INSECT STRUCTURES 



Their purpose is primarily for feeling, but many forms 

 have organs of smell located in the antennae. Male mos- 

 quitoes hear with the antennae and the sense of taste, 

 being closely related to smell, may be found in some, 

 although this is by no means certain. 



The eyes of insects are of two kinds, simple and com- 

 pound. Some forms have both, some only the one or the 

 other and some have neither, being entirely blind. The 

 compound eyes are borne by all the common insects. 

 They consist of a great number of separate lens-like struc- 

 tures crowded together to make one eye. Each one of 

 these has its own field of vision, the object as seen by the 

 insect consisting of a great number of separate parts 

 thrown on its retina and forming a mosaic showing the 

 shape of the object. There may be from a very few, fif- 

 teen, to as many as fifty thou- 

 sand separate lenses or facets 

 to the compound eye. In many 

 insects the eyes take up the 

 greater part of the head. The 

 simple eyes, more frequently 

 called ocelli, vary in number 

 from one to several. They are 

 small and their uses are not 

 certainly known. 



On the lower or anterior 

 edge of the epicranium are 

 attached the mouth-parts. 

 These are, in the typical in- 

 sect, an upper lip or labrum, 

 a lower lip or Idbium, a pair of jaws or mandibles, one 

 on each side just below the labrum, and just below 

 these, a pair of supplementary jaws or maxillce. On each 



FIG. 2. Mouth-parts of Chew- 

 ing Insect (Grasshopper). 



a, labrum; l.clypeus; 2, labrum, 



? roper ; b, mandibles; c, labiuni; 

 , submentum; 2, mentum; 3, ligula; 

 4, palpiger; 5, palpus; d, maxillae; 

 1, cardo; 2, stipes; 3, palpifer; 4, 

 palpus; 5, lacinia; 6, galea; e, hypo- 

 pharynx. 



