During the winter months, I often get reports of intimidating-looking, but harmless and quirky wasp-like creatures known as “wood wasps” (Family Xiphydriidae). What makes them quirky?—They’re basically the bobbleheads of the insect world, which always reminds me of going to baseball games as a kid.
Having “wasp” in the name can evoke a certain amount of anxiety, and you can already guess that wood wasps are related to the yellowjackets and paperwasps of late summer. However, the wood wasps belong to an early branch within ant/bee/wasp group (the Order Hymenoptera) and lack the anatomical structures and ability to sting.
Wood wasps have a distinct appearance, so once you’ve trained your eye, they’ll be hard to miss the next time around. These insects tend to be about an inch long with slender, dark-colored bodies and orange legs. There are often some pale stripes or patches on or just behind the head and in some cases the tips of the antennae can be pale as well. The most diagnostic feature gives wood wasps their bobblehead status in my book—the bulbous head of these insects is attached by a scrawny “neck” when viewed from the side. You can even imagine it bobbing back and forth, if only a tiny spring were attached.
You might ask yourself, how are these insect bobbleheads active in winter when most other insects are scarce? The answer boils down to firewood. The pale, grub-like larvae of wood wasps live in the wood of dead or dying trees. When these trees are chopped into firewood, we end up hand-carrying the insects into our cozy winter abode. If the wood isn’t used in the fireplace right away, the larvae take advantage of the spring-like conditions and transform into active adults indoors. To those unfamiliar with wood wasps, you can scratch your head for days trying to find the source, but once you recognize them and their origins, moving the firewood to a colder location is the simple fix.
We’re all familiar with phenology—that regular progression of plant and animal life through the seasons—to a certain extent. We might not stop to think about it in detail, but we recognize the crabapples blooming in spring, the fireflies lighting up the nighttime sky in June and July, and the southward flying geese and rutting deer in fall. When you think of the 25,000+ insects in the Great Lakes Region, there’s a rich diversity of seasonal patterns to pick up on. Some insect patterns, like cicadas, katydids, and tree crickets calling during the summer months, are hard to miss—although it can be challenging to decipher exactly who’s making that racket (Hint: here’s your translator). Others are much harder to pick up on unless you’ve been briefed on the subtle clues. For example, take the tiny foreign grain beetle (Ahasverus advena) which conspicuously pops up in unexpected places in August, September, and October.
To the naked eye, these tiny (1/16 inch long) brownish insects can be a bit tricky to see and it’s hard to tell if they’re beetles, ants, or something else. Even to budding entomology students pushing the boundaries of what they can interpret under the microscope, foreign grain beetles and relatives might be jokingly referred to as “little brown nothings” and passed over for easier-to-identify specimens.
Around the UW Insect Diagnostic Lab, foreign grain beetles are one of my favorite samples when they arrive in late summer and early fall as they give me the faintest sensation of what it must feel like to be Sherlock Holmes. Picture a client coming in with a Ziploc bag of tiny brown insects. After a cursory glance and before the specimens even make it under the microscope, I ask, “are you in a new home by any chance?” The standard reply is often along the lines of, “Well, yes—but how did you know?” A quick check under the microscope and the specimen’s identity is confirmed. It’s elementary, my dear Watson.
How is there such a reliable association with an unexpected source: newly constructed homes, where intuition wouldn’t have you expecting insects? The secret to this seasonal pattern lies in understanding the biology of the foreign grain beetle and its relatives. These insects love to feed on fungal spores—often in musty stored grains on farms. It turns out that during the construction of a new home, residual dampness in construction lumber, plaster, sawdust, and other materials can lead to the growth of a trivial amount of mold. Like vultures to carrion, these beetles fly in looking for a fungal smorgasbord. Eggs are laid and entire life cycles can be carried out in the wall void of a new home after the drywall, insulation, and siding are put up.
Fast-forward to late summer and just like clockwork the proud new homeowners suddenly have hundreds of tiny brown beetles crawling out through nooks and crannies, causing immediate dismay. While this can be alarming, these insects are harmless to people, pets, and the home, and are simply a temporary nuisance. As the construction materials lose that lingering moisture, conditions become unfavorable for the beetles and activity drops off over time. Pesticides often aren’t needed as the beetles already face an inevitable demise. Vacuuming or sweeping them up and running a dehumidifier are often the remedy in fall until the dryness of winter puts a final end to the beetle activity.
As National Dairy Month rolls to a close, you might not have realized the connections between insects and the milk, cheese, yogurt, or ice-cream you’ve had in the last month. While you might not think of any association between insects and dairy, the connections are surprisingly plentiful. Some of these links are conspicuous—insect pollinators, for example, play an important role in the production of seeds for growing hay crops like alfalfa. A plethora of caterpillars, beetles, and true bugs can be pests of those same crops and threaten to reduce hay yields. In addition, many flies, mites, and grubs can directly bite, pester or even infest dairy of beef cattle and farmers have to manage these pests to maintain herd health and maximize milk or beef production.
