85G PROCEEDINGS OF THE AMERICAN ACADEMY. 



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 £ inch (4.5 mm.) 

 and o's 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 difference 

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

 moulted. The rapid development in size, and consequent distention of 

 the body and the separation of the sclerites of the segments behind the 

 head, are paralleled, as Chapman says, by the greatly swollen abdomi- 

 nal region of the body in Sarcopsylla penetrans and in the female of 

 the Termitida?. In those insects this distention is due to the enlarge- 

 ment of the ovaries and of the egg« 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 hypermetatnorphosis 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 

 end 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 

 vermiform movement ; and at the same time it casts a skin, together 

 with the black head, legs, plates, etc." 



The larva, now in its second stage, passes forward and seizes hold 

 of the upper or lateral aspect of the prothoracic segment of the wasp 

 grub. On emerging it becomes shorter and thicker, "and very soon 

 loses length by that curving forward of its head which is so marked 

 in the full-grown larva, and which does not exist before its emergence." 

 The larva is now found "lying like a collar immediately under the 

 head of the wasp grub, and is attached to it by the head, though not 

 very firmly. At this stage the feeding of the young Rhipiphorus is 

 rather sucking than eating. 



