Bugs in the Pool

There you are. A hot summer day, the water in your backyard swimming pool has warmed to a comfortable level, and you have the opportunity to just float around on an air mattress with your legs dangling in the water to keep you just cool enough. You are relaxed, you are getting drowsy……and suddenly something crawls on your leg - UNDER THE WATER!! So much for that quiet, cozy mood you were forming.

How on earth could bugs get into your swimming pool? They certainly didn't come from the garden hose. They didn't swim in from the filter. But there they are, swimming around on or in your backyard pool, looking for all the world like they belong in the water. Well, that's because they do. They probably are some of the many kinds of insects that live in water, a habitat we refer to as "aquatic", and just because they find their livelihood in the water does not necessarily mean that they are restricted to that environment. In fact, many of the species are excellent fliers once they reach the adult insect stage.

There are two principal groups of aquatic insects:

  • Beetles - water scavenger beetles, predaceous diving beetles, whirligig beetles, and some more obscure kinds.
  • Bugs - water striders, backswimmers, water boatmen, and giant water bugs (lovingly given the nickname of "toe biters")

All of these insects I have just mentioned are predators, feeding primarily on other insects that either live in the water with them, or accidentally fall into it. Just like the fish that swims slowly along, one eye on the surface of the water in case a bug lands on it, so are the insects always watching for their next meal. They still must breathe air, and thus make regular trips to the surface to replenish this need, but they can spend most of their time underwater, often hiding under rocks on the bottom in an effort to keep from becoming, themselves, a food source for the larger predators around them.

Since most of these aquatic insects are equipped with well developed wings, they can fly. The reason for leaving the comfort of their pond or creek is probably the instinct that most animals have to disperse, expanding their range to ensure their species survives. Some of these critters like to fly at night, and may be attracted to porch lights or reflections of light off your pool, and they home in on this potential new habitat.

Other species are day-flyers, and it again is the reflection of the shimmering water that draws them to your pool. In fact, any shiny reflection may signal "Water!" to them, as they fly by, and down they dive. You may frequently find some of these poor bugs laying dead on your car on a hot summer day, victims of the deception of your shiny paint job and a fry-pan hot metal as they dive onto it.

The Beetles

One of the largest of these aquatic bugs that you may see around lights or in your pool is the Giant Water Scavenger Beetle (family Hydrophilidae). It is common to find these 2 inch long beetles scrambling around on the parking area of car dealers, where the bright mercury vapor lights overhead - so common at such locations for the added security - are like magnets to these beetles. Of course, a bug this big is a pretty decent meal for birds, so you also may find crows or other insect feeding birds gorging on this unexpected feast.

A close look at the physical makeup of this bug, and most others that spend their time in water, shows a streamlined appearance, perfect for gliding through the water with minimum effort. Their legs taper down to points rather than clumsy claws, and often the front legs are aimed in toward each other, the better to grip whatever foods they may find. The Water Scavenger Beetles are predators only as the larvae. The adults, as their name implies, feed on whatever kind of nutritious debris they can find in the water or on the bottom.

This family of beetles has dozens of different species in it, and another family called the Predaceous Diving Beetles (family Dytiscidae) has similar members that commonly find their way to swimming pools. The beetles are about 3/8" long, shiny black, and swim slowly underwater to find their way around. Both of these families of helpful beetles are harmless to people, but they may be large enough to actually attack and feed on small fish. Both adults and larvae are predators, and the larvae are referred to as "water tigers".

A third family of beetles might also be found in the pool, as they are extremely common in many aquatic habitats. This curious group is called the "whirligig" beetles, due to their habit of staying on the surface of the water where they can be seen spinning rapidly around in circles, often in groups of several beetles. Again, they are small beetles, and often very dark colored or black. Supposedly, when handled, some species will exude an odor similar to pineapple. I don't know if they taste the same.

A rather fascinating curiosity with the Whirligig Beetles is that they actually have 4 eyes. There is a pair of eyes on each side of the head, one eye facing down and one eye facing up! Since they swim on top of the water this gives them the best possible chance of seeing food below in the water or above as it falls. They also are more exposed to predators, and the chances of spotting lurking fish or birds is improved. It must work - they've been around for millions of years.

The True Bugs

One of the Orders of insects is referred to as the "true" bugs, and this is the group called the Heteroptera (formerly Hemiptera). It contains such well-known members as Stink Bugs, Box Elder Bugs, and Assassin Bugs. It also contains four common families of aquatic species, all of which are predators on other critters they may find in that watery environment, and which often fly about in the daytime and may end up in your back yard ponds or pools.

The first of these is a huge, dramatic group called the Giant Water Bugs. although I have never spoken with anyone who has suffered from the event, another name for these 1 inch to 4 inch long beasts is "Toe Biters". They have a beak for a mouth, and on the larger species, which may be found in Arizona and other southern habitats, that beak could be ¼" long. They use it by impaling their food and, while gripping with their inward-facing front legs, suck out the innards of their prey. While they certainly cannot view humans as food, they might retaliate by biting if they got stepped on when someone is wading in shallow water.

In some countries of Southeast Asia these massive bugs are viewed as an excellent food, and the common name of Rice Bugs is applied to them. I spoke with people in Thailand years ago, and asked them how they consume the bugs. The reply was that they either dry them and grind them up as a flavoring, or just stick the bug in their mouth and munch!! Everything tastes better when it's fresh.

Another member of the Heteroptera is one we've all seen and enjoyed as children, and this is the group called Water Striders - family Gerridae. They may be around one inch long, with very long legs, and have the remarkable ability to stand on top of the water, sliding around on it very quickly as they seek out their food. The surface tension of the water is strong enough to enable these light, leggy bugs to keep from breaking through and sinking.

The other two families are the Water Boatmen (family Corixidae) and the Backswimmers (family Notonectidae), given that name because they actually do swim upside down, just as though you were doing the backstroke yourself. These are much, much smaller than the Giant Water Bugs, and more likely to be the ones in your pool. I work near the Sacramento River in California, and often find dozens of them dead on top of my car in the summer, victims of the deception we described earlier, in which they thought my car just had to be a pond, due to the way it reflected the sunlight as they flew by.

Water Boatmen and Backswimmers feed in the same way that the Giant Water Bugs do. In fact, pretty much every member of the Order Heteroptera feeds by means of a sucking beak for a mouth. They jab their beak into their food and suck out the juices. My daughter had some friends over for a swim one time, and one of the girls picked up a Backswimmer that happened to be in our pool. (I'm pretty sure I didn't suggest it to her.) However, the bug was frightened by this sudden removal from the water, and it poked it's beak at her skin, causing slight pain and a tiny red mark. This 10 year old wasn't in any serious danger of having her innards sucked out, but it startled her nonetheless.

So, you might just have visitors in your pool. Of course, there could be a lot of bugs and other animals that just fall in by accident. We've pulled snakes out of our own pool a few times. But there are those bugs whose lives are meant to be in water, and they'll find a way to tolerate the chlorine and the other monsters swimming around for a few days, and then move on.