Other connections can be downright bizarre—perhaps the most outlandish link between insects and dairy is a cheese so engulfed in a legal cloud that it has been sold on the black market at times: casu marzu. In Wisconsin we’re blessed with enough cheeses to be the envy of other states, but the thought of an illegal cheese is still mind-boggling.
The cheese in this case, casu marzu, is a soft unpasteurized variety made from goat’s milk. It’s made on the Island of Sardinia in Italy and has a unique flavor developed by live maggots of the cheese skipper (Piophila casei)—making blue cheese seem wimpy in comparison. Cheese skippers like to infest protein-rich materials such as processed cheeses and meats (they’re also called “bacon flies”) and get their name from the ability of the larvae to “skip” or fling themselves into the air when disturbed:
While cheese skippers have a cosmopolitan distribution, you probably won’t encounter these insects unless you add dairy, meats, or other protein-rich materials to your compost pile (which you shouldn’t do). This very composting mistake is the reason why I recently received a cheese skipper sample at the UW Insect Diagnostic Lab.
While most of the cases at the Insect Diagnostic Lab involve fairly common insects, I do also see my fair share of unusual cases each year. One of my favorites from 2015 involved a miniature “bog wasp” from the family Eucharitidae: Pseudochalcura gibbosa. Due to their small size, these tiny (~2 mm long) wasps would simply go unnoticed in most cases––that and the fact that you’d most likely have to be wandering around in a bog to find them. So how exactly did these tiny, easily-overlooked “bog wasps” end up being submitted to the Insect Diagnostic Lab? Simple: a homeowner found several in a second story bedroom of their house. This simply didn’t make much sense, so I knew there must have been a deeper story at play. Whenever I get an unusual case like this in the diagnostic lab, I often have to track down additional pieces of the puzzle before things make sense.
In this case, this particular home was located near Rhinelander, Wisconsin, where there’s certainly an abundance of bogs. As part of their life cycle, the females of Pseudochalcura gibbosa lay eggs on Bog Labrador Tea (Ledum groenlandicum), a common shrubby plant in northern bogs. The eggs spend the winter on the plants and hatch the following spring. However, these wasps aren’t plant feeders, and their presence on Labrador Tea is temporary. What they’re really after are immature carpenter ants (Camponotus sp.) to feed on. After the eggs of Pseudochalcura gibbosa hatch, it’s thought that the wasp larvae hitch a ride on foraging carpenter ant workers back to their nest. Once they’ve dropped off their six-legged taxis in the ant nest, the tiny larvae of Pseudochalcura gibbosa behave much like a wood tick on a dog: they hang off of and feed on carpenter ant larvae and pupae. In some cases, dozens of small wasp larvae may be present on a single carpenter ant larva. Eventually the tiny wasps complete their development and leave the carpenter ant nest to head back to the bog.
Having identified the wasps as Pseudochalcura gibbosa, I was suspicious that a carpenter ant nest was also present in the home and simply hadn’t been found yet. After some detective work, the homeowner eventually confirmed the presence of carpenter ants in the house. With that final piece of the puzzle I had my explanation for how the wasps had hitchhiked from a nearby bog to an upper story bedroom: it’s was all the ants!
In this post, we’re continuing to count-down 2015’s top insect trends in the state. This is the final post in a three part series. Part I (2015’s diagnostic lab statistics) can be found here and Part II (Top Insect Trends Numbers 10-6) can be found here.
With all the headlines about bees, it’s not surprising to see pollinators in the top insect stories again in 2015. Similar to other years in the recent past, honeybees and other pollinators have been facing declines. Unfortunately, Wisconsin saw some of the highest honeybee losses in the country, with over 60% colony loss during the 2014-2015 period. Some good news over the past year has been the development and release of pollinator protection plans. A federal pollinator protection plan was released in May with the goals of reducing honeybee losses, increasing the population of Monarch butterflies, and increasing pollinator habitat. In addition, a Wisconsin pollinator protection plan was announced in 2015, and was just released in January of 2016. Due to the recent declines and their importance to agriculture in the state and nation, pollinators will continue to be in the spotlight in the future.
4) Spring caterpillars
An unexpected insect trend in the spring of 2015 was the surprising abundance of a number of caterpillar species feeding on plants in the landscape. Caterpillar species, such as the humped green fruitworm, speckled green fruitworm, eastern tent caterpillar, forest tent caterpillar, gypsy moth caterpillar, and the euonymous caterpillar are typically present to some extent, although their numbers have been low the past few years. For a number of potential reasons, these species had a great spring and during a period in May and June, caterpillars made up roughly 30% of the cases coming in to the diagnostic lab. Weather patterns (i.e., rainy weather) and natural predators/parasites/diseases can have significant impacts on caterpillar populations each year, so it’ll be interesting to see if we’re faced with a plethora of caterpillars again in 2016. Additional details of this story were featured in a blog post last June.
