Sunday, November 11, 2012

Yeah, it's got a Hemi.

Red-Cross Shield Bug (c) John Ashley
Red-Cross Shield Bug (Elasmostethus cruciatus)

Our descriptive names for colorful bugs don't always tell us what's under the hood.

The cross of red on the back of this one (above) gives it the common street name, "Red-Cross Shield Bug" (Elasmostethus cruciatus). The family name, "Shield Bugs," refers to the shield-like body shape, which comes in a variety of colors and patterns. Shield Bugs are also known as "Stink Bugs" for the foul-smelling liquid produced in glands between the first and second pair of legs, oily exhaust that's used to tell predators, "Back off!"

Shield Bugs belong to the insect order, Hemiptera, which is Greek for "half" (hemi) "wing" (pteron). The front half of each fore wing is thick and leathery while the back half is thin and translucent.

So yeah, it's got a hemi, two of them in fact - a pair of hemi translucent wings.

But hidden under the hood in some Shield Bug species (and only in the females), there's also a pair or two of dual mods called, "Pendergrast's organs." These specialized organs are are still somewhat of a mystery to us, but they seem to serve at least two very different functions. They might emit female pheromones to rev up and attract nearby males. But mostly, these organs are used to individually coat each egg with a noxious, liquid coating to help protect it from predation.

Pendergrast's organs are small glands that pipe their chemical concoctions through microscopic pores, which lead to round depressions in the lower abdomen. Males don't have them and, in Shield Bugs, they are only found in some species. The presence or absence of these organs appears to dictate whether or not members of the species provide maternal care. That is, whether the females will abandon her eggs or stay close and guard over them.

After each egg is laid, the modified female repeatedly brushes her hind legs against the Pendergrast's organ, and then taps her legs on the egg. She repeats this behavior 5-10 times for each egg, for a total of 30-60 seconds. Those Shield Bug species that coat their eggs with a chemical deterrent do not provide any further parental care. They abandon them. But for those species lacking the organ, and thus lacking this chemical deterrent, the female will stay put to brood her eggs and protect her young after they hatch.

This behavior leads us to yet another name. All Shield Bugs are Stink Bugs. But some species are also called "Parent Bugs" because they provide maternal care to make up for not having Pendregrast's organs. The males get lumped in as Parent Bugs, too, even though they're really just deadbeat dads.

All of which just goes to show that you shouldn't judge a bug by its color - or by its name.