78 



The Naturalist. 



before you, in the case upon the table, examples of ichneumons with 

 exserted and retracted organs of oviposition. 



It may naturally be asked, why should some Ichneumonida possess 

 such small and insignificant ovipositors, while others are burdened 

 with an instrument that looks as if it were nothing but an incumbrance 

 to the insect ? Those with a short terebra attack naked and exposed 

 larvse ; the others, with exserted ovipositors, are commissioned to hold 

 in check the ravages of wood boring and other concealed larv^. But 

 with so slender an instrument, how are they to reach mining larvae of 

 lignivorous and other habits ] It is to obviate this difficulty that the 

 two filamentous spiculas of the terebra are serrated at their tips. With 

 their aid, the ichneumon drills a hole in a tree trunk, where its instinct 

 tells it a fine fat grub is concealed, and safe as the little miner may 

 consider itself against the attacks of other predaceous insects, it speedily 

 finds that it is no match for an ichneumon, who with the gimlet 

 provided by nature, contrives to reach its concealed victim.^ 



I remember reading in some entomological work that hairy larvae 

 were seldom ichneumoned. I must say, that as far as my experience 

 goes, I have never found this to be the case. 



On May 2nd, of last year, I took a number of nearly full grown 

 larvae of that beautiful, yet common moth, Ghelonia coja. 



On the 30th of the same month, almost aU of them proved to be 

 ichneumoned, and the parasites that emerged (a species of Microgaster\ 

 had retracted ovipositors. 



Being curious to ascertain how, with so short an ovipositor, the 

 parasite could possibly pierce its victim, I took a larva of the moth, 

 and placed it in a glass-topped box. I then inserted an ichneumon, 

 which fortunately proved to be a female. At first it wandered about, 

 evidently without any ulterior aim, but presently came into contact 

 with the ends of the long hairs of the larva. The fly instantly vibrated 

 its long antennae with a rapid motion that meant business. By their 

 aid, the ichneumon carefully felt its way through the hairy labyrinth. 

 In this manner it approached within striking distance, and curving its 

 abdomen downwards, almost at a right angle, opened the sheath, 

 projected the terebra, and tried the spot. There was something or 

 other unsatisfactory, inasmuch as it closed the sheath, and repeated 

 the operation elsewhere. Once it nearly accomplished its purpose, but 

 suddenly started back and flew away. I am utterly at a loss to 

 account for this retrograde motion, which, however, was not peculiar to 

 the specimen, for others that I introduced did likewise. 



^ "Westw, Introduction to Class, of Insects, Vol. 2, Note to page 141, 



