INSECTS. 187 



live below the bark of Pine and Spruce, crawling along the tunnels bored 

 by injurious insects, and feeding on their larvae and pupa). The beetle 

 also preys on the larvae of longicorn beetles. 



Among the Hymenoptera, the digging or fossorial wasps (Sphegidce) 

 are both predatory and parasitic. They kill or deaden caterpillars, 

 beetles, plant-lice, &c., with their stings, drag them to their holes, and 

 lay eggs inside them. Wasps in general (Vespidce), and especially the 

 hornet ( Vespa crabro, itself injurious to Ash), prey on moths and flies ; 

 while ants (Formicidce), which live in large colonies within their breeding- 

 mounds, devour all sorts of injurious larvae. Among the Diptera, the 

 predatory flies (Asilidce) breed mostly in sandy localities, and attack and 

 suck many other kinds of insects ; while the leech-shaped larvae of the 

 humming- or hover-flies (Syrphidce) kill plant-lice by sucking. Among 

 the Neuroptera the scorpion - fly (Panorpa), the camel - necked flies 

 (Rhaphidia), the gold -eyed fly (Hemerobia perla], and the ant-lion 

 (Myrmdeoii) all prey on noxious insects (though the last also on useful 

 ants) ; and several dragon-flies (Libellulidce) as larvae, nymphae, and 

 especially as adults, kill many noxious insects, including moths. Among 

 the Hemiptera, scaly and other bugs (Pentastomidce, Reduviidce) prey on 

 plant-lice. But the predatory kinds in these last two orders are not so 

 numerous or useful as those in the first-named three orders. 



(2) Parasitic Insects are the chief enemies of noxious kinds ; and the 

 most important are the ichneumon-, braconid-, and chalcid-flies of the 

 Hymenoptera, and the parasitic-flies (Tachinincv) belonging to the 

 Diptera. The Jchneumonidce vary in size, but are usually long and thin. 

 The abdomen is often stalked, and the female has a long egg-layer 

 consisting of a thin borer enclosed within two lateral sheaths. The wing- 

 veins are few in number, and only form distinctly-closed cells when there 

 is a submarginal vein. The antennas are many- jointed, and usually thin, 

 seldom clubbed. The feet have usually five joints. Larvce footless, 

 smooth, generally white, soft, and tapering towards both ends. Pupa 

 soft and white, with free limbs. Adults usually fly from May till August, 

 and generally lay their eggs in the larger species of larvae of noxious 

 insects. Egg-laying sometimes also takes place in pupae, and occasionally 

 in adults ; while minute species even lay eggs within eggs of injurious 

 insects. Generation partly single, but often double, and sometimes 

 manifold ; and they increase enormously when hosts are numerous. 

 The Tachininaj, distinguishable from other flies by rough brush -like 

 hairs on the abdomen, are chiefly parasitic as larvae on the larvae 

 and pupae of moths and saw-flies. The principal species is Tachina 

 /era, which destroys large numbers of insects, and generally pupates 

 outside the host, in or on the ground, the pupa being round or oval, 

 and brown or black. 



