022 AN INTRODUCTION TO ENTOMOLOGY 



long, common in the early spring. Most Braconinse parasitize cater- 

 pillars. 



The Macrocentrinse includes the genus Macrocentnis with about 

 forty species in North America. They are yellowish brown or more 

 or less black in color. They are slender with long legs and with 

 an ovipositor as long as the body. Caterpillars living in nests or in 

 tunnels are the usual hosts. Macrocentrus ancylkorus is a native 

 species first discovered parasitizing the strawberry leaf -roller {An- 

 cylis comptdna) in New Jersey. It has been found the most effective 

 control of the oriental fruit moth, a notorious pest of peaches, and 

 has now been colonized in peach orchards all over the eastern United 

 States and in some foreign countries. In some localities it parasitizes 

 more than eighty per cent of the fruit moth larvae. Macrocentrus 

 gifuensis is a polyembryonic species from the Old World introduced 

 a few years ago to help control the European corn borer. It is one 

 of the most effective parasites of this pest. 



The Alysiinae includes species with the teeth of the mandibles 

 pointing outward instead of inward toward the mouth. The only 

 other Hymenoptera with this type of mandible are the Vanhomiidce 

 and the ichneumonid genus Lysiognatha, very rare insects. The 

 Alysiinae are parasites of fly maggots, and the paddle-like mandibles 

 are used by some for digging in filth in search of hosts. 



The Aphidiinae includes delicate little species with a movable 

 joint between the second and third abdominal segments and with 

 reduced wing venation. All are parasites of plant lice. The female 

 aphidiine approaches an aphid and identifies it with a few taps of 

 her antennae. She then stands high and ducks her abdomen down 

 between her legs and forward in front of her head to plunge her 

 ovipositor into the plant louse. In a few days the developing parasite 

 larva has eaten out the inside of the aphid. It cuts a hole in the 

 bottom of the aphid's empty skin and through this glues the carcass 

 to the substratum. Then it makes its cocoon in the aphid's ab- 

 domen. The adult braconid emerges by cutting a 

 circular lid (Fig. 1151). In the genus Praon, the 

 cocoon is spun beneath instead of inside the host and 

 the dead aphid is used as a roof for the cocoon. Plant 

 lice with braconid cocoons inside have an inflated 

 appearance and brownish color that makes them 

 conspicuous among a colony of living aphids. These 

 ig- 1151- parasites are of prime importance in reducing the 



numbers of aphids and were it not for them, the lady beetles, the 

 lace-wing flies, and the syrphids, plant lice would be serious pests. 



Family ICHNEUMONID^* 



The Ichneumon Flies 



The Ichneumonidae includes most of the larger parasitic Hy- 

 menoptera. They are similar to the Braconidas and differ from most 



*The following papers should be consulted for identification of species: 



