8 The Structure and Special Physiology of Insects 



of the pronounced modifications and differences in their condition: these 

 are the mouth-parts and the wings. 



Insects exhibit an amazing variety in food-habit: the female mosquito likes 

 blood, the honey-bee and butterfly drink flower-nectar, the chinch-bug sucks 

 the sap from corn-leaves, the elm-leaf beetle and maple -worm bite and chew 

 I he leaves of our finest shade-trees, the carrion-beetles devour decaying 

 animal matter, the house-fly laps up sirup or rasps off and dissolves loaf- 

 sugar, the nut- and grain-weevils nibble the 

 dry starchy food of these seeds, while the 

 apple-tree borer and timber-beetles find 

 sustenance in the dry wood of the tree- 

 trunks. The biting bird-lice are content 

 with bits of hair and feathers, the clothes- 

 moths and carpet-beetles feast on our rugs 

 and woolens, while the cigarette-beetle has 

 the depraved taste of our modern youth. 



v x md 



m ' 



FIG. ii. FIG. 12. 



FIG. ii. Mouth-parts, much enlarged, of the house-fly, Musca domestica. mx.p., maxil- 

 lary palpi; lb., labrum; Ii., labium; la., labellum. 



FIG. 12. Head and mouth-parts, much enlarged, of thrips. ant., antenna; lb., labrum; 

 md., mandible; mx., maxilla; mx.p., maxillary palpus; li.p., labial palpus; m.s., 

 mouth-stylet. (After Uzel; much enlarged.) 



With all this variety of food, it is obvious that the food-taking parts must 

 show many differences; one insect needs strong biting jaws (Fig. 8), another 

 a sharp piercing beak (Figs. 9, 13, and 14), another a long flexible sucking 

 proboscis (Figs. 10 and 16), and another a broad lapping tongue (Fig. ii). 

 Just this variety of structure actual y exists, and in it the classific entomolo- 

 gist has found a basis for much of his modern classification. 



Throughout all this range of mouth structure the insect morphologists 

 and students of homology, beginning with Savigny in 1816, have be:n able 

 to trace the fundamental three pairs of oral jointed appendages, the mandi- 

 bles, maxillae, and labium. Each pair appears in widely differing condi- 

 tions; the mandibles may be large strong jaws for biting and crushing, as 

 with the locust, or trowel-like, for moulding wax, as with the honey-bee, or 



