348 ZOOLOGY 



a silk gland. The larvae of another genus, Mantissa, are para- 

 sitic ; they pass their life in the ovisacs of spiders, into -which 

 they burrow to devour the ova. 



Family 6. Phryganidab. — 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 

 grass 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 Ephemeeidae 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. 



Oedee4. lepidoptera. 



Chaeactekistics. — Insects 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 ftised with the mesothorax. The metamorphosis is complete. 



