Trillions of insects over millions of years have fallen into ponds, streams, rivers, lakes and puddles. Even though all of them have a waterproofing wax covering to their bodies (cuticles) they will eventually drown if they are not taken by aquatic denizens from below or swooping flying beasts from above. Either way this is a large potential food supply. All those that have fallen don't sink because of water tension. Water Striders have exploited the physics of water when exposed to atmosphere by 'skating' to mired prey and sucking them dry. You might ask how they avoid being taken by predators from above and below. Undoubtedly some leave the gene pool in this fashion. The underbody is pale-coloured which may make them less obvious when viewed from below against a sky background. This 'skater' has spied another smaller bug 'skater' from further down the food chain. Like the Water Strider the Riffle Bug has an elongated second pair of legs for 'rowing'
Limnometra sp. TBC (stalking riffle bug Perritopus sp.) Penang Island Malaysia WL 14.0mmDavid & Fleur Knowles, from