THE A]\IERICAN ENTOMOLOGIST. 



171 



the "West in very small numbers, but that it was 

 for a long time prevented by certain causes from 

 multiplying to the injurious extent that it now 

 does. At all events, we know from the evi- 

 dence of Dr. Harris and Dr. Fitch, that it existed 

 long ago in exceedingly small numbers in New 

 York, and even in Massachusetts. What the 

 causes may have been, that thinned out the 

 ntimbers of this insect in former times in the 

 West, is another question. AVe strongly suspect 

 that, in former times, the great bulk of these 

 bugs were destroyed every winter by the prairie 

 fires, and that, as cultivation has extended in 

 consequence of the country being gradually 

 settled up, and less and less prairie has been 

 annually burnt over, the inimber that has sur- 

 vived through the winter to start tlie next year's 

 broods has annually become greater. If these 

 views be correct, we may expect them, unless 

 more jiains be taken to counterwork and de- 

 stroy them, to become, on the average of years, 

 slill more abundant than they now are, when- 

 ever prairic-tires shall have become an obsolete 

 institution; until at last Western farmers will 

 be compelled, as those of North Carolina have 

 already several times been compelled, to quit 

 growing wheat altogether for a term of years. 



It may be very reasonably asked, why the 

 t'hiuch Bug does not increase and multiply in 

 Massachusetts and New York, seeing that it 

 existed there long ago, and that there are, of 

 course, no prairie-lires in those States to keep it 

 in check. The answer is, that the Chinch Bug 

 is a Southern, not a Northern species; and that 

 hundreds of Southern species of insects, which 

 on the Atlantic seaboard only occur in southerly 

 latitudes, are found in profusion in quite a high 

 latitude in the Valley of the Mississippi. The 

 same law, as has been observed by Prof. Baird 

 holds good both with Birds and with Fishes.* 



Natural History of the CLiuch Bag. 

 In the four great and extensive Orders of In- 

 sects, namely, the Beetles {Coleoptera), the 

 Clear-winged Flies (Ili/nienoptera) , the Scaly- 

 winged Flies (Lepidoptera) , and the Two- 

 winged Flics (Diptem), and in one of the four 

 small Orders in its restricted sense, namely, the 

 Net-winged Flies {Xeuroptera), the insect 

 usually lies still throughout the pupa state, 

 and is always so far from being able to 

 eat or to evacuate, that both mouth and 

 anus are closed up liy membrane. In the 

 remaining three small Orders, on the 

 contrary, namely, that of the Straight- 



' SiUiman's Journal, XLI, p. S7. 



winged Flies in its most extensive sense (Or- 

 thoptera including Pseudo-neuroptera) , the 

 Ilalf-winged Bugs (^llel.eroptera) and the 

 Whole- winged Bugs (//o?iioj3^er«), the pupa is 

 Just as active and just as ravenous as either the 

 larva or the perfect insect, and the little crea- 

 ture never quits eating as long as the warm 

 weather lasts, except for a day or so while 

 it is accomplishing each of its successive three, 

 four or five moults. As the Chinch Bug belongs 

 to the Half-winged Bugs, it therefore continues 

 to take food, with a few short intermissions, 

 from tlie day when it hatches out from the egg 

 to the day of its unlamented death. 



Most insects — irrespective of the Order to 

 which they belong — require 12 months to go 

 through the complete circle of their changes, 

 from the day that the egg is laid to the day 

 when the perfect insect perishes of old age and 

 decrepitude. A few require 3 years, as for 

 example the Round-headed Apple-tree Borer 

 {Saperda biviltata, Say) and the White Grub 

 which produces the May-bug {La chno sterna 

 quercina, Knoch.) One species, the Thirteen- 

 year Locust {Cicada tredecim, Riley), actually 

 requires 13 years to pass from the egg to the 

 winged state ; and another, the Seventeen-year 

 Locust {Cicada septemdecim, Linn.), the still 

 longer period of 17 years. On the other hand 

 tliere are not a few that pass through all their 

 tliree states in a few months, or even in a few 

 weeks: so that in one and the same year there 

 may be 2, 3 or even 4 or .5 broods, one generated 

 by the other and one succeeding another. For 

 example, the Hessian Fly {Cecidomyia destruc- 

 tor, Say), the common Slug-worm of the Pear 

 {Selandria cerasi, I'eck), the Slug-worm of the 

 Rose {Selandria rosce, Harris), the Apple-worm 

 and a few others, jiroduce exactly two genei-a- 

 tions in one year, and hence may be termed 

 "two-brooded." Again, the Colorado Potato- 

 bug in North Illinois is three-brooded, and not 

 improbably in more southerly regions is four- 

 brooded. L.astly, the common House-fly, the 

 Cheese-fly, the various species of Blow-flies 

 and Meat-flies, and the multifarious species of 

 Plant-lice {Aphis) produce an indefinite num- 

 ber of successive broods in a single year, some- 

 times amounting in the case of the last-named 

 genus, as has been proved by actual experi- 

 ment, to as many as nine. So far as regards the 

 Chinch Bug, we know from the very valuable 

 and pains-taking observations of Dr. II. Shimer, 

 that in North Illinois it produces just two gen- 

 erations or broods in one year. But it is quite 

 agreeable to analogy, that iu more southerly 

 latitudes it may be three-brooded or possibly 



