348 ZOOLOGY 
a silk gland. The larvae of another genus, Mantispa, are para- 
sitic ; they pass their life in the ovisacs of spiders, into which 
they burrow to devour the ova. 
Family 6. PHRYGANIDAE.—This family is sometimes placed 
in a distinct sub-order, the Trichoptera; it comprises the 
insects popularly known as caddis-flies. The head bears 
long filiform antennae, and a pair of hemispherical projecting 
eyes. The prothorax is small; the wings have few veins, and 
are longer than the body; the posterior pair can be folded. 
The wings are covered, as in the Lepidoptera, with microscopic 
hairs or scales. The mouth parts are rudimentary, more 
especially the mandibles, and the first maxillae and labium are 
modified. The resemblance of this family to the Lepidoptera 
is further marked by the general appearance of the imago, 
which approximates to that of some members of the Micro- 
lepidoptera, and of the cylindrical larva and quiescent pupa ; 
the latter resembles that of a moth, but has free limbs and 
wings. 
The larvae known as caddis-worms live in tubular cases, 
which they build up of particles of sand, shells, or bits of 
erass or other plants, the material varying in different species. 
At times they are wholly retracted within these cases; at 
other times their head and thorax project, and they walk 
about carrying the case retained round their abdomen by two 
recurved hooks. Like the EPHEMERIDAE and LIBELLULIDAE, 
some of the larvae have their tracheal system closed, and 
carry tracheal gills. They are either carnivorous, and then 
very voracious, or purely herbivorous. The case is closed at 
both ends at the end of larval life, and serves as a cocoon for 
the pupa, which developes into the imago out of the water. 
The female deposits her eggs in gelatinous clumps on sticks 
or stones in the water. 
Orper 4. LEPIDOPTERA. 
CHARACTERISTICS.—Lnsects with suctorial mouth parts, which take 
the form of a spirally rolled proboscis. The four wings are 
similar, and are covered with minute scales. The prothorax 
is fused with the mesothorax. The metamorphosis is complete. 
