“Ground bee” season is officially here, but before we get any further, let’s clear up a few things about these insects.Ground-nesting bees get a lot of undeserved blame for stings that they simply aren’t responsible for.Despite their claims, many folks have probably never been stung by an actual “ground bee”.Every year I get plenty of calls about “angry stinging ground bees” in late summer, but these are almost always ground-nesting yellowjackets (Vespula spp.). Undoubtedly, if you stumble into an in-ground yellowjacket nest, you’ll be forced to make a hasty retreat from the area as the colony defends itself.But those aren’t bees…
While yellowjackets and bees are related (both belong to the insect order Hymenoptera along with the ants and sawflies), they belong to completely different families.From a standpoint of taxonomic classification,mixing up yellowjackets and bees would be like confusing dogs for cats, raccoons, or walruses (all belong to separate families within the mammalian order Carnivora).We do technically have social, ground-nesting bees that can be ornery if disturbed (i.e., bumble bees), but folks generally recognize bumble bees by their large size and robust appearance.
So what about these other “ground bees”? Most bees (about 2/3 of all bees) are actually ground-nesting species. In the Midwest, we’ve got around 500 different bee species, meaning there are hundreds of ground-nesting species around us.Our common ground-nesting bees include species of: cellophane bees, mining bees, squash bees, longhorned bees, sweat bees, and others. For the most part, these ground-nesting bees are solitary creatures that live alone, although many nests can occur in the same general area as shown in the video clip below. They often prefer sunny, open areas with thin ground cover or bare, sandy soil and can be common in parks and home lawns.
To a certain extent, solitary bees can be thought of as the insect equivalent of “preppers”. Each bee digs her own nest—a small, bunker-like tunnel in the ground, which looks like an ant hill.Not only do the females have to construct these shelters, but she has to gather all of the provisions needed for her young to survive inside—often in the matter of just a few weeks.The female bees collect pollen and nectar from flowers to create a nutritious substance called bee bread, which they place into small chambers (cells) and lay an egg. Once the eggs hatch, the young bees (larvae) have all the supplies they’ll need to grow and develop in their survival bunkers.
Most of these ground bees have a single generation per year.The adult bees are out and active for a short period of time (often a few weeks), before they’re done and gone for the year.When they are active, our solitary bees can be excellent pollinators and can be more efficient than honey bees in some regards.However, their pollination services often go unrecognized and unappreciated by the general public.While news articles regularly sound the alarm about honey bee declines, we should really be much more concerned about the potential loss of our solitary bee species, as they’re more sensitive to disturbances, pesticides, and other stressors.
If you spot ground bees this time of the year, is there any reason for concern? No. Solitary ground-nesting bees are great to have around. Being solitary nesters, these ground bees don’t have a large colony ofadult relatives to defend and they end up being surprisingly gentle and unlikely to sting.Overall, they pose little risk to people or pets.The best thing to do is to simply let them be and appreciate the pollination services they provide.
When the COVID situation reared its head back in March of 2020, I wasn’t sure how it would impact activities at the UW Insect Diagnostic Lab.While there was a shift to handling diagnostics mostly remotely, in the end, 2020’s caseload of 2,533 ID requests was just shy of 2019’s all-time record of 2,542 cases.
With Governor Evers’ Stay-at-Home Order last spring, our attentions were occupied by the unraveling pandemic and caseload at the UW Insect Diagnostic Lab was lighter than usual around that time.However, as Wisconsinites shifted to working from home, it meant spending more time in yards and many Wisconsinites pulled out their green thumbs and established COVID “Victory Gardens”.As a result, the diagnostic lab saw a record number of cases in July of 2020, with close to 600 ID requests that month alone.
Outreach activities of the lab saw a dramatic shift as well.With in-person presentations and workshops off the table, virtual events afforded new opportunities—like a Japanese beetle seminar in July which drew nearly 900 participants. Regular events, like my appearances on WPR’s The Larry Meiller Show also continued through 2020, although I fielded calls from my home’s “reading nook” rather than the WPR studio.
