TNFL l EJS ' i: OF TE WPERA TUR ' \ $E( I - 49 



••In Kruman, in the Bohemian forests, have b< 

 counted, during a period of great increase of fir bark- 

 beetles in these foresl a L871 to L875, in a portion of 

 bark a square meter in extent, from 1400 t<> 4800 larv®" 

 (.1 udeich and Nitsch 



Influence of Changes of Temperature on Insect-life. — 

 Perhaps changes of temperature and unfavorable seasons 

 have, uexl to the increasing competition or struggle for 

 existence among insects, and the attacks of parasites, the 

 greatesl effect in maintaining the balance of nature, and 

 preventing the undue increase of destructive insecl Dr. 

 Shimer gives an accounl of an epidemic among the chinch- 

 bugs in Illinois, which "was at its maximum during the 

 moisl warm weather that followed the cold rains of June 

 and the first pari of July, 1865." Mr. ('. Thomas claims 

 that the high temperature of 1854, L871, and 1874, to- 

 gether with the diminished rainfall, furnishes the key to 

 the cause of the vast increase of chinch-bugs during those 

 years,* Wet weather is favorable and dry weather is un- 

 favorable to the increase of the cotton-worm. In timi 

 drought the eggs dry and fail to hatch, the worms are en- 

 feebled, " web up" prematurely, and die in attempting to 

 transform into the chrysalis state, and when the} suci 

 the chrysalides decay. " Nourishment and fecundity being 

 corr< lated, it is inure than probable that the moths, poorly 

 nourished, will lay fewer eggs under such circumstan 

 All the effects described are intensified and become most 

 marked during extreme drought, so that frequently at the 

 end of a dry spell, sinh as is not infrequent in duly and 

 early August, not a worm can be found. A rain} season, 



following such a spell, will produce a in iceahle 



change, "f 



The Bessian fly flourishes best in Be when the 



chinch-bug flourishes least. The hot, dry sumn - of 1881 



* Amer. Entomologist, iii. 241. 



t Riley, iu Fourth Report U. S. Entomological Cornmis 3 ; 



