698 TEXT-BOOK OF ENTOMOLOGY 



After the wasp grub has spun the silken covering of its cell the 

 larva of Rhipiphorus may still be detected in some of them, being 

 rendered visible by its black legs and dark dorsal and ventral plates. 

 " On extracting this larva, it bears a general resemblance in size and 

 outline to the youngest larva of Rhipiphorus that I had found feeding 

 externally on the wasp grub, but with the very notable exception of 

 the already mentioned black marks. These are, in fact, a corneous 

 head, six-jointed legs, and a dorsal and ventral series of plates. I 

 immediately recognized the head and legs as identical with those of 

 the little black mite already described, but presenting a ludicrous 

 appearance in being widely separated from each other by the white 

 skin of the larva. I have no doubt that the dorsal and ventral series 

 of black marks are the corresponding plates of the mite-like larva 

 floated away from each other by the expansion of the intervening 

 membrane. By measurement also they agree exactly in size, although 

 the larva extracted from the wasp grub is ten times the length and 

 six times the width of the little Meloe-like larva. In length it is 

 1 inch (4.5 mm.), and ^ inch in breadth." 



The remarkable changes thus described in the larva of this beetle 

 after it has begun its parasitic life within the body of its host are 

 especially noteworthy because the great increase in size and differ- 

 ence in shape, as well as in habits, all take place before the insect 

 has moulted. The rapid development in size, and consequent dis- 

 tension of the body and the separation of the sclerites of the segments 

 behind the head, are paralleled, as Chapman says, by the greatly 

 swollen abdominal region of the body in SarcopsyUa penetrans and in 

 the female of the Termitidse. In those insects this distension is due 

 to the enlargement of the ovaries and of the eggs contained within 

 them, but in the Rhipiphorus it is due to the comparative inactivity 

 of the larva, and to its being gorged with an unending supply of 

 rich food, the blood and fat of its host. It follows, then, that if a 

 sedentary life and over, or at least abundant, nutrition will have 

 this effect within the short period covered by the single first larval 

 stage of the Rhipiphorus, it is reasonable to infer that the hyper- 

 metamorphosis is also due to the same factors. 



Chapman then goes on to say that finally, within six hours of the 

 time of spinning up of the wasp grub, the Rhipiphorus larva at the 

 cud of Stage I., which is " usually in motion, and for its situation 

 might be called tolerably active, is seen to lay hold of the interior of 

 the skin with its anterior legs, and keeps biting and scratching with 

 its strong and sharp jaws until it is able to thrust through its head, 

 when, in less than a quarter of an hour, it completely emerges by a 