Some invasive pests had big years as well. The viburnum leaf beetle, lily leaf beetle, purple carrot seed moth, and brown marmorated stink bug all increased their footholds in the state. Japanese beetle numbers varied a lot depending on where you were located in Wisconsin. Some areas saw little pressure during droughty periods, while other parts of Wisconsin saw high Japanese beetle activity. Gypsy moths had been quiet in Wisconsin for several years, but increased their numbers last year.I saw a distinct increase of gypsy moth cases in 2020, and I’ll be keeping a close eye on that species in 2021.
Come fall, we saw some stretches of unseasonably pleasant temperatures in October, November, and December.During those periods, multicolored Asian lady beetles—which had been lurking in the background for several years—returned to the spotlight. The multicolored Asian lady beetle activity around Wisconsin was some of the highest of the last decade.Not to be left out of the fun, minute pirate bugs were abundant in some parts of the state and made warm, sunny fall days a little less pleasant due to their biting habits. Speaking of biting insects, black flies were abundant in 2020 and made outdoor activities more challenging in June and July. Mosquito activity varied around the state, although we did see a few cases of the Eastern Equine Encephalitis in 2020.
No two years are the same at the UW Insect Diagnostic Lab and that includes some of the “X-Files” type cases as well.Some of my favorite cases from 2020 include identifying phorid flies from dead radioactive cats (it’s a long story…), a grim-reaper-esque dryinid wasp, several massive black-witch moths from Central America, and a case involving a black widow spider found in a head of broccoli from the grocery store.Never a dull moment at the UW Insect Diagnostic Lab!
With the media craze about “murder hornets” this past spring, I’ve seen a definite increase in reports of Asian giant hornet look-alikes at the UW Insect Diagnostic Lab this summer. Many folks recognize the commonest look-alike in the Midwest, the eastern cicada killer (Sphecius speciosus), which becomes active in July around the time that their prey (cicadas) start emerging. Another look-alike is one that you might not have bumped into before—the great golden digger wasp (Sphex ichneumoneus). Similar to Asian giant hornets, great golden digger wasps are large and nest in the ground, which are reasons why they may be mistaken for the former.
If you haven’t spotted one before, great golden digger wasps can be a bit intimidating in appearance as they can easily be over an inch long. However, their anatomy and appearance are quite different compared to Asian giant hornets. Great golden digger wasps are mostly black with a rusty-reddish color at the base of the gaster (“abdomen”). Their legs are the same reddish color and the black thorax and head possess fine golden setae or “hairs” (hence “golden” in their name). In contrast, Asian giant hornets have distinctive black and yellow stripes on their gaster and a vibrant yellowish-orange head. Great golden digger wasps belong to the “thread-waisted” wasp family (Family Sphecidae) and have a long, slender petiole (“waist”). This isn’t as thin and narrow as the “waist” of the related black and yellow mud dauber (Sceliphron caementarium), but still is quite noticeable when viewed from the side.
In terms of their biology, both Asian giant hornets and great golden digger wasps do nest in the ground, but the similarities end there. The Asian giant hornet is really quite similar to our ground-nesting yellowjackets in terms of their nesting behavior. These are social creatures which start nests from scratch in spring and build up in size over the course of the warmer months. Colonies ultimately die out in fall except for the “new” queens which overwinter. With a large colony of relatives to defend, social wasps can be defensive, especially when colonies are at peak size.
In contrast, great golden digger wasps are solitary ground nesters. Without a large colony of relatives to defend, they’re usually non-aggressive and very unlikely to sting. Stings are only likely if one were to pick one up bare-handed—in which case you might be asking for it! Similar to cicada killer wasps, each female great golden digger wasps excavates small tunnels in sandy soil and provisions them with prey for their young to feed on. In the case of the great golden digger wasp, prey consists of katydids, crickets, and relatives from the “grasshopper” group (Order Orthoptera). Rather than kill outright, the females inject their prey with a paralytic “cocktail” to keep them alive and fresh for their young to feed on—what a way to go! In addition to hunting katydids, adult great golden digger wasps visit flowers and can be beneficial pollinators.
