COMPOSITION OF THE OVIPOSITOK. 



17 



of thin lamelliform pieces of similnr form and structure, arising 

 from the sternite of the ninth ring. These outgrowths appar- 

 ently also homologizc with the filiform, antennjfi-like, jointed 

 appendages of the eleventh ring, as seen in the Perlidae and 

 most Nem'optera and Orthoptera (especially in 3Iantis tes- 

 sellata where they (Fig. 23) closely 

 resemble antenme), which, arising as 

 they do from the arthi'opleural, or limb- 

 bearing region of the body, ^. e. between Fig. 2.3. 

 the sternum and episternum, are strictly homologous with the 

 abdominal legs of the MjTiapoda, the "false legs" of cater- 

 pillars, and the abdominal legs of some Neuropterous larvoe 

 {CorydaUs, Phryganeidce, etc.). 



It will thus be seen that the attenuated form of the tip is 

 produced by the decrease in size of certain parts, the actual 

 disappearance of others, and the perfection of those parts to 

 be of future use. Thus towards the extremity of the body 

 the pleurites are absorbed and disappear, the tergites overlap 

 on the sternites, and the latter diminish in size and are 

 withdrawn within the body, while the last, or eleventh sternite, 

 entirely disappears.* Meanw^hile the sting gi-ows larger and 



larger, until finally we 



have the neatly fashioned 



abdominal tip of the bee 



concealing the complex 



sting with its intricate 



system of visceral ves- 



Fig. 24. sels and glands. 



The ovipositor, or sting, of all insects, therefore, is formed 



on a common plan (Fig. 24). The solid elements of the artln'o- 



*In Itniiatrn, however, Lacaze-Dutliiers has noticed the curious fact that in 

 order to form the long respiratory tube of this insect, the tergite and sternite of the 

 pregeuitiil (eighth) segment are aborted, while the pleurites are enormously en- 

 larged and elongated, so as to carry the stigmata far out to the end of the long tube 

 thus formed. 



Fig. 23. End of the abdomen of Mantis tesxeltata ; p, many-jointed anal style 

 reseml)ling an antenna. 5-11, tlie last seven abdominal segments; thcS-Uth ster- 

 nites being obsolete. — From Lacaze-Duthiers. 



Fig. 24. Ideal plan of the structure of the ovipositor in the adult insect. l-7t, 

 the tergites, connected by dotted lines with then- corresponding sternites. b, the 

 eighth tergite, or anal scale; c, cpimerum ; «', er, two pieces forming the outer pair 

 of rhabdites; i, the second pair, or stylets; and /, the inner pair, or sting; d, the 



