Mr. H.H. Corbett, M.R.C.S. read a paper on “The First Principles of Entomology.” In giving a short historical sketch of the science, the lecturer alluded to the interest taken in it by Aristotle, Pliny. Virgil, and stated that little further was done until the time of Linnaeus, in the 17th century. The system of classification adopted by this great naturalist has undergone considerable alteration. Several of his orders of insects included what are now placed amongst animals, such as spiders, scorpions, woodlice, centipedes, crabs, etc.
The lecturer then gave a definition of an insect and a careful general description of its anatomy, noting the number of rings or segments of which the body is composed, and enumerating the appendages of each portion. One forms the head, three the thorax, to which are attached the legs and wings when they are present, and the remaining nine form the abdomen.
The internal anatomy of an insect consists of a blood circulatory system, a respiratory system – the air passing through apertures (spiracles) at the sides of the abdomen into tubes (trachea), which ramify through the whole of the body; a digestive system, consisting of alimentary canal, liver, etc.; a nervous system, made up of a double chain of ganglia and fibres, comparable to the sympathetic system in vertebrates. It is doubtful whether insects feel pain. And, indeed, it may be said that a wasp, divided by a pair of scissors is, perhaps, happier than any whole wasp, because it can eat for ever and never get full.
An insect may be briefly described as an animal with its body divided into three portions, head, thorax, and abdomen, and having six legs and generally two or four wings. Insects like all other animals begin life as eggs, which when hatched become larvæ or grubs. The larvæ become pupae and the pupæ develop into the perfect insect or imago. The three stages may be very similar one to another, the change being a very gradual one, or they may differ widely, and the change be sudden. In the former case the metamorphosis is said to be incomplete, in the latter complete.
The essential difference between the three consists in the power of reproduction being limited to the perfect insect. Probably the earliest form of insect was an aquatic species, allied to the crustaceaus and the myriapods, the nearest approach to such a type being found in Lepisma (sugarlouse) or in some of the orthoptera. A classification of insects upon a supposed archaic system, is impracticable, and failing this the alternative is taken of classification by type. In explanation of the meaning of the latter a group of moths was exhibited, showing the connections one with another. A type of the Group Noctuinæ being placed in the centre and radiating from it other groups. The lecturer then gave a short description of a type of each of the principal order of insects and also alluded to the alternation of generations in aphids.