162 
INSECTS. 
and running with agility. It then climbs up the stem of a plant to undergo 
its transformation. In some of the smaller species the pupa does not leave the 
water, but rises to the surface, and the fly emerges from the floating pupal skin. 
Caddis-flies are divided into seven families, arranged in two groups chiefly 
distinguished by the number of joints in the maxillary palpi of the male insect. 
In the first section—Inaequipalpia—the maxillary palpi of the male are composed 
of two, three, or four joints, never five; thus differing from those of the female, in 
which the number of joints is always five. This section contains four families— 
the Phryganeidce, Limnophilidce, Sericostomatidce, and Hydroptilidce ; the life- 
LIFE-HISTORY OP THE CADDIS-FLY. 
1, Larva ; 2, Pupa ; 3, Larva in its case ; 4, Perfect insect. 
history of a species of the typical genus ( Limnophilus) being depicted in our illus¬ 
tration. The second section—zEquipalpa—is characterised by the fact that the 
maxillary palpi of the male are five-jointecl like those of the female; it includes 
the families Leptoceridce , Hydropsychidce, and Rhyacophilidce. 
Flat-Winged Group,— Suborder Planipennia. 
The members of this group are distinguished from the last by having both 
pairs of wings formed nearly alike, and usually provided with a closely reticulated 
system of nervures, with numerous transverse branches. The wings—which are 
incapable of being folded up—are for the most part naked; and, when at rest, are 
turned back in a slanting position against the sides of the body. The mouth-organs 
are well-developed, the mandibles in some cases attaining extraordinary proportions. 
The first family is that of the scorpion-flies ( Panorpidce ), which have a slender 
body, and the head turned downwards and prolonged in the form of a beak, 
resulting from the elongation of the clypeus in front, and of the lower lip 
and maxillae behind. The mandibles are rather short and narrow ; the maxillae, 
which are fused with the mentum, have five-jointed palpi; and the narrow lower 
lip is bifid at the extremity, with three-jointed palpi. The antennae are setiform, 
and inserted between the rather prominent eyes, and below the ocelli, which are 
usually distinct. The prothorax is short and collar-like; and the wings of these 
