COMPOSITION OF THE OVIPOSITOK. 



17 



of thin lamelliform pieces of similar form and structure, ansiiig 

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

 ently also homologize with the filiform, antennse-like, jointed 

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

 most Neuroptera and Orthoptera (especially in Mantis tes- 

 sellata where they (Fig. 23) closely 

 resemble antennae), which, arising as 

 they do from the arthropleural, or limb- 

 bearing region of the body, i. e. between Fig. 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 larvae 

 {Corydalis, Phryganeidce, etc.). 



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

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

 disappearance of others, and the perfection of those parts to 

 be of future use. Thus tow^ai-ds 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 withdrawn within the body, while the last, or eleventh sternite, 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.* Meanwhile 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- 

 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- 



Fig. 24. 



*In Ranatra, however, Lacazo-Duthiers has noticed the envious fact that in 

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

 l>rcgeuital (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 tesxellatn ; p, many-jointed anal stylo 

 resembling an antenna. 5-11, the last seven abdominal segments;, the S-llth ster- 

 uitcs being obsolete. — i-Yoj^i Lncnze-Duihiers. 



Fig. 24. Ideal plan of the structure of the ovipositor m the adult insect, i-'t, 

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

 eighth tergite, or anal scale; c, epimerum ; n', a, two pieces fomiing the outer pair 

 of rhabditcs; i, the second pair, or stylets; and /VUio inner pair,.or. stjug; d, Uie 



