THE INSECTS 



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branches, an outer or palp, which has the appearance of a dwarfed limb, and an 

 inner, which is in its turn double, the inner blade being called the lacinia, and the 

 outer the galea. The jaws of the third pair, constituting the so-called labium, or 

 lower lip, are constructed upon the same principle as the maxillae, but the parts 

 usually considered to correspond to the cardo are united to form a plate the men- 

 turn which is articulated by its hinder part to a sternal plate of the head, called 

 the submentum. In front of the mentum there are externally the jointed palpi, re- 

 sembling 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 

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n 



MOUTH ORGANS OF INSECTS. 



i. Head of honeybee, from the front; 2. Head of humblebee, from below; 3. Maxillae and labrum of a bee 

 (Andrena); 4. Maxillae and labium of sawfly (Cimbex}; 5. I<ower view of head of carnivorous beetle 

 (Procrustes}; 6. Maxilla of carnivorous beetle (Cicindela)\ 7. Maxilla of cock-tail beetle (Staphyhnus); 8. 

 Maxilla of locust; 9. Head of bug (Cicada) from the front; 10. Head of butterfly; 11. Head of horsefly 

 ( Tachina). 



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

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



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 espe- 

 cially 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 wiOi the jaws is a 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 



