518 



INVERTEBRATE MORPHOLOGY. 



mxp 



Pg 



efficient organs of offence and defence, as in the Ants, Bees, 

 aiid Wasps, or else long and slender and but partially retrac- 

 tile and destitute of a poison-gland, as in the Saw-flies, Gall- 

 flies, and Ichneumonidae. 



The mouth-parts are adapted partly for biting and partly 



for licking. The mandibles (Fig. 242, 

 /////) are well developed and fitted for 

 biting in all forms, and in the Ten- 

 thrediuidae the maxillae are also like 

 those of biting insects, while the 

 inner of the two terminal plates of 

 the labium are united to form a tube, 

 the outer plates remaining separate. 

 In the Bees and Wasps the maxillae 

 (nix) become elongated and are no 

 longer adapted for biting, and the 

 inner terminal plates of the labium 

 are fused together to form a long 

 tonguelike structure, the ylossa (I), 

 the outer plates forming what are 

 termed the paraglossae (pg). The 

 entire apparatus is adapted for biting 

 and also for licking up the honey 

 contained in the nectaries of flowers. 

 The great majority of forms are 

 solitary, but a few Bees (^pis, Bom- 

 bus] and Wasps (Vespa, Sphex) and the Ants (Formica, 

 Camponotus] form social aggregations with more or less 

 pronounced polymorphism, to which reference has already 

 been made. The Gall-flies (Cynips) lay their eggs upon the 

 leaves or stems of plants, at the same time injecting a poison 

 which causes a proliferation of the plant-tissues, forming a 

 gall in the interior of which is the larva of the insect ; while 

 many forms, such as the Ichneumon-flies, Proctotrupes, Ptero- 

 malus, Microgaster, etc., are parasitic in their larval stage, the 

 eggs being deposited in or upon the bodies of the larvae of 

 other insects, a very decided check being exerted upon the 

 larvie of injurious insects, such as the Cabbage-butterfly, by 

 these forms. 



FIG. 242 MOUTH-PARTS OF 

 BEE, Anilwpliora (after 

 NEWPORT from GEGENBAUR). 



I = glossa. 

 Ip = labial palp. 

 mn = inaudible. 

 mx = maxilla. 

 mxp = maxillary palp. 

 pg = paraglossa. 



