No. 22.] HYMENOPTERA OF CONNECTICUT. II 



Still other peculiarities will be noted under the different head- 

 ings to follow. 



The purpose of this treatise is primarily to present a ready 

 means for determining insects belonging to the Hymenoptera, 

 along with such cardinal facts as will leave no doubt as to the 

 desirability of becoming familiar with the order as a whole, and 

 more especially with those forms that are beneficial to us and the 

 few kinds that we call injurious. 



From the earliest times bees and wasps have aroused the 

 curiosity and interest of their observers, and even Virgil showed 

 in verse what he thought were the steps of development from 

 putrid bullocks to bees. Since those times increasing attention 

 has been given to these marvels of nature ; and, though they are 

 not yet receiving the investigation due them on account of their 

 relation to our welfare, and vast stores of economic knowledge 

 remain to be gathered by the scientist, enough has been learned 

 to convince any one of the utility of advancing our knowledge in 

 these paths of research. 



Ichneumon flies, Chalcis flies, and Serphus flies are of great 

 importance, because they are parasitic upon other insects, few 

 species being known to be exempt from their attack. Eggs of 

 dragon-flies, mantids, and many other insects are attacked, and 

 caterpillars, from the smallest to the largest and most formidable- 

 looking, as well as pupae. The tussock moth that devastates our 

 shade trees has at least seventeen kinds of these parasitic four- 

 winged flies attacking it and checking its ravages. Some idea of 

 the immense value of these natural checks can be gleaned from 

 contemplating the mathematically precise calculation made by 

 Professor Huxley on the prolific aphids or plant-lice which, 

 if it were not for the hymenopterous parasites and other agencies, 

 might destroy every green thing that grows. Professor Huxley 

 has shown that the tenth generation of the progeny of a single 

 aphis alone, exclusive of the preceding generations, would make 

 more substance than is contained in 500,000,000 stout men, each 

 man weighing about 280 pounds or 130 kilograms, or perhaps 

 more than is contained in the total population of China. 



The percentage of the individuals of the host affected by a 

 given parasite varies considerably, ranging from only a few per 

 cent, to as high as g?y 2 per cent., as shown by United States 



