Stink bugs are common insects that look sort of like beetles. However, stink bugs are only distantly related to beetles and belong to a separate group: the Pentatomidae family in the order Hemiptera (which also includes Boxelder Bugs). There are thousands of stink bug species around the world. Most are some combination of brown, green, and red/orange in coloration.
Hemiptera means “half-wing” in Greek and refers to the fact that the wings of insects in this group each have a thick, leathery base and a softer, translucent tip.
The structure behind the head of a stink bug, the pronotum, is generally broad and angular, making the bug look like it’s sporting shoulder pads from the 1980s.
When threatened, stink bugs release irritating, strong-smelling chemicals from glands on their thorax (the middle section of an insect’s body). These chemicals may have other uses besides defense, such as mate attraction.
The bug in the photo above– found in my backyard in Portland and which the folks over at Bug Guide tell me is probably Banasa sordida– sprayed me with its chemical funk during our little photo shoot. The smell wasn’t disgusting, but it was very pungent and “medicinal.” It lingered on my hands even after I washed.
I can imagine that such a blast of stink bug defense chemicals would be most effective on small predators, such as a spiders, frogs, and lizards.
Another stink bug trait that is easy to see is the triagular, shield-shaped structure between the wings on the bug’s back. This is called a scutellum (pl. scutella). Inside the scutellum lies a muscular pump that helps keep blood (insect blood is called hemolymph) supplied to the wings during flight. This circulatory organ is like an accessory heart for the wings.
Like all hemipteran insects, stink bugs have piercing mouthparts. Many stink bug species pierce plants to feed, while other species are predatory. Some herbivorous stink bugs are agricultural pests. For example, the Brown Marmorated Stink Bug is native to eastern Asia, but was introduced to North America in the late 1990s and has been causing trouble with fruit crops ever since.
Stink bugs that live in cool temperate regions are dormant in the cold winter months. The Rough Plant Bug (Brochymena species) in the photo above is emerging from a dead tree (see my post on ‘snags’) on a sunny spring day in Washington State. I found several other bugs peeking out from cracks in the tree, which probably served as the bugs’ winter shelter. It is common for bugs to congregate like this in the winter.
Stink bugs and Boxelder Bugs (which are not in the stink bug family, although they are in the order Hemiptera) may also find their way into the nooks and crannies of your house in the winter. If they do, you’ll have a great opportunity to get a close look at these fascinating animals.
The diagram below labels the body parts of a stink bug:
A: head; B: thorax; C: abdomen.
1: claws; 2: tarsus; 3: tibia; 4: femur; 8: compound eye; 9: antenna; 10: clypeus; 23: laterotergites; 25: pronotum; 26: scutellum; 27: clavus; 28: corium; 29: embolium; 30: membrane.
The diagram above was created by Giancarlodessi and is available in the Wikimedia Commons.