HYMENOPTERA. 593 



In connection with the great power of flight, the longitudinal 

 trached. trunks give rise to vesicular dilatations, of which two at 

 the base of the abdomen are conspicuous by their size. 



The female sexual organs usually possess very numerous (up to 

 one hundred) many- chambered egg tubes, and a large receptaculum 

 seminis with accessory glands. A special bursa copulatrix is absent 

 (fig. 488). When a sting is developed, filiform or branched poison 

 glands with a common reservoir and a duct opening into the sheath 

 of the sting, are present. In the male sex the ducts of the two 

 testes are connected with two accessory glands, while the common 

 ductus ejaculatorius ends with a large protrusible penis. 



With the exception of the leaf -wasps (Tenthredinidce), and wood- 

 wasps ( Uroceridce), the larvae are apodal and live either parasitically 

 in the body of insects (the Pteromalince pass through various larval 

 stages, undergo- 

 ing a kind of 

 hypermetamor- 

 phosis) or in 

 plants, or in 

 brood spaces 

 (cells) formed of 

 animal and vege- 

 table substances. 

 The former, like 

 the cater illars 



FIG. 488. The viscera in the abdomen of the queen bee (after 



of the butterflies, R. Leuckart). D, alimentary canal ; .R, rectum with rectal glands 

 V>Acirlac and anus 5 Gfc > chain of Ranglia; Or, ovary; So, receptaculum 

 . ' seminis ; Gl, reservoir of poison gland ; St, sting. 



the six thoracic 



legs, six to eight pairs of abdominal legs, and live free on leaves ; 

 the latter are grub-like, find the nutritive material in their cells, 

 and are in part fed during their growth. Almost all e.g., the 

 larvae of bees and wasps possess a small retractile head with short 

 mandibles and pointed pieces (maxillae and labium). The anus is not 

 developed, for the stomach is blind and does not communicate with 

 the hindgut, which receives the Malpighian tubules. Most of the 

 larvae, when they enter the pupal stage, spin an irregular invest- 

 ment or a firmer cocoon of silk-like fibres. The larvae of bees 

 and wasps then soon undergo a moult (when they get rid of 

 their excrementitious matters), and enter upon a stage which 

 precedes that of the pupa and is called by v. Siebold the pseudo- 

 pupa (fig. 489). 



38 



