THE CHALCIDOID GENUS PEEILAMPUS. 35 



strange little creature was discovered which was obviously the larva 

 of an insect, but which differed very materially from any familiar 

 form. It was impossible, from external characters, to assign it to 

 any particular order with assurance, and consultation with several of 

 the ablest entomologists of the country failed to throw any light upon 

 the subject. 



It was less than three-tenths of a millimeter in length, and therefore 

 almost invisible to the unaided eye, oblong-ovate in shape and dark 

 brown in color. Examination under the microscope showed it to be a 

 highly organized being with well-defined mouth parts, strong, curved 

 mandibles, conspicuous tracheal system, etc. The 13 segments were 

 well differentiated, the fii'st forming a distinct head, which was armed 

 with several recurved hooks. The dorsal segments consisted of a 

 series of heavy, chitinous, and overlapping plates, which nearly encir- 

 cled the body. Most of these were furnished with one or two pairs 

 of bristles. Ventrally the larva was furnished with several backward- 

 projecting spines, wliich were evidently ambulatorial in function. 

 An attempt to rear the adult from this larva was unsuccessful. 



Among the minor projects under way at the laboratory at tliis time 

 was a study of the biology of Dimmockia incongrua Ashmead, a rather 

 common and important native chalcidoid parasite of tachinids. As 

 a host for the rearing experiments Avith Dimmockia one of the most 

 common native dipterous parasites, Varichseta aldrichi Townsend, 

 also an important enemy of the fall webworm, was utilized. 



In the course of an examination of the pupae of this tachinid for the 

 eggs and young larvse of Dimmockia a second specimen of the remark- 

 able creatiu-e referred to above^ or to be more accurate one similar to 

 it, was encountered. This second specimen, instead of being firmly 

 attached to its host by its anterior end as was the former, was quite 

 free and crawled about over the body of the tacliinid pupa in a 

 startlingly businesslike manner. This observation very naturally 

 led to a further search through the abundant material at hand, and 

 the presence of the strange parasite, for such it was now suspected of 

 being, was found to be of not at all rare occurrence. An excellent 

 opportunity was at once afforded for ascertaining the identity of the 

 parasite and the subsequent rearings through the different stages were 

 made with a great deal of eagerness. Immediately upon the comple- 

 tion of the first ecdysis it was seen that the larva resembled rather 

 closely what was known to be the mature larva of Perilampus, and 

 the further development of the specimens under observation con- 

 firmed that suspicion. The first-stage larva is of a very unusual 

 type, wliich, with a single exception so far as known, has not been 

 observed before. This exception is the larva of Orasema viridis Ash- 

 mead, described and figured by Dr. William Morton Wheeler.^ 



1 Bulletin of the American Museum of Natural History, vol. 23, Art. 1, 1907. 



