acquire wings occasionally ; while in some species, two forms are habitually 

 met with, in one of which the wings are more or less rudimentary, while in 

 the other they are fully developed. 



Hitherto we have been discussing land-bugs, but several families of the 

 Heteroptera are aquatic, and among them we iind the largest 

 species of the sub-order. Water-Bugs. 



The first family includes the Hijdrometridxe , the water- 

 measurers, which are long, narrow, black insects, often with fine silvery 

 pubescence. They have very long middle and hind-legs, and the front-legs are 

 directed forward. Here, too, we meet with both winged and apterous adult 

 individuals of the same species. They measure from one to three-quarters of 

 an inch in length, and are found running rapidly on the surface of the water, 

 and feeding on small insects. They can also dive when alarmed. One genus 

 of this family, Halobates (Esch.), is found running on the surface of the open 

 ocean in various regions of the tropics. 



The Nepidce, or water-scorpions, have an oval and rather flattened body, 

 terminating in a breathing tube of nearly half its length, and the front pair 

 of legs have thickened femora, and project forwards in such 

 a manner as to suggest the pincers of a scorpion. Our British Water-Scorpion, 

 species, Nepa ciiierea (Linn.) is a brown insect, nearly an inch 

 long exclusive of the spiracular tube, and is found in muddy, stagnant pools. 



Eanatra linearis (Linn.) is an insect allied to the last, and belonging to the 

 family Banatridce. It is, however, very long and narrow, and of a lighter 

 yellowish-brown colour. The middle and hind-legs are very long and slender, 

 and the front pair are much longer and less thickened than in Nepa. It 

 measures nearly three inches in length, of which the abdominal breathing- 

 tube occupies nearly half. It is not a very common insect in England, and 

 creeps about at the bottom of stagnant water. 



The largest Heteroptera belong to the family Bdostomatidce, which is not 

 British, though common in most of the warmer parts of the world. They are 

 oval insects, with the legs flattened, especially the front femora. The insects 

 sometimes measure four and a half inches in length, and six inches or more 

 in expanse of wing. They are of a yellowish-brown colour. In the evening 

 they leave the water, and fly about. This is a common habit with many 

 water-insects, which enables them to migrate from one place to another, if 

 the ponds in which they live dry up. In America, where one or two 

 species are common, they are sometimes attracted in large numbers by the 

 electric light. They feed on small fish, frogs, etc., as well as on water-insects. 



The water- boatmen (Notonectida') are represented in England by one or two 

 yellowish species, about half an inch long, with flattened hind-legs fringed 

 with hairs, and which stand out from the body in the position 

 of oars. They are used in a similar manner, for the insects Water-Boatmen, 

 float on their backs, and row themselves about with them. 

 Zaitlw, aurantiaca (Leidy) is a light brown North American species. 



Among the remaining water-bugs are the Gorixidce, which are not unlike the 

 NotonectidcE, but are smaller, much broader in proportion, especially the 

 head, and more obtuse behind. They are brown or black, glossy, with 

 yellowish stria? above. 



A friend once showed me an absurd error with respect to the term water- 

 boatmen, which is frequently applied to different species of water-bugs. 

 It occurred in connection with the habits of some South American birds, 

 in an ornithological work, the name of which I have forgotten, and ran 



