232 Oti Medical Entomology . 



articulated filaments, endowed with great mobility and ex- 

 irf^uisite sensibility : they are called antennae. 



The greater part of insects are winged ; and in this case 

 thev have always six legs attached to their breast or thorax, 

 and are subject to metamorphoses. Among the aptera 

 there are some which have several hundreds of legs affixed 

 to the whole length of their bodies, and they are not subject 

 to transformation. 



Insects respire by means of vessels with elastic sides, 

 named trachea', which open outwardly by holes called 

 stigmata, placed on the sides of their bodies, and which, 

 according to Dumeril, may at the same time be the organs 

 of smell. 



They have no interior skeleton. Their skin, which per- 

 forn)S the functions of it, is generally hard, corneous, and 

 serves as a point of attachment to the muscles, which are 

 often very strong. 



Thev have no real heart, nor apparent vascular system. 

 The different parts of their bodies are moistened by a whitish 

 serous matter, the temperature of which is equal to that of 

 the medium wherein they reside. 



The presence or absence of wings, their number and tex- 

 ture, furnish simple and precise characters, by the help of 

 which the class of insects is naturally divided into seven 

 orders. 



The first order contains the insects which have four 

 wings, the lower two of which, thin and transparent, are 

 covered by the upper ones, thick and strong, which envelop 

 them like a sheath : on this account they have been called 

 ehjtrn, and the insects which bear them are distinguishud 

 by the n3in\c of coleoptcra. 



The second order comprehends insects with four wings, 

 the two upper ones of which, short and semi-coriaceous, are 

 covered by their interior edge, while the elytra of the 

 coleoplcra are merely brought together, and form a longi- 

 tudinal suture at their point of contact. These insects have 

 no jaws, and their beak is turned back on the breast. They 

 are called hemiptera. 



In the third order arc ranged insects the four wings of 

 which are coloured by scaly dust, and which have a trunk 

 of greater or less length folded back in a spiral form. 

 On account of the shiningj tints with which these insects 

 are generally ornamented, they are distinguished by the 

 name of hpidoptera. 



The insects comprehended in the fourth order have four 

 naked reticulated wings, and no sting in the anus : they 



have 



