60 



Notes on Certain ''Pores" on the Veins of 



SOME DiPTERA. 



By Feazer S. Crawford. 



[Read Sept. lo, 1889.] 



Plate IY. 



There has lately been a controversy between two eminent 

 dipterists, Dr. Williston, of the United States, and Mr. F. A. A. 

 Skuse, of Sydney, whether the parasites of Icerya Purchasi and 

 Monojylthhus Crmvfordi are identical ; the affirmative view being 

 originally promulgated by myself. 



Dr. Williston had to base his opinion on specimens more or 

 less mutilated, and without any certain knowledge of the host 

 from Avhich each was bred, whereas Mr. Skuse was enabled to 

 breed the insects, and therefore to examine them to the best 

 advantage. 



Having lately had an opportunity of thoroughly re-examining 

 the venation of the wings of these insects, I discovered that my 

 original determination was incorrect ; and I take this opportunity 

 of corroborating Mr. Skuse's opinion that the insects are specifi- 

 cally distinct. 



In the course of this investigation I discovered on certain 

 veins peculiar processes, which I call " pores." These are very 

 small bodies, circular in shape, hardly raised above the level of 

 the vein, and apparently having an opening in the centre, but of 

 this fact I do not feel at all sure. They are generally on the 

 upper surface of the wing, are slightly darker in colour than the 

 vein, and so small as to require a half inch objective to detect 

 them. So far as my observations extend, they number from 

 five to eight when present, and their number and position are 

 constant in each species, and occasionally they are accompanied 

 Avith a slight dilation of the vein at the spot where they appear 

 (plate iv., fig. 2«). 



Now on the last section of the third longitudinal vein of 

 Lestophon^is leery ct", Will., there are three of these pores (plate 

 iv., fig. 1), but on the same part of L. monophlebi, Skuse, there 

 are but two (figs. 2 and 2a). From the knowledge gained by 

 examining other diptera, I feel confident that this apparently 

 trifiing dift'erence is in reality a specific distinction of great 

 importance. 



Mr. Skuse has obligingly informed me that these "pores" are, 

 he believes, homologous with what Jurine (Nouvelle methode du 



