DEFINITION OF AN INSECT. 3 



of other creatures which have really no right whatever to the 

 title. We will therefore see what an insect really is. 



Insects are technically described as being ' articulated a-m- 

 mals, breathing by trachece, divided into three distinct portion-n 

 — viz. the head., the thorax, and the abdomen — passing through, 

 a series of transformations, and having in the perfect oj 

 "•' winged " state six articulated legs and two antennaj.'' 



We will now take this description and examine it in detail. 

 The articulated animals are formed on a totally different pl;m 

 from the vertebrates, molluscs, radiata, or other divisions of 

 the animal kingdom. Their bodies are formed of a series of 

 flattened rings, within which are contained all the muscles 

 and vital apparatus. It will be seen that a vast number of 

 animals come within this definition, which includes not only 

 the insects, but the Crustacea, such as the crabs, lobsters, 

 shrimps, woodlice, and others ; the Arachnida, such as the 

 spiders, scorpions, and mites ; the Myriapoda, such as the 

 centipedes and millipedes ; and the Annelida, of which the 

 common worm is a familiar example. It is necessary, there- 

 fore, to find some mode of distinguishing tne insects from all 

 the other articulates, and, after much trouble, systematic 

 naturalists have agreed upon the short formula which has 

 already been given. 



It is there stated that insects breathe through ' tracheas.' 

 Xow tracheae are tubes composed of thin membranes, kej)t 

 open by a fine but stiff wiry thread, which is twisted spirally 

 throughout the whole course of the tube, just as a modem 

 flexible gas-tube is kept open by a spiral wire, no matt er how 

 it may be twisted or bent. This is absolutely necessary in 

 insects, for the trachese are not confined to a single portion of 

 the body, like the lungs of men or the gills of fish, but per- 

 meate the entire insect, passing through all the limbs, and even 

 reaching to the claws which terminate tne feet. Any of my 

 readers who wish to see the extraordinary manner in which the 

 breathing apparatus is disposed over the whole body should 

 look at the plates of Strauss Durckheim's wonderful work on 

 the common cockchafer, a work to praise Avhich would be 

 simply impertinent. 



I strongly advise all my readers to examine these marvellcus 

 structures for themselves. There is not the least difficulty in 



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