Glass 3. Insecta. Order 5. Hymenoptera. 269 



end of the female^ there is a hollow stabbing or boring apparatus, 

 through which the eggs pass when being laid, and with which, 

 in many cases, a prick or cut is made in an animal or plant, for 

 the reception of the egg ; this is the ovipositor of forms 

 described under 1 and 2 ; in others (3 to 6), the spine is not 

 simply an ovipositor, but also acts as a sting; a poison gland opens 

 into it, and the secretion runs down the canal of the spine ; with 

 this, other animals may be pierced, either in self-defence or with 

 other objects {see the Sand- wasps). The great majority of the 

 1 a r V £6 are whitish, blind grubs ; only in the Tenthredinidse and 

 Uroceridse do they depart from this type, having legs, etc. {see 

 below) . The larvae generally form cocoons for pupation. 



1. Saw-flies {Tenthredinidse). Abdomen sessile, i.e., witliout constriction, 

 broad and short ; in the females, a short, serrated ovipositor, with which small 

 cuts are made in leaves for the i-eception of the eggs. Mesothorax and metathorax 

 movahly articulated, trochanter two-jointed, fairly close veining in the wings. 

 Some of the Saw-flies reproduce parthenogenetically, either exclusively (?), or in 

 addition to reproduction by fertilised eggs. The 1 a r v se are coloured, oylindi-ical, 

 and eniciform (caterpillar-like) ; they usually possess six to eight pairs of 

 prolegs without hooks, besides the thoracic legs (c/., the Lepidoptera), and an 

 ocellus on each side of the head ; they live on trees and other plants, destroying 

 the leaves. Closely allied are the Wood- wasps, genus Sir ex, etc. (Uroceridx), in 

 which the abdomen is long, cylindrical, and provided with a longer ovipositor, 

 whilst in other respects they resemble the Tenthredinidse ; the lai-vse live in wood, 

 in which they gnaw long winding passages ; they are blind, whitish animals, with 

 thi-ee pairs of short thoracic legs, but no pi'olegs. 



2. Gall-flies (Cynipidse), small Insects in which the abdomen is short, 

 compressed, lenticular, with an ovipositor arising from the ventral surface ; wings 

 with very little veining ; two- jointed trochanter. The larvse live in galls; the 

 female bores into living portions of plants (leaves, stems, buds) by means of 

 her spine, and deposits an egg in the hole thus made ; later, the plant tissue 

 swells up in difBerent ways characteristic for each species, in consequence of the 

 presence of the larva, for it lives in, and upon, the gall thus formed. Some galls 

 are concamerated, i.e., several eggs are introduced close together into one plant, 

 and one continuous gall is formed round all the lai-vs. In many species of 

 Oynipidse, which are formd in great numbers on oak-trees, a regular alternation • 

 of parthenogenetic and true sexual generations is observed (one of each annually) ; 

 the two generations are dissimilar, and cause galls very different in appearance. 

 Other Oak Gall-flies are apparently all females. Allied to the Oynipidse is a 

 very large group, the Ichneumon-.f lies {Ichneumonidx), usually very small 

 in size, but often possessed of long ovipositors ; their larvse live as parasites in 

 '(rarely upon) insect larvse, pupse, and ova, oaterpillai-s being especially attacked ; 

 some are parasitic in other Ichneumon larvse. When the egg of an Ichneumon is 

 laid in that of another insect, the parasitic larva lives and develops at the expense 

 of the egg, and the latter degenerates. Those Ichnetunons, which are parasitic 

 in larvse, usually complete their gi-owth before the pupation of the host, they 

 then break through its skin and pupate close beside it whilst it dies ; or the 

 host pupates first, and the parasite pupates within it ; the former then dies, and 

 the latter only leaves the pupal skin of the host when it has attained the 

 imaginal state. The Ichneumon larva, which possesses very imperfect mouth- 

 parts, apparently feeds upon the blood of its host (except when parasitic in an 

 •egg) ; there may be one, or several, or many in the same individual. In some 



