344 INSECTS INJURIOUS TO VEGETATION. 



slender, tapering at each end, and naked, or with only a few 

 short hairs, which are rarely visible to the naked eye. Some of 

 them have sixteen legs, others have- only fourteen. The latter 

 creep very much like the span-worms, but are more active and 

 quick in their motions. Most of them hve exposed upon or 

 under the leaves of plants, and, when they come to their full 

 growth they enclose themselves in cocoons formed of folded 

 leaves thinly lined with silk, in which they undergo their trans- 

 formations. Some kinds (Hydrocamjya and Petrophila) live in 

 the water upon aquatic plants, and secure themselves in cylindri- 

 cal leafy cases, fitted to cover the whole of the body except the 

 head and six fore-legs, and made air-tight. These cases pre- 

 vent the water from getting into the lateral breathing holes of the 

 caterpillars, and contain a sufficient quantity of air for them to 

 breathe ; and, with them,, they can easily move about under the 

 surface, upon the plants which serve them for food. Some of 

 the aquatic kinds do not make these air-tight cases, for they do 

 not need them, as they breathe through fringed gills, placed 

 along the sides of their bodies. Thus we see that even aquatic 

 plants are inhabited by peculiar tribes of insects, which keep in 

 check their redundant vegetation, and which are fitted, by extra- 

 ordinary and curious contrivances, for the element wherein they 

 are appointed to live. These aquatic insects stand on the limits 

 of the order, and connect the Lepidoytera with the J^europtera, 

 by means of the May-flies {Phrygatieadcs) belonging to the latter 

 order. 



Those caterpillars of the Pyralides that have only fourteen legs, 

 may be called Herminians (Herminiad^), after the principal 

 genus in the group. The hop-vine is often infested by great num- 

 bers of these caterpillars. They eat large holes in the leaves, and 

 thereby sometimes greatly injure the plant. Caterpillars of this 

 kind have also been observed on the hop in Europe, from whence 

 ours may have been introduced ; but until specimens from Europe 

 and this country are compared together, in all their slates, it 

 will be well to consider the latter as distinct. Our hop-vine 

 caterpillars are false-loopers, bending up the back a little when 

 they creep, because the first pair of proplegs, found in other 

 caterpillars, is wanting in them. The rings of their bodies are 



