214 HIGH SCHOOL ZOOLOGY. 



means of which they run over the surface of water (Gerris) ; 

 others have a flat, depressed body, with short legs, like the 

 bed-bug {^Acanth'm lectularia), while among the phytophagous 

 forms, to which some destructive species like the chinch-bug 

 [Rhyimrochromus leucopterus)^ and the squash-bug {Coreus 

 tristis) belong, a gi-eat variety of form exists. 



31. All the Insecta mentioned above are spoken of as ame- 

 tabolic forms (^Ametabola), on account of the fact that they do 

 not undergo a metamoi-phosis. Those on the other hand now 

 to be dealt with are metabolic (Metabola). 



At first sight the Neuroptera, on account of the wings, seem 

 to be closely allied to the May-flies referred to above, but their 

 larvse pass through a resting (pupa) stage, during which they 

 attain their aduit form. The terrestrial lai-vse of Myrmeleon 

 are called ant-lions, as they feed on ants, which they catch by 

 preparing sand-pits for them to roll into. They spin a cocoon, 

 in which they pass their pupa-stage. The aquatic laiwsa of the 

 caddis-flies (Phryganeci) live in cases, formed of sand or bits of 

 twigs, in which they afterwards pass the jjupa-stage. This 

 group (Triclioiiterci) is an interesting one, because it leads to 

 the Diptera and Lepidoptera, both on account of the fact that 

 the anterior wings are hairy, and because the mouth-parts ap- 

 proach the structure met with in these orders. The latter is 

 true also of the genus Panorpa, which is further remarkable for 

 having caterpillar-like larvae. 



32. From the carnivorous terrestrial lanrse of the Neuroptera 

 we pass naturally to the carnivorous forms of beetles — Coelop- 

 tera, — which are marked by a more complete conversion of the 

 anterior wmgs into elytra than we have yet met with, and by 

 a greater resemblance of the mouth-parts to those of the Orthop- 

 tera, than exists in other insects. More than a third of the known 

 species of insects belong to this order j it may be gathered, there- 

 fore, that within comparatively narrow limits of structural 

 modification there is a sui-prising wealth of form, a.ssociated 



