251 lAi"-ii. 



SIMULIUM FEEDING UPOX CHRYSALIDS. 

 BY DR. H. A. HAGEX. 



In Colville Valley, Washington Territory, July 24t]i, I had the 

 chance to observe the destruction of the pine trees (P. ponderosa) by 

 the caterpillar of a butterfly (Pieris menapia). The details will be 

 published in the Proc. Boston Nat. Hist. Soc. Small flies were very 

 numerous around the chrysalids and caterpillars ready for pupation. 

 These flies were so eager and so little shy, that they could be almost 

 taken with the hands. Tbey proved to be the "black fly" {Simidium). 

 There is scarcely any doubt, that they live on the defenceless chrysalis, 

 probably sucking the tail, as I found among the alcoholic specimens 

 some flies still hidden in the dense tail-silk. The fi*esh chrysalis is 

 rather lively. One on a young shoot of pine made the most convul- 

 sive motions, when only a leaf was touched. The end of the tail 

 would be just the spot most difficult to defend against disturbance 

 from an enemy. Perhaps, the curious fact that the numberless chry- 

 salids in the crevices of the pine trees were all hanging down, instead 

 of being erect and kept in this position by a thread around the body, 

 may be the consequence of the constant attacks by these flies. The 

 threads may have been finally broken by constant convulsions. The 

 circumstance that a large number of the chrysalids were dry and dead 

 without containing parasites, speaks in favour of the supposition, that 

 they have been emptied by the constant sucking of Simulium. It is 

 generally accepted, that Simulium lives only on warm-blooded animals. 

 But it is obvious that these millions of little flies would, in this case, 

 have no chance of food. Large animals shun as much as possible such 

 places where Simulium swarms in the day time, and smaller animals 

 are certainly not so common as to be sufiicient for their food. If it is 

 accepted that Simulium can live on insect-blood — and there is, indeed, 

 no reason to doubt it — at once their existence is easily understood. 

 May this not be the same w'ith mosquito females ? The species of 

 Simuhum seems to be identical with the common Xew England " black 

 fly," but as this species is still undescribed, a detailed comparison has 

 to be made to decide about the identity. It was, indeed, wonderful, 

 that our whole party of five men and eight horses were not molested 

 at all by the flies on those places, though they were more than annoy- 

 ing in other places where the butterfly was wanting. The seemingly 

 strange assumption that Simulium may feed on caterpillars and chry- 

 salids is corroborated by the discovery that Pulex irritans feeds upon 

 caterpillars (Entom. xv, p. 70). The stomach fluids of the fleas were 



