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 
the 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- 
mothi and carpet-beetles feast on our mgs 
and woolens, while the cigarette-beetle has 
the depraved taste of our modern youth. 
Fig. ii. 
Fig. ii. —Mouth-parts, much enlarged, of the house-fly, Musca domestica. mx.p., maxil¬ 
lary palpi; lb., labrum; li., 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. 11). 
Just this variety of structure actually 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 been 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 
Fig. 12. 
