BIOLOGY OF GIANT WATER BUGS

The giant water bug that had the good fortune to be rescued by me, rather than being left to get run over on the road turned out to be a specimen of Lethocerus americanus. This is probably the most common species of giant water bug found in Manitoba, although information about them is spotty. I wasn't able to track down exactly how many species we have, but there's likely at least two. Giant water bugs belong to the Family: Belostomatidae and fall within the Order: Hemiptera (the bugs), of the Class: Insecta (insects). There are perhaps 150 species of giant water bugs worldwide with the largest being up to 150 mm long (6 inches)!

The habitat of giant water bugs in Manitoba includes ponds, marshes, lakes and slow moving rivers and streams. Lethocerus americanus is widely distributed in North America, but as with many creatures, its exact range in this province isn't known. They are certainly found throughout most of the southern half of the province. If you northern Manitobans have any information on the subject, please let us know.

Adult giant water bugs are most often encountered by people when they are out of their natural element, the water. Adults often fly around, perhaps searching for other water bodies to colonize or for mates. They fly mainly at night and it's thought that they use light sources (before humans this was the moon or stars) as beacons to orient their flight. With the advent of electric lights, giant water bugs, and a lot of other insects, (moths for example) faced a hitherto unknown situation, light sources that were not at a fixed point in the sky. These light sources were close enough that they appear to move as the insect flies, unlike the distant moon or stars. The net result of trying to navigate using a point of light that you think should stay fixed, but which in fact isn't, tends to be flight that spirals in toward the light. Water bugs and other insects may not be "attracted" to lights as much as they are disoriented by them and once too near the light can't find any other beacon to navigate by. In the end they become exhausted from aimlessly flying around the light and end up lying on the ground below street lights on roads or parking lots.

In late spring or early summer the adult bugs mate and the female glues her eggs on the stems of emergent vegetation or other structures just above the water's surface. The male remains nearby to protect them and to keep them moist by periodically crawling out of the water and over top of the eggs. The young are called nymphs and hatch in about 2 weeks. The nymphs resemble the adults and go through 5 developmental stages, shedding their skin to move from one stage to the next. This is known as "simple" metamorphosis. In the "complete" metamorphosis of butterflies and other insects, larvae don't resemble the adults and there is a resting or pupal stage prior to emergence of the fully formed adult. Adult water bugs overwinter in water bodies. (I wasn't able to find out when the last moult from nymph to adult occurs in Manitoba. Does anybody out there know? If so, please drop us a line.)

As larvae, giant water bugs obtain oxygen through their cuticle (skin), but the adults must breath air directly. They do this, and remain under water, by means of a snorkel-like appendage at the base of their abdomens. This tube allows for the exchange of air from the atmosphere to a bubble of air trapped under the wings. Air enters the insect's body through holes, called spiracles, in the abdomen.