206 



MR. A. M. ALTSON ON TIJE LIFE-HISTORY AND 



of 21° C, but lengthens considerably in a low temperature ; 

 although this will not delay indefinitely the emergence of the 

 adult, which either emerges upon the slightest increase in the 

 temperature, or, in the event of a steady and prolonged 

 decrease, dies within the puparium. 



The Adidt. — The adult emerges from the host puparium and its 

 cocoon by breaking away that part directl}' in contact with the 

 head (text-h'g. 8). It is furnished with a very powerful pair of 

 mandibles (text-fig. 9, a) beautifully adapted for the work in 

 hand. It breaks away the cocoon and puparium by an outward 

 movement, and does not bite the obstruction. Text-fig. 9, h 

 illustrates the outline of a section through the centre of a man- 

 dible, and shovrs its scoop-like appearance ventro-dorsally. In 



Text-figure 8. Text-figure 9. 



Text-iig. 8. — Slirivellcd and wrinkled pup;iviuin from which A. manducator has 

 emerged. Greatly raagiiitied. Original. 



Text-fig. 9. — (a) Left mandible of adult, (b) Section through centre of mandible 

 of adult. X 41. Original. 



the outward movement of the mandibles a small fracture appears 

 on the puparium, generally between the second and fourth 

 segment, gradually increasing in size until the perfect insect has 

 created an aperture large enough to enable it to escape. Obser- 

 vation has failed to disclose any use for the mandibles other 

 than breaking out of the host puparium, which operation, when 

 in progress by several insects, has been distinctly audible by 

 putting the ear over the mouth of the jar in which they were 

 confined. It is worthy of note that the mechanism of the man- 

 dibles must be diametrically opposed to that of most insects, 

 but upon consideration it seems obvious that by no other means 

 could so large a parasite escape from the puparium, which presents 

 to it a concave surface. 



