Category Archives: Wasps and Bees

Under the Microscope: Arthropod Trends of 2017

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.

Finding a pyemotes itch mite is like trying to find a needle in a haystack, except in this case these microscopic mites were in a farmer’s batch of corn. Photo credit: PJ Liesch, UW Insect Diagnostic Lab

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.

Asian Tiger Mosquito (Aedes albopictus). Photo credit: James Gathany, Centers for Disease Control

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!

Speaking of invasive species, the emerald ash borer has continued its march through the state and now has footholds in some of our northern counties including Chippewa, Douglas, Eau Claire, Marathon, Marinette, Oneida, and Sawyer counties.  Unfortunately, our greatest concentrations of ash trees are in the northern part of the state (e.g. black ash in swampy areas), and the loss of ash from northern wetland areas could result in significant ecosystem effects.  Other recent invaders like the spotted wing drosophila and the brown marmorated stink bug had busy years as well.

Rusty patched bumble bee (Bombus affinis) visiting a flower in Middleton, WI. Photo credit: Rick Terrien

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.

 

 

 

The Case of the Hitchhiking Bog Wasps

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.

Bog Wasp-Pseudochalcura gibbosa
The tiny, hump-backed wasp: Pseudochalcura gibbosa. Photo Credit: PJ Liesch, UW-Entomology.

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!

Wisconsin’s Top Insect Trends of 2015 (#10 – #6)

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.

Deer Tick
Adult female deer tick. These ticks can now be found throughout the state and roughly 40% of adults are carrying the microorganism responsible for Lyme Disease. Photo credit: Scott Bauer, USDA Agricultural Research Service, Bugwood.org

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!

Lecanium Scale
Lecanium scales producing sticky honeydew (clear droplets).  Photo credit: Ronald S. Kelley, Vermont Department of Forests, Parks and Recreation, Bugwood.org

 

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.

Japanese Beetle
The infamous Japanese Beetle. Photo credit: David Cappaert, Michigan State University, Bugwood.org

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.

Up Next, Part III:  Wisconsin’s Top Insect Trends of 2015 (Numbers 5-1) 

Yellowjacket Season

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].

Ground nesting Yellowjackets
Ground-nesting yellowjacket workers at the entrance of their nest. Photo Credit: Jeff Hahn, University of Minnesota

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.

Bald Faced Hornet Nest
Aerial, papier-mâché style nest of the bald-faced hornet.  If you click to see the enlarged version, you’ll notice the head of a lone worker peering out from the entrance of the nest. Photo Credit: Pat Malone, Trempealeau County UW-Extension

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.

Paper Wasp Nest
Paper wasps on their open, “umbrella” style nest. Photo Credit: Jeff Hahn, University of Minnesota

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!

To learn more about the biology of social wasps as well as how to manage wasp nests, check out this webpage: http://www.extension.umn.edu/garden/insects/find/wasp-and-bee-control/

 

The “Killers” on Campus

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!).

Cicada Killer 2_opt
Cicada killer wasp (Sphecius speciousus) on the UW-Madison campus. Photo credit: PJ Liesch, UW-Entomology

Part of their basic biology plays out like a B-Class horror movie: a victim 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“)

At nearly two inches long, cicada killer wasps (Sphecius speciousus) are amongst our largest wasps in Wisconsin 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 Killer
Territorial male cicada killer wasp trying to stare me down for getting too close to his rock. Photo credit: PJ Liesch, UW-Entomology [Click for a larger image]
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.)

In the mood for an actual horror movie involving giant predatory wasps? The recently released “Stung” might be perfect for you. . .

Tobacco Hornworm et al.

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!

Hornworm
Tobacco hornworm caterpillar with dozen of cocoons from parasitic wasps. Photo courtesy of Deb Zaring.

It’s a fly, it’s a wasp, it’s a bee?. . .

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.

Anthidium manicatum, the "European wool carder bee"
Anthidium manicatum, the “European wool-carder bee”. Photo credit: PJ Liesch