In our last post about insect names we discussed some of the pros and cons of common and scientific names. In this post, I want to walk through a case study that will illustrate in more detail how common name conventions work and why it can be important to get names right.
As promised earlier, I want to discuss the distinction between a water bug and a waterbug. If you recall from that post, a name that follows the formula “descriptor” [space] “name” is an accurate name for the animal, whereas a name that follows the formula “descriptorname” without a space indicates a species that does not actually belong to the group the name suggests. With water bugs and waterbugs, we’ve got one of each, suggesting that one truly is a bug and the other is something else. So what are these two insects, and does the distinction between them matter?
Let’s start with a quick description of waterbugs (the name mostly applies to Blatta orientalis and Periplaneta americana, two species of cockroaches). These species of cockroach earn the moniker of “waterbug” for being common in damp crawlspaces, basements, drain pipes, steam tunnels, and other consistently-wet locations. All cockroaches belong to the order Blattodea and are not true bugs; they have chewing mouthparts, and the front wings (if present) are tough and leathery along their entire length.
Now let’s compare to water bugs (superfamily Nepomorpha). “Water bugs” could be used in a broad sense to refer to water scorpions (family Nepidae), backswimmers (family Notonectidae), pygmy backswimmers (family Pleidae), water boatmen (family Corixidae), creeping water bugs (family Naucoridae), ferocious water bugs (subfamily Belostomatinae), and giant water bugs (subfamily Lethocerinae), but I prefer to use the name more specifically for the ferocious water bugs and giant water bugs (family Belostomatidae). These insects can have some superficial similarities to the cockroaches described above: both are dark colored (though water bugs are usually brown while waterbugs are closer to black), both are flattened, and both may have wings with a fairly leathery texture. However, there are also some major differences in appearance. As true bugs, water bugs have a hard, shell-like wing base and a membranous wing tip on wings that reach to the tip of the abdomen, while waterbugs have uniformly leathery, heavily veined wings that are either short triangular wing buds (females) or stubby wings that cover about half the abdomen (males). Water bugs have extremely short antennae that are tucked into grooves on the underside of the head, making them look like they lack antennae entirely, while waterbugs have long, threadlike antennae. Water bug mouths are relatively short, sturdy, needle-sharp beaks (piercing/sucking beaks are another true bug trait) while waterbug mouths are robust chewing mandibles. Lastly, water bug legs are specialized for their watery habitat; the rear four legs are flattened and paddle-shaped, with fringes of sturdy bristles that complement the oar-like structure of the leg, while the front legs are adapted for grasping, like a less spiny version of a praying mantis’s legs. The waterbug’s legs, on the other hand, are typical spiny cockroach legs adapted for walking and running.
The differences between waterbugs and water bugs are not limited to their appearances. Waterbugs exhibit some typical cockroach behaviors, scurrying through nooks and crannies, retreating from light, and scavenging whatever crumbs or organic matter they can scrounge up. Waterbugs are one of the top pest cockroaches that Guardian combats, and between causing allergies and contaminating food and living spaces with nasty bacteria they are a legitimate health hazard. Water bugs, on the other hand, are fierce aquatic predators. Able to breathe through short snorkel-like breathing tubes at the tip of the abdomen, they lurk motionless on aquatic plants or debris in ponds, lakes, and slow areas of streams with just the tip of their abdomen protruding above the surface. As youngsters, their proximity to the water’s surface and savage appetite make them an excellent predator of mosquito larvae; as adults, they mostly feed on insects and crustaceans but can also take small fish, frogs, salamanders, snakes, and turtle hatchlings. They are clumsy walkers, but swift swimmers and strong fliers that are attracted to lights at night. Because they find new ponds by detecting the polarized light that reflects off a calm water surface, and polarized light reflects off almost any flat surface, they are commonly found stranded in large, well-illuminated parking lots on warm, humid summer nights.
On one hand we have the waterbug, a household pest that mechanically vectors diseases and contributes to allergies and asthma, and on the other hand we have the water bug, a fierce outdoor aquatic predator. That space in the name is very important, because the names are far more similar than the actual insects are. A major component of IPM is identifying the pest (including whether or not it actually is a pest) and modifying the environment to make life more difficult for the pest. For waterbugs, which are common pests, cleaning up water leaks and food sources are good first steps in an IPM program to slow their population growth. For water bugs, which may be beneficial insects, using warm-colored LEDs1 and not leaving lights on unnecessarily may keep the bugs in their wetland habitats munching mosquito larvae rather than divebombing your parking lot.
1Justice, M. 2016. Light pollution and insects: insect attraction to various types of residential lights. AAAS Annual Meeting, poster presentation