GENERAL CHARACTERISTICS. 7 



externally the jointed palpi, resembling those of the maxillae, and between these 

 there is a median, sometimes bilobed, piece, called the ligula, and a pair of pieces 

 termed the paraglossae. The degree of development of the several parts varies 

 greatly in different orders, and it is often a matter of considerable difficulty to 

 determine the exact correspondence that exists between them in two insects 

 belonging to different orders. This is especially the case when the jaws have 

 been modified to form the different organs of suction that are met with. The 

 structure of these will be described in detail when the species that possess them 

 are discussed. Another organ to be mentioned in connection with the jaws is a 



MOUTH-ORGANS OF INSECTS. 



1, Head of honey-bee, from the front ; 2, Head of humble-bee, from below ; 3, Maxillae and labrum of a bee 

 (Andrena) ; 4, Maxillae and labium of saw-fly (Cimbex) ; 5, Lower view of head of carnivorous beetle 

 {Procrustes) ; 6, Maxilla of carnivorous beetle (Cicindela) ; 7, Maxilla of cock-tail beetle (Staphylinus) ; 8, 

 Maxilla of locust ; 9, Head of bug {Cicada) from the front ; 10, Head of butterfly ; 11, Head of horse-fly 

 {Tachina). 

 Labium — a, mentum ; b, ligula ; b', paraglossae ; c, palp ; d, mandible. Maxilla (e), with/cardo ; g, stipes ; 

 h, lacinia ; h', galea ; i, palp ; k, head-plate ; n, teeth on lacinia. 



membranous lobe, called the hypopharynx, or tongue, projecting into the interior 

 of the mouth from the floor of the labium. 



The thorax, or median part of the insect's body, is formed of three segments 

 called the pro- meso- and metathorax, each of which is composed of several distinct 

 pieces. The dorsal areas of the three segments are termed the pronotum, meso- 

 notum, and metanotum ; the lateral regions the pleurae ; and the inferior regions 

 the sterna. To the pleurae are articulated the three pairs of legs, each of which 

 consists primarily of five segments, named respectively, from the base to the apex, 

 coxa, trochanter, femur, tibia, and tarsus; the last, which constitutes the foot, being 

 generally tipped with two claws, and subdivided into several — often as many as 

 five — smaller segments. To the sides of the upper surface of both the meso- 



