402 INSECT ARCHITECTURE. 



covered with yellow hair. This fly appears to have 

 been first discovered by Vallisnieri, who has given a 

 curious and interesting history of his observations 

 upon its economy. " After having read this account," 

 says Reaumur, " with sincere pleasure, I became ex- 

 ceedingly desirous of seeing with my own eyes what 

 the Italian naturalist had reported in so erudite and 

 pleasing a manner. I did not then imagine that it 

 would ever be my lot to speak upon a subject which 

 had been treated with so much care and elegance ; 

 but since I have enjoyed more favourable opportuni- 

 ties than M. Vallisnieri, it was not difficult for me to 

 investigate some of the circumstances better, and to 

 consider them under a different point of view. It is 

 not indeed very wonderful to discover something 

 new in an object, though it has been already carefully 

 inspected with very good eyes, when we sit down to 

 examine it more narrowly, and in a more favourable 

 position ; while it sometimes happens, also, that most 

 indifferent observers have detected what had been 

 previously unnoticed by the most skilful interpreters 

 of nature."* 



From the observations made by RtSaumur, he 

 concluded that the mother-fly, above described, de- 

 posits her eggs in the flesh of the larger animals, for 

 which purpose she is furnished with an ovipositor of 

 singular mechanism. We have seen that the ovi- 

 positors of the gall-flies (Cynips) are rolled up within 

 the body of the insect somewhat like the spring of a 

 watch, so that they can be thrust out to more than 

 double their apparent length. To effect the same 

 purpose, the ovipositor of the ox-fly lengthens, by 

 a series of sliding tubes, precisely like an opera- 

 glass. There are four of these tubes, as may be 

 seen by pressing the belly of the fly till they come 



* Reaumur, Mem. iv. 505. 



