10 PROCEEDINGS OF THE NATIONAL MUSEUM. vol.63. 



Type locality. — Illinois. 



Type. — In collection of American Entomological Society. 

 Other localities. — Pennsylvania and District of Columbia. 

 Redescribed from a series of specimens in the National Museum 

 labeled, "Par. on Aleurodes on Maple leaves; issued Feb. 6, 1874." 

 I quote Professor Haldeman on the habits of the species: 



Parasitic on the larva of Aleurodes corni Hald., of which it destroys a great many. 

 I found it with that insect beneath the leaves of Cornus sericea on the margin of a 

 water course. It leaps, walks, and flies with facility, and when touched simulates 

 death. I have kept them a week or more, living in confinement. The ova (crushed 

 from the ovaries; are fusiform, rounded at one extremity and produced at the other 

 like the neck of a flask. 



IV. Genus ISORHOMBUS Foerster. 



Isorhombus Foerster, Hym. Stud., Heft 2, 1856, pp. 107, 113. No species 

 originally included. 



Vertex seen from in front highly elevated; that part of the head 

 bounded by a line drawn from the middle point of the vertex to the 

 outer margins of the eyes and from thence to the mouth forming a 

 perfect diamond-shaped figure ; occiput not separated from the ver- 

 tex by a sharp carina; antennal club in female three- jointed. Genus 

 in other respects similar to Leptacis. 



I have seen no specimens referable to this genus. The two species 

 included by Ashmead^ belong to other genera in the subfamily. 

 /. hyalinipeiinis Ashmead is referred to Platygaster and arizonensis 

 Ashmead to TricJiacis. 



V. Genus ISOCYBUS Foerster. 



Isocybus Foerster, Hym. Stud., Heft. 2, 1856, p. 114. Four species. 

 Genotype. — (Platygaster ruficornis Walker) = Platygaster grandis Nees. By 

 original designation. 



This genus is closely related to Platygaster Latreille and TricJiacis 

 Foerster. It may be separated from the former only by the shape 

 of the head, which is more or less cubical, very full behind and 

 above the eyes. As in TricJiacis the scutellum is of an irregular 

 shape, never Smoothly rounded above and evenly sculptured, and 

 has a more or less distinct tuft of hair above. In Platygaster the 

 pubescence is scattered and always denser on the sides than on the 

 top. The abdomen is six segmented in the female and seven in the 

 male. The second tergite is not densely pubescent proximally and 

 has two basal foveae. 



Foerster 2 designated as type the species described by Walker' 

 under the name Platygaster ruficornis Latreille. P. ruficornis 



iBuU. 45, U. S. Nat. Mus., 1893, pp. 276 and 277. 

 »Hym. Stud., Heft. 2, 1856, p. 114. 

 •Ent. Mag., vol. 3, 1835, p. 240. 



