COMPOSITION OF THE OVIPOSITOK. 



17 



of thin lamelliform pieces of similar form and structure, arising 

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

 ently also honaologize with the filiform, antennae-like, jointed 

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

 most Neuroptera and Orthoptera (especially in Mantis tes- 



sellata where they (Fig. 23) closely c^? e * 



resemble antennae), which, arising as ^Ggga^gftv^ "A _ 



they do from the arthropleural, or limb- [^ _( ^ J~ 



bearing region of the body, i. e, between rig. 23. 



the sternum and episternum, are strictly homologous with the 

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

 pillars, and the abdominal legs of some Neuropterous larva? 

 (CorydaMs, 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 OA T erlap 

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

 withdrawn within the body, while the last, or eleventh sternite, 

 entirely disappears.* Meanwhile the sting grows 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- 

 sels and glands. 

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

 on a common plan (Fig. 24). The solid elements of the arthro- 



*In Ranatra, however, Lacaze-Duthiers has noticed the curious fact that in 

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

 pregenital (eighth) segment are aborted, Avhile the pleiirites 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 tesseUatn ; p, many-jointed anal style 

 resembling an antenna. 5-11, the last seven abdominal segments; the 8-1 1th ster- 

 nites being obsolete. From Lacaze-Duthiers. 



FIG. 24. Ideal plan of the structure of the ovipositor in the adult insect. 'i-"t, 

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

 eighth tergite, or anal scale; c, epimerum; ', , two pieces forming the outer pair 

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



31- 



