A :&RfeLlMlNARY LlSl? OF THE IJlSEOT-FAUNA OF MIDDLESEX. 29 



other gave rise to another fly exactly resembling the one reared 

 on April 4th, 1889. The circumstances connected with the 

 emergence of this fly are so entirely conclusive that it may per- 

 haps be well to relate them in detail. On examining the pupa 

 at 8 a.m., on the 14th, I observed that it had become much paler 

 in colour. At 3 p.m. I noticed the fly perched on it, with its 

 head down towards the tail of the pupa, and the extremity of the 

 abdomen of the fly still ivithin the pupa-skin. In this position it 

 remained until the following day at 5 p.m., when I transferred the 

 fly into a large glass-topped pill-box, which I placed on the table 

 in my sitting-room. On returning to the room at 7 p.m. without 

 a lamp, I was astonished to see the inside of the box brilliantly 

 lit up, the extremity of the fly's abdomen giving out a strong 

 light, about half as bright as that emitted by a full-grown larva. 

 The whole phenomena relating to the emergence of this fly from 

 the pupa, and its subsequent luminosity, were also observed by 

 my brother, who was present at the time, and can fully corrobo- 

 rate these statements if necessary. As this was a female fly I 

 decided to take her up into the big gully in the gardens, where 

 the larvae are abundant, and see if she would attract males. As 

 soon as I arrived I put the box down in the bed of the stream, 

 and the fly immediately lit up so as to again strongly illuminate 

 the inside of the box. There were lots of larvae all round, so 

 that I considered it likely there were also flies. After thirty-five 

 minutes I visited the box, but found nothing had arrived. I then 

 left her for ten minutes more, and returned with the same result. 

 During this expedition I again carefully examined many webs of 

 the larvse, and took a quantity of the mucus from them home; 

 and examined it with the microscope. I could, however, find no 

 trace of insects entangled or .their remains. I am quite at a loss 

 to explain either the light or the web, also the food of the larva. 

 I must leave these points for future investigation. 



I should mention that the flies reared on April 4th, 1889, and 

 Sept. 14th, 1890, were both females, as it is conceivable that this 

 may have an important bearing on future inquiry as to the use of 

 the light. 



A PRELIMINARY LIST OF THE INSECT-FAUNA OF 



MIDDLESEX. 



Compiled by T. D. A. Cockekell. 



(Continued from p. 8). 



Since the first part of the list was written, a good many new 

 records have come to hand, the additional sources of informa- 

 tion being as follows : — 



(9.) A. Bacot. A MS. list of 77 Lepidoptera, taken by Mr. 

 Bacot, his brother, and Mr. A. Campling, within a radius of a 



