50 



Two Scoliid Parasites 



the day following that of hatching the egg membrane splits dorsally 

 along its length, and the back of the larva is revealed, but the larva 

 still firmly adheres by its ventral surface to the egg membrane below, 

 thus retaining its attachment to the host. The successive moults are 

 accomplished in a similar way: the skin splits along the back and 

 gradually recedes down the sides of the larva as the latter increases in 

 circumference. The number of moults was not determined with absolute 

 certainty ; in addition to that which occurs on passing into the pupal 

 stage two were observed during the time that the larvae are attached 

 to the host, occurring in normal examples 3-4 days and 7-8 days 



after hatching. 



Days from hutching 



12 3*5 6 7 fl. 910111? 1 93 456 789 10 1112 123*56789 10 111: 



3 ,5 



.3 12 



a 9 

 <u a 





S indicates spinning 

 Growth in length of three Tiphia larvae 



The increase in length of three typical examples is shown in the 

 subjoined diagram. Until about the tenth day from hatching growth 

 is steady and regular, this being the period during which the host 

 remains alive, or at least, retains its normal shape and fcurgidity. Up 

 to the last day or two of this period it is quite active, burrowing through 

 the soil and in some cases feeding. On the last day it is without move- 

 ment, and the large anal segment has usually become translucent. 

 Until this stage is reached the parasite has retained its original attach- 

 ment, becoming considerably arched as it increases in length, and 

 hanging to one side across the back of the host like a firmly stalled 

 pillow. It now pushes out its long tapering neck, hitherto concealed. 

 and attacks the actual tissues. It usually begins behind the head, 

 eating a large hole into the thoracic segments of its now collapsed ami 



