Forest entomology . Fig. 9.—Fully developed Tortoiseshell Butterfly.(Flatters.) INTRODUCTION. 9 one, inasmuch as serial section-cutting and the highest powers ofthe microscope must be employed. This, though highly inter-esting in itself, is certainly not of vital importance to the youngstudent of forest entomology. It is, however, indispensable that thesalient features of head, thorax, and abdomen should in all cases bewell studied, and in some special instances be committed to is upon these points that generic and specific characters advanced student with a fair amount of
Forest entomology . Fig. 9.—Fully developed Tortoiseshell Butterfly.(Flatters.) INTRODUCTION. 9 one, inasmuch as serial section-cutting and the highest powers ofthe microscope must be employed. This, though highly inter-esting in itself, is certainly not of vital importance to the youngstudent of forest entomology. It is, however, indispensable that thesalient features of head, thorax, and abdomen should in all cases bewell studied, and in some special instances be committed to is upon these points that generic and specific characters advanced student with a fair amount of leisure would do well tostudy the internal anatomy of insects. The head is theoretically composed of a number of pieces, but ingeneral appearance is made up of one piece. On the under side it. lV.,f , hmd r?or!v SeeiU Fig. 10.—Typical mouth parts of insects. (Flatters.) bears the mouth, which is adapted either for biting or sucking. Themouth arrangement separates the whole of the class Insecta into twoprincipal divisions—viz., Mandilmlata, or biting insects; and Haustel-hrfa, or sucking insects. The biting mouth of the beetle and thetrunk-like proboscis of the moth are cases in point. Fig. 10 repre-sents typical mouth parts of insects. The eyes in many cases form a prominent part of the head, and areof two kinds—compound and simple. The latter are termed some insects—as, for example, in the house-fly and hive-bee—thecompound eyes cover nearly the whole of the head. The orbit of theeye is covered by a transparent skin termed the cornea. An examina-tion under the microscope shows that the surface of the cornea is 10 FOREST ENTOMOLOGY. made up of a large number of six-sided cells, each of which is termeda corneal facet (fig. 11). The ocelli or simple eyes a
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