198 HYMENOPTERA. 



pale honej^-yellow species, with a long club-shaped abdomen. 

 It lives in Cuba. 



Eogas is a genus differing from Bracon in having the three 

 first abdominal rings long, forming a slender petiole. 



In 3Iicrog aster, a genus containing numerous species, the 

 antennae are eighteen-jointed, and the abdomen is shorter than 

 usual, and clavate. There are two or three 

 subcostal cells, the second very small, 3Ii- 

 crogaster nephoptericis (Plate 3, figs. 3, 3 a) is 

 parasitic on Nephopteryx Edmandsii, found in 

 the cells of the Humble-bee. 



Aphidius, the parasite of the Plant-lice, is 

 a most valuable ally of man. It is known by 

 its small size, and by having the second and 

 third segments of the abdomen moving free on 

 Fig. 132. each other. There are three cubital cells, though 



the wings are sometimes wanting. Axjhklius (Praon) avena- 

 phis of Fitch, the Oat-louse Aphidius, is black with honey- 

 yellow legs, and is one-tenth of an inch long. Ap)hidius 

 (Toxares) triticapMs Fitch, the Wheat-louse Aphidius, is black, 

 shining, with thread-like antennae composed of twenty-five 

 joints. Its length is .08 inch. Frequently the large size of 

 the parasite causes the body of the dead Aphis to swell out 

 into a globular form. 



Proctotrypid^ (Proctotrupii) Latreille. Egg-parasites. 

 In this family are placed very minute species of parasitic Ich- 

 neumon-like Ilymenopters which have rather long and slender 

 bodies, with straight or elbowed antennae of various lengths, 

 often haired on the joints, usually ten to fifteen, sometimes only 

 eight in number, while the wings are covered with minute hairs 

 and most of the nervures are absent. The maxillary palpi are 

 three to six, the labial palpi usually three-jointed. The abdo- 

 men has from five to seven joints, and tlie tarsi arc mostly five- 

 jointed, rarely four-jointed. These insects are often so minute 

 that they can scarcely be distinguished by the naked eye unless 

 it is specially trained ; they are black or brown, and very 

 active in their habits. Thej^ may bo swept off" grass and 

 herbage, from aquatic plants, or from hot sand-banks. They 