Because they’re unlikely to sting humans, controlling great golden digger wasps is rarely justified and these magnificent creatures can simply be admired. Ultimately, these wasps are strongly associated with sandy soil, so if you see them in your yard every year and would prefer to not have them around, modifying the landscaping may be a long-term option to dissuade them from an area.
Author’s note: As of August 2020, Asian giant hornets have not been found in Wisconsin or anywhere in the Midwest. In North America, these insects are only known from far northwestern Washington state and nearby parts of British Columbia.
See this earlier post for additional details on the Asian giant hornet.
Asian giant hornets have hit the news recently, sometimes going by the name of “murder hornets”. Below are six key things to know about these insects and the situation in North America:
1) What is the Asian Giant Hornet?
The Asian giant hornet (Vespa mandarinia), which is also known as the “great sparrow bee” in its native range (or recently sensationalized as the “murder hornet”) is a wasp species native to parts of southern and eastern Asia. The Asian giant hornet is amongst the world’s largest wasps, with queens approaching a length of 2 inches (typically ~1.5 inches). Workers and males are smaller, but still measure over an inch long. Asian giant hornets have a distinctive appearance with a bright yellowish-orange head, a dark body, and alternating dark and yellowish stripes on the gaster (“abdomen”). This species creates subterranean nests, which commonly have a peak workforce of around 100 workers.
Asian giant hornets pose threats as an invasive species in North America. These insects are efficient predators with complex hunting behaviors. While Asian giant hornets prey upon a wide range of insects, they are capable of attacking honey bees. Under the right conditions, Asian giant hornets can decimate hives of European honey bees (Apis mellifera) within a few hours. Their potent stings can also pose medical concerns for humans.
2) What’s the risk in the Midwest?
Based on the current situation, the risk from Asian giant hornets in Wisconsin and the Midwestern US is extremely low. To date, Asian giant hornets have never been found in Wisconsin or surrounding states. A very small number of Asian giant hornets were spotted in southwestern British Columbia and northwestern Washington state in the second half of 2019. For Wisconsin, these sightings have been roughly 1,500 miles from us. At the time this article was written (early May 2020), Asian giant hornets had not been spotted in North America in 2020. Update 5/27/20: we recently learned that AGHs have made it through the winter in North America. This species recently resurfaced, as reported in the New York Times. Despite this recent finding, all confirmed sightings of the AGH are from the Pacific Northwest and these insects pose little risk for the Midwest at this time. Update 12/20: No substantial changes by the end of 2020—in North America, AGHs are still only known from far northwestern Washington State and nearby parts of British Columbia. This insect has not been documented anywhere outside of that range.
3) What’s the timeline of the Asian giant hornet story?
Asian giant hornets have gotten a lot of attention in the news recently, but these stories really missed the main “action”, which occurred roughly half a year ago. (Imagine if Sport Illustrated took half a year to write about the Super Bowl’s winning team!). The story of the Asian giant hornet in North America began in August of 2019 when a beekeeper in Nanaimo, British Columbia (SE Vancouver Island) spotted these wasps. Three specimens were collected at the time and their identity was confirmed.
Also in August of 2019, a beekeeper in Northern Bellingham, Washington (US) observed Asian giant hornets, but no specimens were collected. Back in Nanaimo, British Columbia, an Asian giant hornet nest was located and eradicated in an urban park (Robin’s Park) in September. A month later (late October, 2019) a specimen was photographed in nearby mainland British Columbia (White Rock, BC). Around that time, the same beekeeper in Northern Bellingham, Washington observed Asian giant hornets attacking a hive. The last sighting of the Asian giant hornet occurred near Blaine, Washington in December of 2019, when a dead specimen was collected and a live specimen was spotted at a hummingbird feeder.
Update June, 2020: Small numbers of AGHs have been reported in North America—but only in the pacific Northwest.
4) Have Asian giant hornets become established in North America?
The ability of the Asian giant hornet to survive and spread in North America is not understood at this time. In its native range, the Asian giant hornet is associated with forested and low mountainous areas with temperate or subtropical climates. A key unanswered question at the moment is: have the Asian giant hornets successfully overwintered in North America? Update 5/27: we recently learned that AGHs have made it through the winter. This species recently resurfaced, as reported in the New York Times.