3) Viburnum Leaf Beetle
In terms of a new emerging pest with the potential to impact a commonly planted landscape shrub, Viburnum Leaf Beetle is near the top of the list. As of late 2014, we only knew of a single infested viburnum bush in northern Milwaukee County, which raised the question: is the infestation small enough to contain and/or eradicate? Some ground truthing this past spring identified many new infestations in SE Wisconsin, in many cases miles from the original site. At the moment, the viburnum leaf beetle seems to be centered around the four county area where Milwaukee, Waukesha, Washington, and Ozaukee counties meet. While this insect only feeds on viburnums (and related plants like Arrowwood), the damage can be significant. It may be some time before this pest spreads elsewhere in the state, but if you have viburnum plants in your yard in SE Wisconsin, be weary! Additional details of this case were featured in a post last June.
2) Brown Marmorated Stink Bug
Populations of the invasive Brown Marmorated Stink Bug increased dramatically in 2015 and this insect takes the overall #2 spot in this list (up from #8 last year). This invasive species was first spotted in the state in 2010, and each year a handful of lone adults have been found in Wisconsin. In the fall of 2015, we had more sightings of BMSB (30+), than in the past 5 years combined! (Spoiler: this trend has continued into early 2016) At this point, the “hot spots” in the state are: Dane County, the greater Milwaukee area, and the Fox River Valley. In addition to being an indoor nuisance pest, BMSB can also feed on and damage a wide variety of plants in home gardens, agricultural fields and orchards. In other places in the country, the first reports of plant damage have typically been noted ~3-5 years after the initial detection of this species. With that said, 2016 could be the year that BMSB really takes off and starts wreaking havoc for gardeners and agricultural growers alike. Additional details of this case can be found in this post from last October.
1) Magnolia Scale
While scale insects have already been mentioned in the “sucking insects” section (#9 on the list), one species in particular, the Magnolia scale (Neolecanium cornuparvum), seemed to stand out amongst all other insects in 2015. This species is often present in low numbers in the state, but the conditions must have been perfect for their populations to explode last year. During the months of June and July, reports of Magnolia scale were coming in on almost a daily basis. Being one of the unusual scale insects, Magnolia scale adults look more like a fungus than an insect (note the whitish blobs in the image below). Not only did this bizarre looking species pummel Magnolia shrubs and trees in many parts of the state, but the honeydew produced by these insects rained down below, attracting ants and yellowjackets and leading to the growth of unsightly black sooty mold. A number of predators, parasites, and diseases typically keep Magnolia scale in check, but with the extremely high infestations noted last year, it’s likely that we’ll continue to see some Magnolia scale activity into 2016. If you experienced magnolia scales first hand, there’s a helpful factsheet available here.
Meet Thylodrias. Kind of sounds like a character from the Game of Thrones. But alas, it’s just an odd beetle about the size of the letter “d” in size ten print.
Although, technically speaking, this one’s not just an odd beetle. It’s more like the king of odd beetles, so much so, that it’s actually known as the odd beetle. Kind of weird for a species belonging to a very common family: dermestidae. Other relatives in the dermestid bloodline include the common hide, larder, and carpet beetles, which occasionally find their way into that old, half-empty box of spaghetti noodles at the back of the kitchen cupboard. However, if you made a closer examination of the dermestid family tree, you’d find that the odd beetle sits alone: a solitary species in its own genus.
By now, you may be wondering: what really makes this one so odd? For starters, it’s a bit infatuated with humans and we only know of the species from human habitations. We even know of specimens from archaeological sites in Iran, but these days it’s most commonly found in museums. It’s somewhat ironic that such an interesting and unusual insect has a history of lurking around the home of the UW-Madison entomology department: Russell Labs1. Like many other museum pests, the odd beetle wanders around looking for a protein-rich meal to feed on. It turns out that Russell Labs is home to plenty of potential food: millions of preserved insect specimens in the Wisconsin Insect Research Collection as well as preserved mammal and bird specimens in the Forestry and Wildlife Ecology wing of the building.
In addition to popping up in weird places, Thylodrias contractus also looks downright bizarre. With the naked eye, an adult female looks more like a bed bug or a small silverfish than a beetle. Technically, the females lack wings and have a larva-like appearance, which is strange in and of itself. Even the males of this species have a peculiar appearance and bear the meekest resemblance to other members of the family. Then there’s the quirky life cycle: developing larvae can go over a year without food. If times are really hard, they can borrow a page from The Curious Case of Benjamin Button and undergo retrogressive molting. With that elasticity in its development, the complete life cycle can vary from several months to several years.
All in all, rather peculiar.
1 Mertins, J. W. 1981. Life History and Morphology of the Odd Beetle, Thylodrias constractus. Ann. Ent. Soc. Am. 74(6): 576-81.