28 BUTTERFLIES. 
in the caterpillars of most swallow-tails, though in cater- 
pillars of some moths near the tail, has the office to drive off 
the numerous parasites always ready to pounce upon their 
victims. On each side of the third segment is an eye-like 
spot, nearly oval, vellow, enclosed by a ring of black, cen- 
tered with a small elongated blue dot, which is also set in 
black. In some species of swallow-tails these eye-like spots 
look very much like eyes, and are sometimes quite startling. 
Another raised yellow fold occurs on the posterior portion 
of the fourth segment; it is bordered behind with velvety 
black, but is only seen when the caterpillar is in motion. 
Other dots occur as indicated in the illustration (Fig. 28). 
Early in August, the caterpillar becomes restless and 
wanders about in search of a suitable spot in which to 
change to a chrysalis, and in which to pass the winter. 
When such a shelter has been found, it spins a little carpet 
of silk, into which it fastens the hooks of the prolegs; it then 
fastens a silken band or loop around the middle of its body 
to suspend itself. This done, it casts its larval skin and re- 
mains as achrysalis until the following spring. 
The butterfly is shown in Fig. 27, Plate IV. 
FAMILY HESPERIDA OR SKIPPERS. 
These butterflies are quite different from all the preced- 
ing ones; they differ by possessing broad heads, clothed with 
bristly hair, by having widely separated antenne, the clubs 
of which terminate by a more or less marked and recurved 
slender hooklet, and by having rather small wings in com- 
parison to the heavy bodies (Fig. 15). They are very well 
named, as they skip trom place to place amongst low herb- 
age. The caterpillars have unusually large heads, with 
strongly contracted necks; they generally make a sort of 
nest of a folded leaf or of several leaves. We havea large 
number of species in Minnesota, but none are destructive to 
fruit; most of the caterpillars feed upon the leaves of the 
various kinds of clovers, vetches and similar plants. A com- 
mon species is shown on Plate IV, Fig. 29; it is the silver- 
spotted skipper (Endamus tityrus Fab.). 
