THE CHALCIDOID GENUS PEEILAMPUS. 59 



PLANIDIUM OF ORASEMA VIRIDIS ASHMEAD. 



Length about 0.16 mm. General shaj^e like that of Perilamjms, 

 but comparatively broader and much more simple in structural 

 detail. Color dark, as in Perilampus. Head more elongate than 

 that of P. liyalinus, the recurved hooks, if present, very small; there 

 are two pairs of organs in a location similar to that of the hooks upon 

 the head of Perilampus, but their extremely minute size makes the 

 nature of these objects difficult to define even under the oil-immersion 

 objective. Mouth parts indefinable, considerably retracted into head. 

 Anterior margm of head much roughened. First dorsal segment 

 short, with a pair of distinct bristles situated along the apical margin, 

 the base of each within a transparent spot. Second segment broader, 

 with two apical spines farther apart than on })receding. Next seg- 

 ment much like second, but broader, with similar spines. Remaining 

 segments apparently without dorsal spines. Ventral ends of the 

 chitinous plates simple, not ending in a serrate margin or with long 

 teeth as in Perilampus. Seventh segment with a pair of spines ven- 

 trally. Last segment with a pair of stylets comparatively shorter 

 and stronger than in Perilampus. 



Dr. Wheeler's account of the effect of parasitism by Orasema upon 

 Pheidole tallies very well with our observations upon parasites 

 attacked by Perilampus, the same microcephalic characters are 

 present in the host pupae in both cases, with the peculiar transparent 

 appearance, as noted upon a previous page of this article. 



Other points in the economy of Orasema brought up by Dr. Wlieeler 

 and which at the time seemed very puzzling are apparently rather 

 easy of explanation in the light of our present knowledge of Peri- 

 lampus. It is hardly within the province of this bulletin, however, to 

 take these up in detail, and it is merely suggested here that anyone 

 desirous of doing further work upon the development of Orasema, 

 and perhaps other members of the chalcidoid family Eucharidae, 

 would perhaps do well to bear in mind the similarity of the life cycle, 

 so far as known, to that of Perilampus.^ 



RELATIONSHIP OF EUCHARIDiE AND PERILAMPID.ffi. 



The great similarity of development in the genera Orasema and 

 Perilampus can not fail to have considerable bearing upon the taxo- 

 nomic relationship of the so-called families Eucharida3 and Peri- 

 lampidae. Francis Walker, in 1846, placed the two groups together 

 under the family name Eucharidae. Ten years later, however, the 

 German hymenopterist, Arnold Forster, decided that the difl'erences 



1 During the winter of 1909-10 an extraordinary planidium was found on the hibernating larva of the 

 larch sawfly ( iVcTOa^tts crichsonii Hartig), within the cocoon. This parasite was not reared, but was Peri- 

 lampus in all probability. 



