I 



COMPOSITION OF THE OVIPOSITOR. 



17 



of thin lamelliform pieces of similar form and structure, arising 

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

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

 appendages of the eleventh ring, as seen in the Perlidse 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 (pie 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 larvae;. 

 (CorydaMs, Phryganeidw, 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 withdrawn within the body, while the last, or eleventh sternite v 

 entirely disappears.* Meanwhile the sting grows Jarger 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 arthro- 



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

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

 ]>regenital (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 tessellata; p, many-jointed anal style 

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

 nites being obsolete. From Lacaze-Duthiers. ' 



FIG. 24. Ideal plan of the structure of the ovipositor in the adult insect. l-"t, 

 the tergites, connected by dotted lines with their corresponding sternites. 6, the 

 eighth tergite, or anal scale; c, epimertim ; a, a, two pieces forming the outer pair 

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



2 