Asian giant hornets overwinter as queens. If previously fertilized, queens attempt to establish nests during the spring months. Established nests won’t produce the next batch of queens to carry on their “blood lines” until mid-fall, meaning that responders monitoring the situation in the Pacific northwest will have roughly half a year to hunt down any nests. For this reason, 2020 will be a critical “make or break” year in the story of the Asian giant hornet in North America.
Responders in the Pacific Northwest have plans to monitor for Asian giant hornets with traps and visual methods. If spotted, individual hornets can potentially be tracked back to their nest to allow responders to eradicate the colonies. Full details of the USDA response plan can be viewed here.
5) Health risks to humans are low
By referring to the Asian giant hornet as “murder hornets”, recent news stories have given the false impression that these insects pose a regular threat to humans. Many stories have repeated the claim that Asian giant hornets kill around 50 people a year in Japan, where these hornets naturally occur. In reality, the actual numbers are much lower. Based on publicly available data from the Japanese e-Stat statistics portal, from 2009-2018 an average of 18 deaths were reported annually in Japan from hornets, wasps, and bees combined. For comparative purposes, roughly twice as many annual deaths (average of 35) were reported as the result of slipping and drowning in bathtubs over that same period of time.
Nonetheless, Asian giant hornets do have potent venom and 1/4 inch-long stingers, which pack a punch. Due to their large physical size, a relatively large volume of venom can be injected leading to painful stings. If many stings occur (such as if one were to disrupt a nest), medical attention is advised.
6) Are there any look-alikes?
While we don’t have Asian giant hornets in Wisconsin or the Midwest, we have plenty of other insects that are currently being mistaken for the Asian giant hornet or could be mistaken for these hornets later this year. Panicked individuals thinking they’ve found an Asian giant hornet might end up killing native, beneficial insects which pose little risk to humans—such as bumble bee queens, which are currently trying to establish their nests for the year.
Historically, the UW Insect Diagnostic Lab receives many suspected reports of Asian giant hornets every year—all of these have been misidentifications by the submitters.To date, no confirmed sightings of the Asian giant hornet have occurred in Wisconsin or the Midwestern US. However, with the media spotlight on the Asian giant hornet, an increase in false reports is expected at the UW Insect Diagnostic Lab this year. Click the diagram below to view a
Some of the commonest look-alikes include:
Cicada Killer Wasps (Sphecius speciosus) These are the closest match in terms of size. However, these solitary ground-nesting wasps are really quite harmless, unless you happen to be a cicada... Because these insects don’t have a colony to defend, they are very unlikely to sting. This is the top look-alike reported to the UW Insect Diagnostic Lab every year. For additional details see this post: Asian Giant Hornets—Nope!
Great Golden Digger Wasps (Sphex ichneumoneus) These solitary ground nesting wasps capture and feed katydids and related insects to their young. Because these insects don’t have a colony to defend, they tend to be docile.
Pigeon Horntails (Tremex columba) These primitive wasp-like insects develop inside of decaying trees as larvae and can be common. They are not capable of stinging, but females do possess a prominent egg-laying structure (ovipositor).
Elm Sawflies (Cimbex americana) These plump, wasp-like insects cannot sting. The caterpillar-like larvae can feed on elms, willows, birches, and other hardwood trees.
Bumble Bees (Bombus spp.) The Midwest is home to over 20 species of bumble bees. These beneficial pollinators play important roles in the ecosystem. Bumble bees do live together as colonies and can act defensively if the nest is directly disturbed, but these important pollinators are generally docile. Annual colonies reach maximum size in late summer and naturally die out in the fall.
Yellowjackets (Vespula spp. & Dolichovespula spp.) The Midwest is home to more than 10 species of yellowjackets. Common species, such as the German yellowjacket (Vespula germanica) are typically around ½ inch in length. Yellowjackets are social insects and depending on the species, nests can occur in the ground, in hollow voids (such as soffit overhangs or wall voids), or as exposed as papier-mâché type aerial nests. Annual colonies reach maximum size in late summer and die out naturally in the fall.
