It’s not unusual for gardeners to find large caterpillars of the Tobacco Hornworm munching on their tomato or pepper plants. Hornworm caterpillars get their name from the horn-like structure at the back end of the insect and while many species of hornworm caterpillars are known from Wisconsin, the tobacco hornworm is one of the largest and can reach lengths of over 3″. If all goes well, the caterpillars eventually transform into large, grayish sphinx moths with a series of yellowish dots on the sides of the abdomen.
However, tiny parasitic wasps will sometimes kill a caterpillar before it can turn into an adult moth. Female Cotesia wasps inject eggs into a tobacco hornworm caterpillar and the developing wasp larvae live as internal parasites. At a certain point, the wasp larvae have matured and move to the outside of the caterpillar to spin silken cocoons and transform into adult wasps. Biological control in action!
Every once in a while I get a report of a miniature “walking stick”. We do have a few different species of walking sticks in Wisconsin, but the adults are typically 2″ – 3″ long. We do, however, have some tiny insects called stilt bugs that pop up from time to time during the warmer months. They’re often seen on flowers but can also be found at porch lights. I usually find a few each year, although they can often be overlooked due to their small size.
At a quick glance, these insects can resemble small walking sticks but some key differences exist. First of all, stilt bugs tend to be quite small: usually around 1/2″ long. Their antennae are also very long with relation to their body and have swollen tips; the antennae of our walking sticks lack these swollen tips. A final difference is in the mouthparts of these insects. Our walking stick species chew on the leaves of oak trees and other plants using mouthparts that function like scissors or pliers. Stilt bugs consume a liquid diet of plant fluids and have a specialized “straw-like” mouthpart to suck up fluids. In the image below, the straw-like mouthparts can be seen curling backwards under the body from the head.
Many folks are familiar with crane flies, which like to hang around porch lights in the summer and resemble monstrous mosquitoes (luckily, they don’t bite). From a quick glance, the large insect below generally resembles a crane fly, but has a rather striking coloration to its body. Is it simply a crane fly dressed up in a tuxedo for a luxurious night out on the town? Not quite.
It turns out that it’s from a different family of insects called the phantom crane flies. The particular species in this image is Bittacomorphaclavipes. Not only does this species have a unique black and white pattern, but segments of the tarsi (“feet”) appear swollen. These insects occur in the eastern US (including Wisconsin) and are associated with wetlands but aren’t encountered often.
One of those unusual insects that seems like something out of a science fiction movie is a bot fly. These insects are parasites of other animals, where they live beneath the skin as larvae. There are a number of species out there that affect large mammals such as cattle, sheep, and caribou. There’s also a species called the human bot fly (Dermatobia hominis), which is known from tropical locations. Around Wisconsin, we have some species in the genus Cuterebra that attack rodents and rabbits. As adults, the rabbit bot flies resemble large, black and white bees with red spots on their eyes. They’re rarely seen, but a photograph recently came in from Madison, WI.
Like deer hunters going years without seeing that one “big buck”, entomologists have their own, albeit smaller, trophy to chase after: a male eastern dobsonfly (Corydalus cornutus). Males of this species have intimidatingly large mandibles, which can be over an inch long. I’ve never seen one live myself, but have had several pictures come in to the diagnostic lab this summer. The larvae (called hellgrammites) live in fast moving rivers and streams. The adults are strong fliers and can be attracted to lights at night.
One of the most unusual bees I’ve ever seen was brought in by our fruit crop entomologist earlier today. Its behavior had been described as somewhat “fly-like”, although the abdomen had a color pattern that screamed “yellowjacket”. It was hairy like most bees, but possessed some unusual hook-like appendages from the tip of the abdomen. After some digging, I was able to identify the species as Anthidium manicatum, commonly known as the “European wool-carder bee”. It happens to be a European species that was introduced to the US back in the 60’s and is now widespread. The species gets its name because females collect hair-like fibers from plants to line their nests.
It’s that time of the year again. Much to the dismay of gardeners and landscapers in Wisconsin, the first reports of Japanese Beetle adults came in last week from the La Crosse area. Additional reports from Dane, Racine, Sauk, and Rock counties have trickled in over the last few days. Despite the deep frosts reported last winter, the soil-dwelling grubs managed to survive just fine and the adults are popping out as if it were a typical year. Based on our history in the state, we’ll likely be seeing the Japanese beetles until early September.
A recent image came in to the lab from the Wausau area of an adult elderberry borer (Desmocerus palliatus). It gets its name from the larval stage which lives inside the stems of elderberry plants and bores down to the roots. These beetles are members of the long-horned beetle family (Cerambycidae) due to their long antennae. The elderberry borer happens to be one of our most distinctive species, although it isn’t spotted often. It was even featured many years ago on a 33 cent US postal stamp.
One of my favorite submissions to the lab came in recently from Waupaca County, WI. The species is known as the Goldsmith Beetle (Cotalpa lonigera). It resembles a large May/June Beetle or the Grapevine Beetle. The neat thing about this particular species is the brilliant metallic, golden color of the head and pronotum, which reminds me of the scarabs of ancient Egyptian lore. It’s an uncommon species known from the eastern half of North America, and is apparently associated with woodlands.
“What’s Crawling in the Lab?” is a blog featuring short stories, pictures, and highlights from the UW-Madison Insect Diagnostic Lab. Topics range from the insects most commonly diagnosed in the lab to emerging arthropod pests and unique and bizarre cases from the lab.
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