46 



BULLETIISr 427, U. S. DEPARTMENT OF AGRICULTURE. 



and on stored potatoes conditions are such that any parasite is of 

 doubtful value. In addition, it seems to have one unfortunate habit, 

 that of becoming at times a hyperparasite on Campo- 

 plex pTithorimaeae. This habit is so unusual, however, 

 as to be unimportant. 



The record below gives the length of a life cycle : 



1915. 

 August 8. — Tuber-moth larvae parasitized by Dihrachys clisio- 



campae. 

 August 16. — Parasite larvae mature. 

 August 18. — Parasite larvae pupating. 

 August 25. — 4 parasite adults issued. 

 August 26. — 7 parasite adults issued. 

 August 27. — 1 parasite adult issued. 



Length of life cycle 13 days at an average mean temperature of 

 75° F. 



OTHER PARASITES. 



(Male and female.) 

 (Male and female.) 

 (Female.) 



Fig. 42. — Dibrachys 

 cUsiocampae: Ma- 

 ture larva. Much 

 enlarged. (Origi- 

 nal.) 



Other parasites ^ were reared from time to time in 

 small numbers from tuber-moth material collected in 

 the San Gabriel Valley. They never became at all 

 common. Efforts to rear them in the laboratory have 

 been unsuccessful thus far. Both have been seen on 

 occasion to oviposit in small leaf-mining tuber-moth larvae, but no 

 parasites have issued, and so they have not as yet been proven to be 

 parasites of the tuber moth. 



NEPEIRA BENEVOLA VAR. FUSCIFEMORA CUSHM.^ 



For some time this parasite (fig. 44) was considered 

 identical with Campoplex phthorimaeae Cushm. The 

 differences noted seemed to be variations within the 

 species. While Mr. Cole was making drawings of the 

 parasites, he noted that there were three separate types. 



Nepeira henevola var. fuscifemora Cushm. closely 

 resembles Campoplex phthorimaeae, both in appear- 

 ance and life history, but has never become as abun- 

 dant as the latter. It oviposits in half -grown leaf- 

 mining tuber-moth larvae. 



Larvae parasitized November 12 have given adult 

 parasites December 12, a length of life cycle of 30 

 days, at an average mean temperature of about 63° F. 



PERCENTAGE OF PARASITISM. 



Fig. 43.—Dibrachfs 

 cUsiocampae: Pupa, 

 lateral view. Much 

 enlarged. (Origi- 

 nal.) 



The percentage of parasitism has fluctuated so 

 greatly in the time it has been under observation that 

 it is difficult to give even approximate figures. The lowest parasitism 

 noted was 40 per cent and the highest was 95 to 100 per cent. The 



I Chittenden Nos. 2230oi« and 2230"". 



2 Chittenden No. 2230012. 



