B -3 1 h 



INTRODUCTION. 



HYMENOPTERA. 



The Order Hymenoptera comprises the Sawflies, the Gallflies, the 

 Ichneumons, the Ants, the Sand- and Wood-wasps, the Wasps 

 proper, and the Bees. 



It is now generally admitted that Hymenoptera have a right 

 to be considered the most highly developed mentally of all insects. 

 Certain forms, as the ants, the social bees, and wasps, live in large 

 communities, have a regular and organized division of classes and 

 labour, and frequently maintain complex social relations with 

 insects of other orders that, as guests or parasites, harbour in 

 their nests. 



The Hymenoptera are distinguished from all other insects by 

 the following general characters : — 



Mandibles always present and conspicuous, even when the rest 

 of the oral parts are more or less changed and abnormal. In the 

 higher forms, the thorax and abdomen are remarkably modified. 

 The first segment of the abdomen is separated from the remaining 

 segments by a complex and extremely flexible joint, and is united 

 to the posterior portion of the thorax, forming with it a consoli- 

 dated mass, which has appropriately been called the " alitrunk " by 

 Dr. Sharp. Wings four, membranous, with comparatively few 

 nervures, enclosing spaces or cells irregular in shape and limited 

 in number ; the posterior wings smaller than the anterior. 

 Abdomen in the female furnished, at its apex, with a saw, borer, 

 ovipositor, or sting. 



Larva in the more highly developed genera and famihes always 

 vermiform and footless, but in some of the lower forms with 

 thoracic and abdominal legs, the latter frequently numerous. 

 Pupa inactive, the parts as in the imago, but more or less 

 colourless and enveloped in a thin delicate membrane. 



The head of a hymenopterous insect is quite free from the 

 thorax and often remarkably mobile. It varies but little in shape : 

 the vertex (figs. 1, 2, & o, «) is usually more or less convex and 

 transverse, very often broad and subquadrate ; the clieeh (fig. 1, 6) 

 lies behind the eye, and when the lower rim of the latter does not 

 extend down to the base of the mandibles it includes the space 

 between the eyes and the mandibles; \\\q comjJound eyes {^o. l,c; 

 figs. 2 & ^, r/, c^) occupy the sides of the head, and are built up 

 generally of many facets, but in some of the ants are reduced to 

 one facet. On the vertex (sometimes a little below it) are placed 



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