55 



X, — Microscopical Observations on a Malady affecting the Common 

 House-Fly. By Cornelius Varley, Esq. 



(Read November 14, 1849.) 



The common house-fly is frequently seen dead and attached by 

 the trunk to the glass of windows, and other places, the glass 

 being rendered dim by a kind of white matter, which appears to 

 be exuded from the body of the fly. This appearance having 

 excited my curiosity, I was induced to turn my attention to the 

 subject, with a view to discover its cause, and I now take an op- 

 portunity of laying the result of my observations before the So- 

 ciety. 



This dimness appears to be the result of a peculiar disease 

 affecting the fly, which manifests itself in the proboscis, the end 

 of which becomes charged with a viscid exudation, and upon the 

 application of the trunk to the glass of windows, &c, it adheres; 

 death soon follows, and the misty appearance is produced in the 

 course of a few hours, the body of the fly being always found 

 suspended by the end of the proboscis (Plate XIII., fig. 1, a). 



In order to obtain a knowledge of the progress of this disease 

 from its earliest appearance, I cleared the windows, of one of my 

 rooms, of all flies in the state I have described, and setting my 

 children to watch, desired them to give me immediate notice of 

 any flies that might become thus attached. As soon as this oc- 

 curred, I removed them from the glass, placed them under the 

 microscope, and commenced observing attentively such changes 

 as might take place. For nearly half an hour there was no al- 

 teration ; but after that time, some of the divisions between the 

 scales of the abdomen began to appear white, as at k k, fig. 1. 

 This went on until the whole of these divisions put on the same 

 appearance. In some parts this white matter was produced in 

 such abundance as to meet that from another division across the 

 scales. In its earliest stage it appeared to be composed of my- 

 riads of round-ended cylinders, like b b, fig. 2 ; after a short time 



