372 INSECTS INJURIOUS TO VEGETATION. 



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 live 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 transformations. Some kinds {Hydrocampa and Petro- 

 phila) live in the water upon aquatic plants, and secure them- 

 selves in cylindrical leafy cases, fitted to cover the whole of 

 the body except the head and six fore legs, and made air-tight. 

 These cases prevent 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 pecu- 

 liar tribes of insects, which keep in check their redundant 

 vegetation, and which are fitted, by extraordinary 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 Lepidoptera with the Neuroptera^ by means 

 of the May-flies [Phryganeadoi) belonging to the latter order. 

 Those caterpillars of the Pyralides that have only fourteen 

 legs, may be called Herminians (Herminiad.e), after the prin- 

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

 gi'eat numbers 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 states, 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 rather prominent, the cross-lines 

 between them being deep. They are of a green color, with 



