurred near Rock Island on July 

 26lli, 18C4. Dr. Shimer deduces from the facts 

 observed by liini what seems to us rather a 

 strained inference, namely, that it is the normal 

 habit of these insects to take wing in vast 

 droves every spring and summer, or as he would 

 call it " autumn ; " that these occasions form 

 their only "love-seasons;" and that "these 

 remarkable little creatures prefer to conduct 

 their courtshii)s under the searching gaze of the 

 noonday sun." If his theory were correct, and 

 Chinch Bugs regularly took wing in North Illi- 

 nois iu vast swarms twice every year, it seems 



•Sep Dr. Shimev's I'aiier in Trans. N 111 II.>rl. Soc. Rmt 

 compm-e pages 98 and 99 



