HYMENOPTERA 949 



cyclopoid, resembling that of the SceHonidce. As many as fifty para- 

 sites have been reared from a single egg, although one is the usual 



Fig. 1 169. — Cosmocoma elegans. 



Subfamily TRICHOGRAMMATIN^ 



This subfamily comprises minute egg parasites with three-seg- 

 mented tarsi. Trichogramma evanescens ( = minuttmi) is an ubiquitous 

 species parasitizing almost any insect egg that can be pierced with 

 its ovipositor. It is an important parasite of many economic pests 

 and has frequently been reared in insectaries for liberation in fields 

 and orchards to control various insects. The success of these at- 

 tempts has not been encouraging. Several other forms of Tricho- 

 gramma resemble T. evanescens very closely, differing somewhat in 

 color and in length of the life cycle when reared at a constant tem- 

 perature. Since they will not interbreed with T. evanescens they are 

 now regarded as distinct species. Hydrophylax aquivolans is an 

 aquatic species parasitic probably upon damsel fly eggs. It has 

 narrow wings and uses them as oars for "flying" through the water. 

 Some species of Trichogrammatinae have two larval instars, the first 

 of cyclopoid form as in the Mymarinse and Scelionidas. Others have a 

 single instar, a bag of cells with a mouth. This larva gets the egg 

 contents on the inside of its body and then pupates. 



SUPERFAMILY EVANIOIDEA 

 Family EVANIIDiE 

 The Ensign-flies 



The family Evaniidae is so distinctly separated from all other 

 famihes of the Hymenoptera that it is regarded as constituting a 

 separate superfamily. We have in this case a superfamily represented 

 by a single family. 



The family Evaniidae dift'ers from all of the preceding families in 

 the presence of a well-marked anal lobe in the hind wings (Fig. 1 170) 

 and it differs from all of the following families in that the petiole of 



