930 



AN INTRODUCTION TO ENTOMOLOGY 



ha\'inj? the fore wings folded when at rest and in never having the 

 ovipositor curved forward over the dorsiun. In these two subfamilies 

 are found the largest of our chalcid-flies. Most of the species of the 

 Chalcidina) are parasitic on lepidopterous larvae or pupae; a few are 

 parasitic on other insects. 



Subfamily APHELININ^ 



This subfamily is composed of small species that are parasitic 

 upon coccids, aphids and aleyrodids; it includes the most important 

 parasites of the Diaspinae. For a table of genera and figures, and 

 descriptions of many species see Howard ('95 and '07). 



Subfamily MYMARIN^ 



To this subfamily belong some of the smallest of insects. All of 

 the species so far as is known are parasites in the eggs of other insects. 



In this family the hind 

 wings are linear and pe- 

 dunculate at the base 

 (Fig. 1 169). 



Subfamily 

 EURYTOMIN^ 



Fig. 1169. — Cosmocoma elegans. 



This subfamily is re- 

 markable on account of 

 the diversity of habits 

 among the various groups 

 of genera composing it. 

 Some, like most other 

 chalcid-fiies, are parasit- 

 ic ; among these are those 

 that infest the nests of bees and wasps ; other that are parasitic upon 

 gall-making H^inenoptera and Diptera ; some that are parasitic upon 

 Coleoptera and other insects; and a few that destroy the eggs of 

 orthopterous insects. In addition to this diversity of parasitic habits 

 is the anomalous fact that certain genera are phytophagous; among 

 the more important of these are the following. 



The grass and grain joint-worm flies, //armo/i/a {=Isosdnia). — The 

 members of this genus infest the stalks of growing grasses and grains, 

 often causing the formation of gall-like swellings at or just above the 

 first joint, hence the common name joint-worm flies. The two follow- 

 ing species are of considerable economic importance. 



The wheat joint-worm, Harmoltta trttici. — This is a well-known 

 pest which infests the stalks of growing wheat and certain grasses. 

 It causes a woody growth which fills up the cavity of the stalk, and 

 sometimes also causes a joint to swell and the stalk to bend and lop 

 down. The presence of this insect is often indicated by pieces of 



