HYMENOPTERA 223 



may assume in the female. In many Dipterous female flies 

 the hindmost segments become slender, and may either be 

 protruded considerably, or telescoped into the body, except 

 when actually employed in egg-laying. In a female blow-fly 

 there is such a telescopic tail, while in the wheat-midge or 

 bot-fly it is more or less protruded at all times. There may 

 be three or four segments thus narrowed, and the last may 

 have the dorsal and ventral plates opposable and capable 

 of grasping. Such an apparatus is called a " tubular 

 ovipositor," but it is to be remarked that it is traversed 

 by the intestine, which at once distinguishes it from the 

 second, or true ovipositor, next to be described. 



In many Orthoptera, Hemiptera, Odonata, and Hymenoptera 

 there are three segments at the end of the abdomen (the 

 8th, 9th, and loth, as commonly reckoned*), which bear 

 peculiar limb-like, and sometimes jointed projections. In 

 a cockroach the 8th segment bears an anterior pair of 

 appendages, and tlie 9th two posterior pairs. The anterior 

 pair enclose the others, and underlie them, forming the 

 lower jaw of Et forceps, whose upper jaw is formed by the two 

 posterior pairs. This forceps can be used to grasp the eggs 

 as they issue from the oviduct, and to deposit them in a 

 place of safety. What appear to be the same parts are 

 borne upon the same segments in a bee, but when 

 fully developed, they take a different form, and become 

 adapted to totally different functions. The anterior pair, 

 borne on segment eight, furnish the darts, the outer posterior 

 pair the sting-palps, and the inner posterior pair fuse 

 to form the guide. In Sirex the anterior pair form 

 the darts, the outer posterior pair the valves, the inner 

 posterior pair the guide, while the palp-like organs seen on 

 the last segment answer not to the sting-palps of the bee, 

 but to the cerci of the cockroach. In a saw-fly again, the 

 saws are the darts of the bee's sting, and the guide is still 

 to be found; the two-jointed, hairy pieces which enclose 

 the saws answer to the valves of Sirex, and: the sting.-palps 

 of the bee. Lastly, the piercing ovipositor of an Ichneumon 



, , * It is nof so easy as might be supposed to count the segments of an 

 insect's abdomen. Segments may be lost during development at the fore 

 end of the abdomen, and what appears to be a single segment may turn 

 out to be a fusion of two or even three segments. 



