THE OVIPOSITOR 



167 



As to the homology and continuity of these cercopods with the 

 ventral outgrowths of the embryo, several embryologists, notably 

 Wheeler, are emphatic in regarding them as such. It thus appears 

 that either the embryonic appendages of the seventh or eighth, 

 ninth or tenth uromere may persist, and form the cercopoda of the 

 adult. 



The ovipositor. The end of the oviduct is guarded by three pairs 

 of dhitinous, unjointed styles closely fitted together, forming a 

 strong, powerful apparatus for boring into the ground or into leaves, 

 stems of plants, the bodies of insects, or even into solid wood, so 

 that the eggs may be deposited in a place of safety. In the ants, 

 wasps, and bees the ovipositor also functions as a sting, which is 

 further provided with a poison-sac. 



Morphologically, the ovipositor is composed of three pairs of un- 

 jointed styles (rhabdites of Lacaze-Duthiers, gonapopliyses of Huxley), 

 which are closely oppressed to or sheathed within each other, the 

 eggs passing out from the end of the oviduct, which lies, as Dewitz 

 states, between the two styles of the lowest or innermost pair, and 

 under the cross-bars or at the base of the stylets mentioned; the 

 styles or blades spreading apart to allow of the passage of the egg. 



The ovipositor is best developed in the Thysanura (Fig. 179, Cam- 

 podea excepted), in Orthoptera (Fig. 184), in the Odonata, Hemiptera, 

 certain P h y s a p o d a, 

 Rhaphiidse, and in the 

 phytophagous Hymen- 

 optera, where it is curi- 

 ously modified to form 

 a rather complicated 

 saw for cutting slits in 

 wood or leaves (Fig. 

 185). It is wanting or 

 quite imperfect in 

 Coleoptera, Diptera, 

 and Lepidoptera. 



Morphologically, the ovipositor appears to be formed out of the 

 abdominal appendages of the seventh, eighth, and ninth segments of 

 the female, which, instead of disappearing in the orders first men- 

 tioned, persist as permanent styles. 



Wheeler asserts from his study of the embryonic development of 

 Xiphidium " there can be no doubt concerning the direct continuity 

 of the embryonic appendages with the gonapophyses." He goes on 

 to say : 



FIG. 185. Saw of Ilylotoma : <i, lateral scale; i, saw;/, 

 g-orget ; ~(t. 7th tergite ; 6s, 6th sternite ; oi\ oviduct; in, intes- 

 tine. After Lacaze-Duthiers. 



