38 ABIA FASCIATA. 



the concave edge, looking forwards, with the ventral 

 surface ; supposing its parts to have the same relation 

 to the eggs of other insects. But when the egg is 

 escaping from the blades of the ovipositor it makes a 

 turn of 90 in the mine, by which the first-laid end 

 comes to look forwards (i. e. in the direction of the 

 head of the fly), and the concave side to look upwards 

 (i. e. in the direction of the back of the fly) ; and so the 

 position of the egg comes to be exactly the reverse of 

 what it would have been if simply extruded backwards 

 in a line with the parent. Having withdrawn the ovi- 

 positor, the fly presses together the lips of the wound 

 with the two valvular pieces between which the ovipo- 

 sitor lies when not in use, possibly having injected 

 some glutinous liquid by means of which the aperture 

 is obliterated. The mine is now a closed cavity, and, 

 as the egg grows, shows like a little blister on the leaf. 

 Generally no change whatever takes place in the paren- 

 chyma, but in a few instances Dr. Osborne observed 

 a growth of rather large globular cells, bursting off the 

 epidermis covering the egg, and indicating perhaps a 

 transition to gall growth. . . . The mine is mostly 

 beneath the upper surface, but instances are not infre- 

 quent in which it is found immediately under the lower 

 cuticle. 



In regard to the growth of the larva Dr. Osborne 

 has furnished me with the following (unpublished) 

 account, which, as being the only complete description 

 of the development of any saw-fly larva is of much in- 

 terest and value. 



The eggs are laid, if the day is sunny and warm, 

 immediately after the extrusion of the fly; that is 

 provided it is supplied with a suitable leaf. It does 

 not delay a moment for impregnation, and in the only 

 instance Dr. Osborne had an opportunity of observing 

 the behaviour of the ? towards the tf , she seemed 

 decidedly unwilling to have anything to do with him, 

 and to prefer to accomplish her business altogether 

 without his assistance. In coitu the # is bent under 



