// YMENOP TERA 941 



scribed it, the planidiuni, from the Greek meaning diminutive wanderer. The 

 planidea of the species of several genera have been described. Two of these, 

 Orasema viridis, described by Wheeler ('07a) and Psilogaster Jasciiventris de- 

 scribed by Brues ('19) are parasites of ants, and Perilampus hyalmus described by 

 H. S. Smith ('12) is a secondary parasite of the tachinid and ichneumonid para- 

 sites of the fall webworm. The planidium figured above was found by Miss 

 Norma Ford within the bodies of dissected specimens of one of the meadow- 

 grasshoppers, Conocephalns fasciatus; it is probably a secondary parasite of some 

 parasite of the grasshopper (Ford '22). 



The development of Perilampus hyalinus will serve as an illustration of the 

 life-cycle of these remarkable parasites. The egg has not been observed, but it 

 seems probable that it is deposited upon the food plant of the fall webworm in the 

 vicinity of a colony of this insect. The planidia, which measure less than 0.3 mm. 

 in length and are therefore almost invisible to the unaided eye, were found first on 

 the exterior of the caterpillars; later within their bodies, having bored through the 

 cuticula of the caterpillar by means of their well-developed mandibles; still later 

 the planidia were endoparasitic within the larvas of parasites of the caterpillars. 

 After feeding for a time the planidium molts; the second instar is ovate in shape, 

 with the head bent underneath. After another short period of feeding the larva 

 molts a second time and becomes greatly changed in form (Fig. 1168). Finally 

 after the primary parasite has left the caterpillar and pupated the larva of Peri- 

 lampus becomes an ectoparasite. It then soon completes its growth and pupates. 



Family CHALCIDID/E 



Many authors regard as distinct families the groups treated here 

 as subfamiUes. Since there is much difference of opinion regarding 

 the extent of the various groups and since the definition of many of 

 them is difficult, it seems unwise to call them families. The classi- 

 fication adopted is that of Ashmead ('04), except that the Leucospi- 

 dinas are separated from the Chalcidinse and that Ashmead 's families 

 are reduced to subfamilies. Some authors recognize additional 

 groups, among them the following: Eupelmidae, Tanaostigmatida;, 

 and Signiphoridae here included in the Encyrtinse; Leptofoenidas 

 ( = Pelecinellida') here included in the Cleonyminse ; Tridymidaj 

 included in the Miscogasterinfe; Spalangidae included in the Ptero- 

 malinae; and Aphelinidae, Elachertidag, Entedontidae, and Tetra- 

 stichidffi here included in the Eulophinaj. A thorough revision of 

 the genera and higher groups is greatly needed. Such a work would 

 do much to help the study of this difficult yet most interesting and 

 important family. 



The key to the subfamilies will serve for most species, though the 

 diversity of form in many groups and the present state of our knowl- 

 edge makes the construction of a reasonably perfect key quite difficult. 



KEY TO THE SUBFAMILIES OF CHALCIDID.^ 

 By Dr. H. K. Townes 



A. Tarsi with three segments; wing hairs usually arranged in lines; very small 



species, p. 949 Trichogrammatin^ 



AA. Tarsi with four or five segments. 



B. Hind wing linear; tarsus with four or five segments; minute species, p. 948 



Mymarin/E 



BB. Hind wing not linear, wider near the middle. 



C. Tarsi with four segments, or sometimes five-segmented; axilla of fore 

 wing produced on to mesonotum, its anterior margin on or in advance of 



