ENTOMOLOGY. 105 



various organs are, of course, greatly modified, some 

 being more fully developed, and others becoming 

 almost or wholly obsolete. Three principal types of 

 form in the construction of the mouth prevail among 

 haustellate insects, which have received the names 

 of Promuscis, Proboscis, and Haustellum. Each of 

 these is characteristic of a particular order, and will 

 therefore demand a detailed examination in the sub- 

 sequent exposition of the peculiar characters of these 

 orders ; at present it may be merely remarked, that 

 the tube for the transmission of the fluids is generally 

 formed by the elongation of the maxillse, accompanied 

 with some accessory parts, sometimes the upper, at 

 other times the under lip forming a lengthened sheath 

 to support and protect the other parts. 



The next primary division of an insect which re- 

 quires attention is that which may be described gene- 

 rally as lying between the head and abdomen, viz. 

 the Thorax. It is a highly important part, in as much 

 as it bears all the organs of motion, and determines 

 in some degree the whole shape of the insect ; the 

 variety of its forms and the multitude of pieces en- 

 tering into its composition, render the study of it 

 rather difficult, and this difficulty has been increased 

 by the complex nomenclature which has been assigned 

 to its parts. A slight inspection suffices, for the most 

 part, to shew that it is made up of three principal 

 parts ; the anterior of these, bearing the fore-legs, is 

 termed the prothorax ; the next, which supports the 

 middle-legs and the fore- wings, (in such species as 

 are provided with four wings,) is the mesothorax ; 



