THE AMERICAN ENTOMOLOGIST. 



171 



the West in very small numbers, but that it was 

 for a longtime 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 

 numbers of this insect in former times in the 

 West, is another question. We 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 number that has sur- 

 vived through the winter to start the next year's 

 broods has annually become greater. If these 

 views be correct, we may expect them, unless 

 more pains be taken to counterwork and de- 

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

 still more abundant than they now are, when- 

 ever prairie-fires shall have become an obsolete 

 institution; until at last AVesteni 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 

 CJIiinch Bug does not increase and multiply in 

 Massachusetts and Now York, seeing that it 

 existed there long ago, and that there are, of 

 course, no prairie-fires 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 iu the Valley of the Mississijipi. The 

 same law, as has been observed by Prof. Baird 

 holds good both with Birds and with Fishes.* 



Natural History of llic Cliiiieli liag. 



lu the four great and extensive Orders of In- 

 sects, namely, the Beetles {Coleoptera) , the 

 Clear-winged Flies {Hymenoptera) , the Scaly- 

 wiuged Flies (Lejndoptera) , and the Two- 

 winged Flies (Biptera), and iu one of the four 

 small Orders in its restricted sense, namely, the 

 Net-winged Flies {Neuropteru), the insect 

 usually lies still throughout the pupa state, 

 aud is always so far from being able to 

 eat or to evacuate, that both mouth and 

 anus arc closed up by membrane. In the 

 remaining three small Orders, on the 

 contrary, namely, that of the Straight- 



* Silliinan's Journal, XLI, p. S7. 



winged Flies in its most extensive sense (Or- 

 ihoptera including Pseudo-neuropitera) , the 

 Half-winged Bugs {HeUroptera) and the 

 Whole-winged Bugs (//ojnojs^era), 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 the day when it hatches out from the ^gg 

 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 hiviltata, Say) and the White Grub ^ 

 which produces the May-bug (Laclinosterna ^ 

 qnei'cina. Knoeh.) One species, the Thirteen- 

 year Locust (Cicada tredeeim, 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 

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

 weeks ; so that iu one aud the same year there 

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

 by the other and one succeeding another. For l 

 example, the Hessian Fly (Cecidomyia destruc- 

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

 (Selandria cerasi, Peck), the Slug-worm of the 

 Rose (Selandria rosm, Harris), the Apple-worm ,^ 

 aud a few others, produce exactly two genera- 

 tions in one year, and hence nniy be termed 

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

 bug iu North Illinois is three-brooded, and not 

 improbably iu more southerly regions is four- 

 brooded. Lastly, 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 amouuting 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 in more southerly 

 latitudes it may be three-brooded or possibly 



