PARASITES OF ANIMALS, 9 
insects properly called bugs, such as the squash-bug (figure 
18), strawberry-bug, bed-bug, and also the cicada or “seven- 
Fig. 12. 
° Fig. 13 
teen-year locust,” the plant-lice, bark-lice, cuckoo-spits, the 
true lice, bird-lice, ete. In this order we find, therefore, the 
greatest number of external parasites. The wings, when 
present, are often crossed upon the back, and the front wings 
are often thickened toward the base, but in other cases, as in 
the cicada and plant-lice, the wings are transparent and not 
crossed. The mouth organs form a sharp hollow proboscis, 
for piercing the bark of plants or skin of animals, in order to: 
suck up the blood or sap. When not in use tl proboscis can: 
be folded down upon the breast, by means of three joints. 
The mandibles and maxilla are four, long, slender, very- 
sharp, piercing organs, often barbed near the points. These 
are enclosed in the jointed proboscis, as in a sheath, but can 
be thrust out through the opening in the end. The proboscis. 
is formed mostly by the lower lip or labium, but the opening 
in the upper side is covered by the shorter upper lip. The 
larve of many Hemiptera resemble the adults from the first,. 
except that they lack wings; the pupa are also active and 
have the same habits. They therefore undergo less remark-. 
able transformations than those of the preceding orders.. 
Many of these insects are beneficial by destroying other in-. 
sects, but most are injurious to vegetation by sucking sap. 
Figure 12.—Apple-tree Borer (Saperda candida Fabr.), natural size. Color 
light brown with two white stripes; the lower figure represents the larve. From 
Packard’s Guide. . 
Figure 13.—Squash-bug (Coreus tristis DeGeer.), natural size. Color dark 
brown. From Packard’s Guide. 
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