INSECTS 25 



SOME WATER INSECTS. 



CHARLES C. ADAMS. 



IN field and forest bright-colored and face of the water. Surface insects, such 



active insects attract our attention, as the Water-Skaters, found on quiet 



Aquatic insects, on the other hand, do not, ponds and streams, and their marine rela- 



as a rule, possess such bright colors as tives, Holobates, accomplish this by 



their land relatives nor move about with means of fine hairs which cover the feet 



as great rapidity, yet it does not follow where they touch the water. The same 



that they are less interesting. physical principal is involved here, as 



As would be expected, some of the when a needle or wire is floated upon 



most interesting things about these ani- water, that of surface tension, 



mals are connected with modifications of The fine hairs on the body of a water 



their form which have resulted from their insect act in the same way as those on the 



aquatic life. It is believed that the ances- feet, and thus keep the insect dry when 



tors of water insects have been land in- below the surface. These insects are thus 



sects which invaded the water and have able to breathe as land insects, on account 



thus become greatly modified in their new of their being on the surf ace/ and conse- 



surroundings. Locomotion and breath- quently their respiratory systems are not 



ing, either one or both of these functions, as greatly modified as in many of the in- 



are, as a rule, very different in land and sects living beneath the surface. It must 



water insects. be borne in mind that an insect breathes 



The variety of aquatic insects, if we by means of the air which enters the body 



consider only the adults, is not great by small openings and is led by means of 



when compared with the land insects. But tubes, which become very finely divided, 



when we compare fresh and salt water like veins, to all parts of the body. By 



forms it is surprising how few kinds there means of contractions and expansions of 



are which live in the sea, in spite of its the body of the insect, the air within these 



vast area and great food supply. So few tubes is caused to circulate, and thus im- 



are the insects found in the sea, or other pure air is driven out and a fresh supply 



salt waters, that, to most of us, to speak is pumped in. 



of aquatic insects only calls to mind fresh Two of the commonest of these surface 



water forms. We shall, therefore, refer dwellers, so well known to the small boy 



almost wholly, to fresh water forms. Let who frequents ponds and streams, are the 



us consider briefly a few examples of Whirligig-beetles or Lucky-bugs, and the 



these. long-legged Water-striders or Water- 



We may distinguish two general skaters. 



groups, according to their special habitat. The Whirligig-beetles are easy to rec- 



Belonging to the first group are those in- ognize on account of their characteristic 



sects which frequent, primarily, the sur- circular gyrations when disturbed, and by 



face of the water. These forms which their habit of associating in large numbers 



breathe air directly, and not air dissolved in quiet places. When one of these 



in water, as is the case with many other groups is disturbed they exhibit such ac- 



water insects, must be kept dry and be tivity that they well deserve their name, 



able to maintain their position on the sur- "Crazy-bugs." The eyes of these beetles 



