HYMENOPTERA 



347 



interest these little braconids ovipositing in. the bodies of plant-lice. 

 When one has selected a plant-louse in which to oviposit she stands with 

 her head toward it, and bending her abdomen under her thorax between 

 her legs she darts her ovipositor forward into the body of the aphid. The 

 species of this genus do not construct cocoons, but undergo their meta- 

 morphosis within the dried skins of plant-lice. 



Family Ichneumonid^; 

 The Ichneumon -flies 



This is a large family including a great number of genera and species. 

 Although it includes some minute forms the species are mostly of con- 

 siderable size, and here belong the larger of the parasitic Hymenoptera. 



In this family, as in the 

 preceding one, the costal 

 cell of the fore wings has 

 been eliminated by the coa- 

 lescence of veins and the 

 venter is usually membra- 

 nous and has in dried speci- 

 mens a longitudinal fold 



(Fig. 587)- 



Students collecting Hy- 

 menoptera will find many 

 species of ichneumon-flies; 

 and those attempting to 

 rear caterpillars will be dis- FlG ' s87 ' ~ Win?s of an Ichneumon Ay- 



appointed often by the breeding of ichneumon-flies instead of moths or 



butterflies. 



Megarhyssa lunator, which was 

 formerly known as Thalcssa lunator, 

 is one of the larger of ichneumon- 

 flies (Fig. 588). It is a parasite of 

 the wood-boring larva of the pigeon 

 horn-tail, Tremex columba. When a 

 female finds a tree infested by this 

 borer she selects a place which she 

 judges is opposite a Tremex-burrow, 

 and elevating her long ovipositor in 

 a loop over her back, with its tip on 

 the bark of the tree (Fig. 588), she 

 makes a derrick out of her body 

 and proceeds with great skill and 

 precision to drill a hole into the 

 tree. When the Tremex-burrow is 

 reached she deposits an egg in it. 

 The larva that hatches from this egg 

 creeps along this burrow until it 

 reaches its victim, and then fastens itself to the horn-tail larva, which it 

 destroys by sucking its blood. The larva of Megarhyssa when full-grown 

 changes to a pupa within the burrow of its host, and the adult gnaws a 



Fig. 588. — Megarhyssa lunator. 



