6 



PSYCHE. 



[January — Februaiy i8 



frequently caused by them, is doubtless 

 due to the sparse distribution and the 

 isolated occurrence of many of these 

 species. 



Balbiani gives us in his latest work 

 on this subject the interesting and im- 

 portant information that he has often 

 succeeded in conveying pebrine to 

 other insects by treating their food 

 with the dejections of affected silk- 

 worms. Bombyx neustria he found 

 more susceptible than the silkworm it- 

 self, but another bombycid, Liparis 

 chrysorrhoea^ proved wholly refrac- 

 tory, seemingly because the cuticular 

 lining of the intestine is there unusually 

 thick. Dipterous maggots, larvae of 

 ants, and the meal worm (^Tenebrio 

 molitor) were also used by him in sim- 

 ilar experiments, but quite without 

 result. 



I have myself, this year, attempted 

 to convey pebrine of the silkworm to 

 various other species, obtaining my 

 material for infection from pupae a few 

 days dead, reared by myself from 

 worms conspicuously diseased. Larvae 

 of Telea polyphemus^ the fall web 

 worm {Hyphantria textor)^ the com- 

 mon cabbage worm (^Pieris rapae)^ 

 the caterpillars of the thistle butterfly 

 (^Pyrameis cardui^^ various species of 

 cutworms {iioctuidae) ^ and both adult 

 and larval Doryphora., were infected, 

 sometimes by way of the food , sometimes 

 by puncturing the skin, but in every 

 case without positive success. I ob- 

 tained, it is true, one curious result ; 

 my specimens of Melolontha^ Pieris^ 

 and Telea all developed unmistakably 



the characteristic specks and spots of 

 pebrine subsequent to infection, but the 

 most critical and protracted search of 

 their fluids and tissues failed to discover 

 the slightest evidence of parasitism, — a 

 fact which I could only explain on the 

 hypothesis that the marks on the skiw 

 were due to the direct action of the 

 material ingested or injected from the 

 silkworm, and not to any morbific sub- 

 stance elaborated within the bodies of 

 the insects experimented upon. 



You will perhaps allow me to add 

 an item upon the possible economic 

 applications of this disease. There is 

 not the slightest probability that the 

 sporozoa can be artificially cultivated 

 outside the bodies of the animals which 

 they may infest ; neither have we yet 

 any sufficient proof that forms nor- 

 mally occurring in one species will 

 multiply or permanently maintain them- 

 selves in any other. We are conse- 

 quently limited, practically, to artificial 

 measures for developing and accelerat- 

 ing this disease wherever it may be 

 found, and to more careful and ex- 

 tended experiments for its transfer 

 from the silkworm to related noxious 

 species. 



The American literature oi pebrine 

 is an absolute blank, not a single item 

 of new information concerning it hav- 

 ing been published on this side of the 

 water, nor a single observation of its 

 occurrence in this country in any other 

 form than in the common silkworm hav- 

 ing been placed on record, as far as I 

 can find. 



The notable fungous diseases of in- 



