The star of today’s show is one of several stink bugs that the BugLady photographed during the Stink Bug Summer of 2016. A pair of stink bugs was featured a few months ago, one a carnivore, and the other an herbivore. The herbivore, the Twice-stabbed Stink Bug, includes a few agricultural crops on its menu but is not generally considered a big pest. The star of today’s show is an herbivore that on the Most Wanted lists of Extension agencies everywhere.
Stink bugs are a long-time favorite of the BugLady. They belong to the family Pentatomidae, which is in the order Hemiptera, and they have the mouthparts to prove it—a sharp-tipped tubular “beak” that allows them to pierce their prey, inject a tissue-tenderizing chemical saliva, and then suck out the resulting goop. They are solid, no-nonsense bugs whose name is well-deserved, being endowed (at the other end) with glands that manufacture chemicals which, when sprayed, make their predators think again (alas, not all are deterred). They come in a rainbow of colors and even the nymphs are pretty.
Brown Stink Bug
Brown Stink Bugs (Euschistus sp.) feed on leaves, stems, flowers, seeds, nuts, and fruits of a variety of plants, both wild and domestic. In fruit crops, their injected saliva may cause chemical damage, and their piercing may cause mechanical damage (holes) or cosmetic issues (scars on fruit)&mdashin fact, some brown stink bugs are called “cat-facing insects” because of the cat-face-shaped scars that are left by their browsing.
The BugLady isn’t going to go any farther out on a limb than genus Euschistus this time (there 20 Euschistus species in North America), the nymphs are hard to tell apart, and she probably has several species here. According to bugguide.net, “One thing that all the Euschistus spp. have in common, besides being brown, is a vague, barely visible dark patch in the center of the scutellum (the triangular area on the middle of the back) and a smaller matching spot on each upper wing half. These look more like smudges than markings, and are more visible in certain light conditions and at certain angles.” Euschistus servus, a ubiquitous brown stink bug that is called “The” Brown stink bug in some publications, will serve as a poster bug here.
Euschistus servus is a generalist feeder that has been recorded on about 70 different host plants in 25 plant families and that, in Wisconsin, is unwelcome on soybeans, corn, alfalfa, and fruit. Add cotton (to the tune of millions of dollars annually in damage and control), sorghum, pecans, peaches, and tobacco farther south. They produce two broods per year (more in Florida); the first brood typically feeds on wild plants and the second tucks into agricultural/garden crops. In the lab, one Euschistus was seen eating the caterpillar of the equally unpopular cabbage butterfly, which could confuse its bad-guy image. One or another subspecies of Euschistus servus can be found across North America.
Like all Hemipterans, brown stink bugs develop by simple/gradual metamorphosis, going from an egg, to a nymph that looks pretty much like an adult and that adds adult body parts as it grows, to an adult. Female brown stink bugs lay their eggs in clusters of 15 or more; the eggs hatch in a week or so, and the nymphs stay together briefly before dispersing. It takes them about five weeks to grow and molt through four or five instars and reach adulthood. Check the site Featured Creatures for some great pictures of life stages. Brown stink bugs are around from late spring through the start of fall; they overwinter as adults under debris, old vegetation, tree bark, etc. and emerge when the air temperatures hit about 70 degrees. Adults are strong—and often noisy—flyers.
Of the million or so species of insects that we know of today, around 20% are believed to send some sort of signals through the substrate (whatever they’re sitting on). Stink bugs, it turns out, are pretty chatty. Researchers Andreja Kavcic, et al. studied the communication system of Euschistus hero, a Brazilian stink bug. Male and female E. heros can send out low frequency signals by vibration (rubbing body parts together—stridulation), tremulation (planting their feet on the substrate and vibrating part or all of their body), percussion (tapping on something with their feet), and buzzing (vibrating their partly-opened wings). The tremulatory signals can travel through the air and be picked up by stink bugs on nearby plants, which increases the audience. Messages are received via vibration detectors on the legs and by highly sensitive hair sensilla (sensors) on the exoskeleton. These signals are part of courtship (they call, and later sing duets).
Male and female Euschistus servus use vibrations to make contact and they sing during courtship. Males have four calls/songs, and females two, and different songs are used as courtship proceeds.
For an appropriately-named paper in insect vibrations, see What, When, How – Vibrational Communication.