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 v/ith my own eyes what 

 the Italian naturalist had reported in so erudite and 

 pleasing a manner. I did not then imagine that it 

 M'ould 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. Vsdlisnieri, it was not difficult for me to 

 investigate some of the circumstances better, and to 

 consider them under a different point of vie\v. It is 

 not indeed very wonderful to discover something 

 new in an object, though it has been aheady care- 

 fully inspected with very good eyes, w^ien 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 Reaumur, 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 {Cijnips) 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. 