Bald-Faced Hornets (Dolichovespula maculata) Our largest social wasp in the Midwestern US, reaching lengths of approximately ¾ inch. Bald-faced hornets are technically a type of “yellowjacket” but have a distinctive black and white appearance. These insects create large papier-mâché type nests, which can approach the size of a basketball. Annual colonies reach maximum size in late summer and die out in the fall.
Over 2,500 cases flowed through the doors of the UW Insect Diagnostic Lab last year, ranging from the typical June beetles through bizarre creatures that most humans will never see in their entire lives (like the itch-inducing pyemotes grain mite). Perhaps Forrest Gump said it best when he quipped, “life was like a box of chocolates—you never know what you’re gonna get.” A distinction amongst insects, however, is that the “box” contains 20,000+ possibilities in Wisconsin alone and over well 1,000,000 globally. With that said, a year at the UW Insect Diagnostic Lab is like having one humongous, box of really awesome chocolates, without all the calories.
With insects and related creatures, the weather can of course have a big impact and there definitely were examples of this in 2017. The current cold winter aside, the last two winters had been otherwise mild, giving a few insects suited for warmer conditions a chance to inch their way northward. Last spring and summer, this meant a bunch of sightings of an otherwise uncommon bee for our area known as the carpenter bee due to its habit of tunneling into unpainted cedar trim and other wood. In a typical year, I might see a few cases out of the southeastern corner of Wisconsin, but 2017 had regular reports of these bumble bee look-alikes during the spring and summer months. Similarly, praying mantids often meet their maker at the hands of a cold winter, but were surprisingly abundant in late summer and fall of last year. Ticks were also extremely abundant last spring and with the rainy start to the summer, mosquito numbers were at an all-time high in some traps. Mosquitoes were also a big deal in the news, with Wisconsin’s first confirmed reports of the Asian Tiger Mosquito last July.
The creature that amassed the most phone calls and emails in 2017 was the notorious Japanese beetle, which likely also benefited from the warmer than average winters these past few years. For Wisconsin gardeners and farmers, the Japanese beetle is certainly a formidable foe, but at least there are ways to mitigate the damage. In contrast, there’s another destructive pest wiggling its way into the spotlight in the state, which is much more difficult to control—an invasive earthworm commonly known as the jumping worm. While they may not be insects, these earthworms are creepy-crawly and can wreak havoc in gardens and flower beds, so I received a fair number of reports and questions. What stood out to me in last year was the rapidity with which these destructive worms have been moved around the state (moved—as in humans have moved soil, plants, mulch, and similar materials). Jumping worms were first found in the state in 2013 (in Madison), but have now been spotted in roughly half of the counties in Wisconsin. To make matters worse, we don’t have any highly effective tactics to prevent these worms from turning rich garden soil into the consistency of dry, crusted coffee grounds—gardeners beware!
In other insect news, it seemed to be a good year for monarch butterflies in 2017, and the rusty-patched bumble bee finally made it onto the federal endangered species list. I was pleasantly surprised by a number of confirmed sightings of the rusty-patched bumble bee in the state as well. Perhaps my favorite “bug” story for the year involved black widow spiders. It’s not common knowledge, but we do technically have a native black widow species in the state (Northern Black Widow, Latrodectus variolus). It’s a reclusive species and is rarely encountered in Wisconsin, but reports trickled in once or twice a week at some points during the summer months (details to follow in a future blog post).
With so many cases last year, we’re really only touching the tips of the antennae. If you’re interested in hearing more of the unusual stories from the UW Insect Diagnostic Lab, I’ll be giving a “highlight” talk on May 4th on the UW campus.
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!
What were Wisconsin’s top insect trends of 2015? In this post, we’ll look at the first half of our count-down.
This is the second post in a three part series. The first post of the series (2015’s diagnostic lab statistics) can be found here.
10) Mosquitoes and ticks:
Like most years, Wisconsin had a pretty good mosquito season. Overall, we were close to the average rainfall mark during much of the year, which meant the typical batch of mosquitoes starting after Memorial Day. In many parts of the state, mosquitoes were prevalent throughout June, July, and August. However, this is Wisconsin after all, and mosquitoes seem to be one pillar of summer culture along with beer, cookouts, and fishing. The silver lining of the mosquito story is the fact that West Nile Cases were low for the year, with only four confirmed human cases reported in the state in 2015.
