HEMIPTERA. 349 
‘bugs. They all have sucking mouth-parts, the mandibles 
and first maxille being bristle-like, and ensheathed by the 
labium or second maxille,. Their metamor- 
phoses are incomplete, the larva being like 
the adult, except that the wings are absent. 
Many bugs secrete a disagreeable fluid from 
glands seated in the metathorax. The lice 
are low, wingless parasitic Hemiptera. The 
squash-bug (Fig. 326, Coreus tristis) and 
chinch-bug (Blissus leucopterus Uhler) are 
types of the order.* fries, squaais bus, 
While most insects live but a year or two, 
or three at the most, the seventeen-year locust (Cicada sep- 
temdecim Linn., Fig. 327) lives over sixteen years as a larva, 
< 
Fig. 827,—Seventeen-year Locust. a,b, pupa; d, incisions for eggs.—After Riley. 
finishing its transformations on the seventeenth; there is 
also, according to Riley, a thirteen-year variety of this 
species. 
The froth insect (Ptyelus lineatus) abounds on grass in 
early summer. The cochineal insect (Coccus cacti) belongs 
to the Coccide, or bark-lice; the dried female is used as 
a dyestuff, and abounds in Central America. 
* See works by Amyot et Serville, Say, Uhler, Riley, Comstock, etc. 
