78 THE CANADIAN NATURALIST. [Feb. 



PROCEEDINGS. 



Mr. A. S. Ritchie then read a paper " On the structure of In- 

 sects." He commenced with a sketch of the history of Entomo- 

 logy from the time of Linnaeus and still earlier authors, down to the 

 present day. He then briefly reviewed the methods of classifying 

 insects which have been suggested by different authors ; some of 

 whom founded their systems on the more or less perfect changes 

 which insects undergo, others on the peculiarities of the structure 

 of the wings, or of the other organs of locomotion, some on the 

 mouth and the organs surrounding it, and so on. An account was 

 given of a few of the insects which are regarded with superstitious 

 dread by the ignorant, as the death-watch and the death's-head 

 moth. Attention was then called to the enormous numbers of 

 insects which are known to science, the number of species being 

 estimated at somewhere near 300,000 The microscropical anatomy 

 of these creatures was dwelt upon in minute detail. The tracheae 

 or air-tubes were first described : these run the whole length of the 

 body, and branch off to every part, the tubes being kept expanded 

 by an elastic spiral filament, somewhat like the spiral vessels in 

 plants. These tubes have outlets along the sides of the thorax and 

 abdomen, called spiracles, which are usually fringed with hairs to 

 prevent impurities passing into the delicate breathing-apparatus. 

 The structure of the antennae of various kinds of insects was then 

 explained. They seem to be organs of sensation, touch, and per- 

 haps of hearing. The compound-facetted character of the eye in 

 insects was next dwelt upon. These facets are often very numer- 

 ous : in the ant they are said to amount to fifty, in the house-fly 

 they number 4,000, in the dragon-fly 12,000, and, according to 

 Geoffroy, the eye of a butterfly contains upwards of 34,000 lenses. 

 The various parts of the mouth were then detailed, and after these 

 the peculiar arrangement of the legs and feet in various insects. 

 Having described the various organs of insects in the abstract, the 

 lecturer proceeded to illustrate how they varied in different kinds 

 of insects. From the beetles three species were selected— the 

 Cicindela campestris, a carnivorous ground-beetle; the Dyticus 

 marginalis, a large aquatic species ; and the Melolontha vulgaris, 

 more commonly known as the cockchafer. The sharp scythe-like 

 jaws of the tiger-beetle were described, also its large prominent 

 eyes ; its predatory habits were dwelt on at some length, also the 

 habits of the larva. The boat-like shape of the Dyticus, and its 

 oar-like feet, and various other organs, were next considered. Like 