While there wasn’t anything out of the ordinary with the mosquitoes last year, ticks seemed to have a particularly good year in the state. Deer ticks, which can vector Lyme disease can be found essentially statewide. From the standpoint of an emerging health threat, deer tick populations have exploded in the past few decades (our first deer tick wasn’t found in the state until the 1960’s). A recent nation-wide study found that deer ticks were found in nearly half of the counties in the U.S. One of the more alarming trends is urban encroachment. Historically, ticks seemed to be the type of creature you’d pick up if you were out hunting or hiking through the woods. In the recent past, we’ve noticed an increase of ticks found in more urban environments, such as parks and backyards. With roughly 40% of the adult ticks in Wisconsin carrying the microorganism responsible for Lyme Disease, this is an issue that will continue to exist in the state for years to come.
9) “Sucking Insects”
A certain group of insects (the Order Hemiptera) are sometimes known as the “sucking insects” because they possess tube-like mouthparts which are used by many species use to drink fluids from plants. Two of the members of this group, the aphids and the scale insects had a great year in 2015. When these insects feed on plants, a common sign is the presence of sticky, sugary honeydew, which attracts ants and yellowjackets, and can result in the growth of black sooty mold. Aphids and scale insects are common and typically present in low numbers, but the conditions must have been just right for their populations to thrive in 2015. As a result, there were many reports throughout the state of honeydew “raining” down from trees and shrubs onto vehicles, decks, outdoor furniture, and people below. If you felt “rain” on a sunny day last summer, the actual cause may have been honeydew dripping down from aphids or scales in the trees above!
8) Long Lost Pests: Japanese Beetle and Gypsy Moth
Two of our best-known landscape pests, the Japanese Beetle and the Gypsy Moth had been very quiet in 2014, but resurfaced last year. Japanese beetles had been low across the state in 2014, likely due to the brutal winter of 2013-14 killing many of the soil-dwelling grubs. While we did see an increase in beetle activity in 2015 compared to 2014, their numbers still seemed low compared to the long term average. However, with a milder el Niño winter, it’s possible that we could see increased winter survival and higher Japanese beetle populations in 2016.
Gypsy Moth populations have been low the past few years in Wisconsin. Damp spring conditions can result in a fungal disease killing many of the caterpillars, which likely helped lessen populations in the recent past. It’s also not unusual for some long-term cyclic patterns to be involved with insect populations. For a number of potential reasons, Gypsy Moth populations seemed to rebound a bit in 2015, and many reports of sightings and damage came in to the diagnostic lab, particularly from the south central portion of the state (Dane, Rock, Walworth Counties). Because Gypsy Moth can be a destructive defoliator of hardwood trees, it’ll be good to keep an eye out for this one in 2016 to see if the populations continue to climb.
7) Emerald Ash Borer
This is our most destructive forest pest in the state, and unfortunately, there doesn’t seem to be anything capable of completely stopping this pest. While we didn’t see many additional counties added to the quarantine map in 2015, there were many municipalities that detected EAB for the first time. At the moment, 39 of the 72 Wisconsin counties are quarantined for EAB and this number will continue to increase over time. Like Dutch Elm Disease in the past, Emerald Ash Borer is changing and will continue to change the appearance of our urban forests and woodlands for years to come.
6) Spotted Wing Drosophila
This invasive pest first showed up in the state in 2010, and became a significant fruit pest almost immediately. Since its introduction, SWD has spread widely and can be found in most counties in Wisconsin. Very similar to 2014, SWD was detected in dozens of counties across the state. SWD can attack a wide variety of fruit, but due to the fact that this insect doesn’t seem to become active until July, the late-season raspberry and blackberry crops are hit the hardest. Luckily Wisconsin’s famous cranberry crop does not seem to be favored by this invasive pest.
