26o THE BRITISH NATURALIST. [November 



Dorcus, Broscus, Emus, Creophilus, Ocypus, Staphylinus, Philonthus, 

 Quedius, and Oxyporus may be distinguished from the females by the 

 jaws or mandibles being \ r ery much larger and more powerful. 



X. — Disparity in Abdomens. 



Whilst the sex of every insect can be determined by an examination 

 of the abomen, still the difference is not always apparent to the naked 

 eye. However, in the Lepidoptera it is easily discerned in Liparis, 

 Dasychira, Gastropacha, and Nonagria by the large size of the female's 

 abdomen, that of Liparis monacha being furnished with a most 

 visible ovapositor. The female of Macrogaster arundinis has an un- 

 usually long abdomen, and those of Chilo and Orthotaelia have them 

 longer than the males. A greater difference may be seen in the sexes 

 of Eriogaster lanestris, the male having a bushy tuft of hair at the tip ; 

 whilst the female has an abdomen of large size, the end being as it 

 were swelled into a large grey ball. Many males of the Lepidoptera 

 possess an anal tuft of hair, and may be distinguished by it, but in 

 Sesia it is possessed by both sexes, although of different shape. 



Stinj. — All the females of the Fossorial Hymenoptera are armed 

 with stings, exept those of Formica, Tapinoma, Andrena, Ciliosa, 

 Dasypoda, and Macropis. The females of Chrysis, Hedycheum, and 

 Ichneumon also have stings, but to a less degree. 



These must not be confounded with the sting inflicted by the 

 Hemipterous genus, Notonecta — which is done by means of its 

 rostrum ; nor with the stings of the. Cuficidae and Tabanidae, which are 

 caused by the skin being pierced by the proboscis and blood sucked. 



Stout anal spike. — Two families of the Osthoptera — Acriolidae uand 

 Locustidae — are distinguished from each other by the females of the 

 former possessing a long sword-like spike. In the Achetidae, the 

 females of Acheta and Nemoria also possess it, but not of Gryllotalpa. 

 In the Hymenoptera the females of Sirex, Xiphydria, Xyela are 

 possessed of tolerably long spikes or borers ; and those of Cephus, Janus, 

 Clepter, and some of the Chalcididae and Cynipidae, of short ones. 



In the Diptera the females of the Tipulidae, Cecidomyidae, and 

 Xylophagidae are possessed of short anal spikes or borers. 



In Coleoptera the females of Lymexylon, Hyleccetus, Astynomus, 

 and a few others, are possessed of short borers ; but in Mordellae both 

 sexes have anal spikes. 



Flexible anal spikes. — The females of Fcenus, Rhyssa, Pimpla, 

 Cryptus, Bracon, Spathius, Agathis, Micrcelus, and Callimone are 

 possessed of long flexible anal spikes or borers. . All these spikes are 

 composed of three pieces which fold together into one. 



In Neuroptera the females of Raphidia are furnished with anal spikes. 



Saws. — The females of the Tenthredinae have a saw at the extremity 

 of the abdomen. 



