344 



appendages, lying parallel to each other (fig. 20) ; the second 

 appendages similarly grow backwards ventral to these, also 

 as two hollow appendages, but more closely applied to each 

 other; the last pair, on the other hand, extend mainly for- 

 wards, and serve as a lateral protection for the other four 

 appendages which the former partly enclose. Growth is rapid, 

 and the posterior appendages assume the function more and 

 more of a protecting sheath for the other two pairs. Already 

 in the def aecating larva the second pair are closely adhering ; 

 in the larva eighteen hours later the two have almost formed 

 one tube, and by the time the larva moults, there can no 

 longer be any doubt as tO' the occurrence of a distinct cavity 

 in this structure. This cavity, however, is not formed by a 

 fusion of those of the two appendages; on the other hand, it 

 is the result of an incomplete fusion of the walls of the two 

 appendages, due to the invagination of the inner half of each 

 into its outer half. Tlie anterior pair of appendages mean- 

 while grow in thickness, and tend to fill the available space 

 enclosed by the last pair. 



The first pair of segments meanwhile give off each an 

 anterior offshoot which grows upwards and curves backwards 

 into the abdomen of the wasp (fig. 21) ; from the end of this 

 outgrowth, a second portion grows downwards and forwards. 

 This process seems to be complete at the time of pupation. 

 Already in the larva, eighteen hours after defaecation, a 

 distinct chitinous cuticle has been formed around the external 

 parts of the ovipositor, and the organ is now prepared for 

 the moult. At the time of pupation, then, the ovipositor 

 has assumed its general adult appearance, but as with all the 

 other appendages, the structures are merely moulds for the 

 adult organs. — they have attained their required sizes; they 

 have now to differentiate. 



This takes place in the early pupal period. The first 

 pair of appendages shrink, and tend to enclose the second 

 fused appendage, which has also shrunken ; the posterior pair 

 of appendages similarly shrink, and remain as somewhat 

 flattened thick sheaths, protecting the others (fig. 22). 



The aperture of the female sexual ducts is a, wide trans- 

 verse slit-like structure, and this opens into the cavity enclosed 

 by the first and second appendages. It will be referred to 

 more fully in connection with the female sexual organs. Tlie 

 second appendage becomes serrated distally and projects 

 slightly beyond the tips of the first pair. The whole struc- 

 ture, in the two-day pupa, then undergoes chitinisation, to 

 form the ovipositor of the adult. 



This complex organ consists, then, of a protecting sheath 

 (third appendage) which encloses the actual egg-depositing 



