26 



INSECTS 



are very peculiar in that each eye is di- 

 vided into an upper and lower part. Thus 

 the insect has practically an upper and 

 lower pair, one adapted for sight at the 

 surface, and the other for vision under 

 water. 



The Whirligigs do not seem to be very 

 particular about their food, as they wall 

 accept both live and dead insects which 

 fall into the water, and even under some 

 circttmstances will feed upon plants. 

 \\'hen a beetle plunges beneath the sur- 

 face, as he often does when frightened, 

 he carries down a small bubble of air be- 

 tween the ends of his horny wings and 

 the tip of his body. On account of his 

 body being lighter than water it takes 

 some effort to dive, but none to rise to the 

 surface. The two hind pairs of legs 

 which are used so much in swimming are 

 very much flattened and plate like, mak- 

 ing excellent paddles, as is shown by their 

 exceedingly rapid movements. 



The Water-skaters, or Striders, prefer 

 quiet waters, as do the Whirligigs, but do 

 not have the decided social disposition, 

 shown in the latter to such a marked de- 

 gree. These Skaters, on account of their 

 long legs and short bodies, are the "Daddy 

 long-legs" of the water.' These character- 

 istics and their habitat make them easy to 

 recognize. They are nervous, active in- 

 sects in their movements, jumping and 

 skimming about on the surface with but 

 little show of grace and ease as compared 

 with the ordinary graceful curves of the 

 whirligigs. Their food habits are very 

 similar to those of other surface insects, 

 that is, dead and dying insects found 

 floating on the water. But their method 

 of taking food is quite different from that 

 of the Whirligigs, because of the great 

 difference in the structure of their mouth 

 parts. The Whirligig, being a beetle, has 

 the typical biting mouth parts, while the 

 Strider has a slender beak or proboscis, 

 by means of which it sucks the juices 

 from its prey, as do other bugs. The fore 

 legs are used to seize the prey and bring it 

 within reach of the beak. The middle and 

 hind pair are used for rowing over the 

 surface, the latter pair, primarily, foV 

 steerage, the fine hairs on the legs mak- 

 ing it possible, as mentioned before, to 

 make use of the surface tension. Large 

 dimples are formed on the surface of the 



water where the feet touch it. One would' 

 hardly expect it possible for an insect 

 standing on the surface of water to get its 

 feet dirty, yet the great care which they 

 give to cleaning their feet clearly shows 

 that dirt is of common occurrence, even 

 there. The white or gray color on the 

 lower side of the body is due to the re- 

 flection of light from minute hairs which 

 cover the surface, and keep the insect dry 

 even when submerged. 



The marine relatives of our Striders 

 have some curious habits. Some of them 

 live out at sea, hundreds of miles from 

 land, where they are thought to feed upon 

 the dead bodies of small animals. When 

 the surface of the sea is calm they glide in 

 colonies quickly over the surface, showing 

 great skill in diving, but if the sea begins 

 to become agitated they immediately dis- 

 appear from the surface. 



Perhaps the most remarkable liabit 

 which a surface insect has is that pos- 

 sessed by some of the allies of the Skaters,, 

 which not only swim in the water, but 

 actually run on the under side of the sur- 

 face film. It would be very interesting to- 

 know how such a habit was acquired. 



Another interesting group of insects 

 are those which breathe air, as the surface 

 film insects, yet seek their food below the 

 surface. These insects are compelled, on 

 account of their air-breathing habits, to- 

 repeatedly visit the surface or communi- 

 cate in some way with a fresh supply of 

 air. 



We have two families of the large-sized 

 water beetles, common in our ponds and 

 streams. The Predaceous water-beetles 

 and the W^ater-scavenger beetles. These 

 are easily recognized, because in the for- 

 mer, the antennae are thread-like and not 

 enlarged at the tip. While the members 

 of the Water-scavenger family have the 

 antennae enlarged or club-shaped at the 

 tip. The Predaceous water-beetles are 

 often quite common under electric 

 lights, where they have been at- 

 tracted by the intense light. Their 

 large size and clumsy movements, 

 when out of water, attract attention. But 

 when seen in water their skill as swim- 

 mers is in striking contrast to their awk- 

 ward movements made on land. The hind 

 legs are flattened and very powerful, the 

 surface being increased by a fringe of 