It happens every year in August and September: someone takes their lawnmower over a nest in the ground and really “stirs up the hornet’s nest”. Shortly thereafter, I get a call regarding these black and yellow stinging “ground bees”. Technically, these nests are neither the work of hornets nor bees, but rather yellowjackets. [There are actually ground-nesting bees, although they tend to be docile, solitary creatures; see this post from April].
Yellowjackets are a type of wasp, related to paper wasps and bald-faced hornets—all of which can be abundant this time of the year. In fact, wasps are one of the most common insects reported to the diagnostic lab in late summer each year. Depending on the species, yellowjackets (Vespula species) can nest in pre-existing cavities in the ground, above ground, or in hollow voids (such as wall voids and soffit areas of roofs). Bald-faced hornets (Dolichovespula maculata) are the larger cousins of our common yellowjackets, and can produce basketball-sized papier-mâché style nests that can often go unnoticed until the leaves fall off the trees in fall. Paper wasps (Polistes species) are more slender in appearance than yellowjackets and build the open, umbrella-like nests that often hang from soffit areas.
Yellowjackets, bald-faced hornets, and paper wasps are what we refer to as social wasps, meaning that they live and work together as a colony. Each species varies in its particular traits (body size and coloration, nest location, colony size, etc.) and we have dozens of species in our area. An interesting point about the biology of social wasps is that a queen starts her colony from scratch each spring and the colonies die out in the fall. A small group of females designated to become queens the following year does make it through the winter in sheltered locations such as rotting logs. The tiny colonies from spring build up in size throughout the summer, reaching their maximum size this time of the year. This can give the impression that the insects appeared abruptly, when in reality, the colonies have been there and the wasp populations have built up rapidly over the past few weeks.
Because the colonies die out in the fall, if a wasp nest is located in an infrequently visited back corner of your yard, simply waiting for a few hard frosts will ensure that the colony has met its demise. If a colony is located in a spot where you’ll likely have run-ins, there are some reliable ways to eliminate them, but choosing the correct tool for the job can be critical!
It’s summer and large wasp zips past. A quick Google search has you convinced you’ve discovered an Asian Giant Hornet (aka “murder hornet”). . .except they don’t occur in our area. What’s you’ve likely encountered is a common, native insect known as the “cicada killer“. They can be surprisingly in Wisconsin and much of the Midwest and are surprisingly docile—unless you happen to be a cicada, but I’ll get to that later...
The things entomologists do for the sake of their curiosity:
This past Wednesday I found myself thinking about Hollywood Horror Films while crouched along a hot sunny rock wall on the UW-Madison campus patiently waiting for one of our largest wasps to land mere inches from my face. What gives?Cicada Killers: One part cold-blooded killer, one part flying teddy bear (check out how fuzzy that thorax is!).
Part of their basic biology plays out like a B-Class horror movie: a victim (cicada) is injected with an incapacitating chemical before being dragged to an underground lair and left to be eaten alive. While it sounds bizarre, this is actually fairly common in the insect world and there are many examples of wasps that paralyze their prey and haul them off to their nests in the ground to feed to their young. (One of my favorites is the Zombie-making “emerald cockroach wasp“)
Sometimes pushing two inches in length, cicada killer wasps (Sphecius speciousus) are amongst our largest wasps in the Midwest and resemble large yellowjackets. They specialize in tracking down and attacking cicadas, which the females haul back to the nests they had previously dug in patches of bare soil. Despite their “killer” habits, these insects are usually quite docile and non-aggressive towards humans. Unlike their smaller yellowjacket cousins which have a large colony to defend, cicada killers are solitary nesters. You can actually get within inches of them without provocation, although the territorial males may fly around to check you out.
Cicada killers can be common in the state and also happen to be common on the UW-Madison campus. You can often find them near some of the dorms along the Lakeshore bike path and also in the rock wall along the Linden Drive pull-off near the Nutritional Sciences Building (just in case you’re in the mood to meet them up-close and personal.) . They’re also common many other places in Wisconsin and the eastern US in areas with sandy soil.
In the mood for an actual horror movie involving giant predatory wasps? The recently released “Stung” might be perfect for you. . .
If you’re looking for additional information on Asian giant hornets and their look-alikes in our area, check out this post.
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!