THE BEETLES. 373 



of which the blood is brought in contact with the vivifying influence of the atmosphere. These 

 breathing tubes, technically called tracheae, ramify to every portion of the creature, and even 

 penetrate to the extremities of the limbs, the antennae, and even the wings, when those organs 

 exist. Their external orifices are called spiracles, and are set along the sides. 



They have very little internal skeleton, the hard materials which protect the soft vital 

 organs being placed on the exterior, and forming a beautiful coat of mail, so constructed as to 

 defend the tender portions within, and yet to permit perfectly free motion on the part of the 

 owner. Certain projections of this substance are often found in the interior, especially in the 

 thorax, a central portion of the creature, and are used for the attachment of muscles where 

 considerable power is needed. 



This external skeleton is quite unique in its chemical composition, being made almost 

 entirely of a substance called chitine, to which are added several other materials, such as 

 animal matter, albumen, and the oil which gives the bright colors so prevalent in most of the 

 species. 



There are many other interesting points in the structure of the Insects, such as the eyes, 

 the wings, the tracheae, etc., which will be described in the course of the following pages. 



The systems on which the Insects have been arranged are as perplexing as numerous, 

 differing according to the characteristics chosen by their authors. In this work the system 

 employed is that of Mr. Westwood, which seems to combine many advantages to be found in 

 the different arrangements of various authors, and is sufficiently intelligible to be understood 

 without any painful exercise of the memory. 



BEETLES; COLEOPTERA. 



THE first order, according to this author, is called the Coleoptera, a word of Greek origin, 

 signifying sheathed-winged animals, and includes all those insects which are more popularly 

 known under the title of Beetles. In these insects the front pair of wings are modified into 

 stout horny or leathery cases, under which the second pair of wings are folded when not in 

 use. The hinder pair of wings are transparent and membranous in their structure, and when 

 hot employed are arranged under the upper pair, technically called the elytra, by folds, in 

 two directions, one being longitudinal and the other transverse. On examining these wings 

 carefully, it will be seen that their supporting nervures are furnished with hinge-like joints, 

 which permit them to be folded in the right direction and no other. One of the best examples 

 of a folded wing among the Beetles is to be found in the common Cocktail Beetle (Staphylinus), 

 where the large and beautiful wings are packed away under two little square elytra, just as a 

 folded map is packed into its covers. In other instances where the elytra are very long, as in 

 the common Musk Beetle (Cerambyx), the wings are first folded longitudinally and then a 

 little piece doubled over at the tip, so as to fit within the cover. 



The mouth is furnished with jaws, often of considerable power, which move horizontally. 



The last character that must be considered in the Beetles is the mode of the metamorphosis 

 or change of form which is undergone by them before they attain their perfect state. After 

 being hatched from the egg, they take the form that is popularly known under the title of 

 grub, and is quite unlike the shape of the perfect insect. In this state they remain for various 

 periods, according to the species and the climate, and then pass into the second, or pupal 

 state, when they look much like the perfect insect, but are unable to move about. This 

 characteristic seems to separate them from the earwigs, cockroaches, and grasshoppers, which 

 would otherwise have been included in the same order with the Beetles, but are now placed in 

 separate orders on account of the character of their preliminary stages, where the shape of 

 larva, pupa, and perfect insect are very similar, and the pupa is active. 



Passing over, for the present, the details of classification, we come to the first family of 

 insects, scientifically called the Cicindelidee, and popularly known by the name of Tiger Beetles, 



