248 NATURE STUDY AND LIFE 



unprotected on the leaves of plants ? The truth is that 

 nearly all of them have one or more species of ichneumon 

 fly ever seeking a victim in which to deposit her eggs. 

 So we shall find with nearly every species of larva we 

 attempt to rear that one of these parasitic flies has come 

 before us, and instead of the moth or butterfly we expected, 

 we get the brood of parasites. If we are intent on secur- 

 ing butterflies and moths, this is sometimes annoying; 

 but if we are studying insect life in the large, we are 

 thus often rewarded with a glimpse of one of its most 

 interesting and important phases. 



Simply ichneumons or, if that is not sufificient, ichneu- 

 mon wasps would be a better term by which to designate 

 this group, since they resemble wasps much more than 

 they do flies ; but they are described in all the books as 

 " ichneumon flies," and to change the name will take a 

 long time. Ichneumons are generally large or good-sized 

 parasitic insects, but some are minute. They have four 

 wings, like the bees and wasps, long, incessantly vibrating 

 antennae, and their prevailing color is dull yellow, though 

 many are black, marked with yellow. Our largest species 

 is the beautiful Thalessa atrata, which from the tip of 

 the antennae to the end of the ovipositor measures 

 nearly ten inches. It is parasitic on the larva of the 

 pigeon horntail, Tremex columba, a common borer in elms, 

 oaks, buttonwoods, and maples. Pimpla inquisitor, one 

 of the commonest and most widely distributed, ranging 

 from Massachusetts to California, is parasitic on a number 

 of caterpillars. The body is about half an inch long, shin- 

 ing black. The pupils are pretty certain to find it in 

 connection with their studies on the tent caterpillars and 



