948 ^A^ INTRODUCTION TO ENTOMOLOGY 



Euplectnis platyhypence is a common parasite of army worms. It 

 is unusual in being an external parasite of an exposed host. The 

 eggs are deposited on the caterpillar's skin in groups of about twenty 

 to thirty. The larvse form a compact mass with the heads attached 

 to feeding holes in the skin of the host. The caterpillar does not die 

 until they become mature and detach from their feeding holes. The 

 parasites pupate under the dead host. 



Melittdhia is common in the nests of solitary bees and wasps. 

 The female gains access to the larval cell, stings the enclosed larva 

 or pupa to paralyze it and then deposits her eggs on it. The parasite 

 larvtc develop externally. Several generations develop on the same 

 host before it is completely consumed. The males are short-winged 

 and have the antenna modified into a pincher-like structure for hold- 

 ing the female's antenna during courtship. They are very pug- 

 nacious and often kill each other in battle. The females are either 

 short- or long-winged. 



Tetrastich us is a large important genus parasitic on many kinds 

 of insects. T. aspdragi oviposits in the eggs of the asparagus beetle. 

 The beetle egg hatches and the larva lives to maturity but is killed 

 in its pupal cell by its parasites. About a half dozen parasite larvae 

 develop in each host. 



A large and important group of Eulophin^, sometimes put in the 

 separate subfamily Aphelininse, are parasites of scale insects. A few 

 attack aphids and aleyrodids. Several species of this group have 

 been introduced into various countries to control certain species of 

 scale insects and have proved remarkably efficient. In some species 

 of Coccophagus and related genera the male and female larvae are 

 strikingly different in morphology and in habits. The male and 

 female eggs also are different. The female larva develops as a primary 

 parasite of a scale insect while the male larva is a secondary parasite 

 in the scale, either upon a female larva of its own species or on some 

 other chalcid. For a revision of Coccophagus see Compere: Proc. 

 U. S. Nat. Mus. 1931, vol. 78, art. 7, 132 pages. 



Subfamily ELASMIN^ 



Eldsmus is the only North American genus of the Elasminas. It 

 contains small black or brown species somewhat triangular in cross 

 section. Most species are solitary or gregarious external parasites of 

 caterpillars. 



Subfamily MYMARIN^ 



The Fairy-flies 



The Mymarinas includes exceedingly minute species parasitic in 

 the eggs of other insects. They may be recognized by the linear hind 

 wings pedunculate at the base (Fig. 11 69). Species of the genus Al- 

 Idptus are some of the smallest insects known. One has a body length 

 of only 0.21 millimeters. The entire development of the Mymarinai 

 is in the host egg. There are two larval instars of which the first is 



