2 PROCEEDINGS OF THE NATIONAL MUSEUM. vol. 63. 



all measurements. The figures of the antennae in the genus Leptacis 

 were made by the author from sketches prepared by Miss Eleanor 

 Armstrong, an artist in the employ of the Department of Agriculture. 

 The other drawings were made by the author. 



The manuscript for this paper was completed in the autumn of 1921 

 and it has been inadvisable to bring the bibliography of all the species 

 up to date. All of the necessary references to the classification have, 

 however, been added. 



PREPARATION. 



No special preparation in mounting is necessary with these insects. 

 They are hard and almost indestructible if ordinary precautions are 

 taken. The best way of mounting is to fasten them with shellac to 

 the tips of card points. One specimen should be attached to a point, 

 the latter to be pierced at its broader end by an insect pin. By this 

 means specimens may be preserved indefinitely. There are some so 

 mounted in the National Collection which, although collected many 

 years ago, are still in perfect condition. 



It is not advisable to mount the entire specimen on a slide. This 

 may be done with advantage in the case of certain Chalcids but not 

 here. One should, however, mount the antennae in balsam on a slide. 

 In several genera {Plaiygaster, Leptacis) the structure of the antennae 

 is of importance in classification. 



ACKNOWLEDGMENTS. 



The writer is indebted to Mr. S. A. Rohwer, custodian of Hymenop- 

 tera, for encouragement and numerous useful suggestions. He has 

 also helped in the general arrangement of the work. 



Subfamily Platygasterinae. 



Characters. — Wings veinless; mandibles bidentate; antenna niue 

 or ten jointed, frequently clavate in the female; abdomen petiolate, 

 carinate laterally, composed of six segments in the female and of 

 seven in the male; legs slender, pubescent, with five-jointed tarsi. 



The group may be easily recognized by the use of the diagnosis 

 just given. No other group in the Order Hymenoptera has veinless 

 wings. 



All of the species are small, none that I have seen being over 4 

 millimeters in length. Records show that nearly all reared forms 

 are parasitic on the flies of the Family Itonidae. Records of differ- 

 ent rearings are in every case doubtful. (See description of Amitus 

 aleurodinis Haldeman.) 



