Tag Archives: Phenology

In Defense of Ground Bees

“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

Entrance of a ground-nesting yellowjacket nest in late summer. These might be black and yellow, but they aren’t bees… Photo credit: Jeff Hahn, U. Minnesota.

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.  

A solitary ground nesting bee guarding the entrance to its nest in a city park in Middleton, WI. Photo credit: PJ Liesch, UW Entomology.

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.

Post-jog entomologist next to five solitary bee nests. These bees are extremely gentle and unlikely to sting. This portion of a local park had thousands of solitary bees flying around. Photo credit: PJ Liesch, UW Entomology.

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 of  adult 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. 

If you’d like to learn more about Wisconsin’s bees, check on the Wisconsin Bee Identification Guide or the US Forest Service’s Bee Basics: An Introduction to Our Native Bees. If you have solitary ground-nesting bees in your yard and would like to teach others about these amazing pollinators,  click the image below to get a  sign to laminate and post:

A yard sign about wild bees

Snow Fleas: When a “Flea” isn’t a Flea

Fleas (Order Siphonaptera) can be an unwanted surprise—no one wants fleas on their pets or in their house.  Our commonest flea on both cats and dogs in the Midwest is the “cat flea” (Ctenocephalides felis), and this same species can also live on a wide range of wild animals.  Cat fleas may be annoying but can be controlled with a diligent multi-pronged approach: chatting with your veterinarian to pick a proper treatment for your pet and regular and thorough vacuuming. In heavy infestations, carpets and furniture may also need to be treated.  While fleas could be encountered anytime of the year, I see the vast majority of flea cases at the UW Insect Diagnostic Lab in late spring and summer.  In contrast, cases of fleas are few and far between during the winter months due to the dry conditions and lower temperatures which can be hard on these insects.

There is one type of “flea”, however, that I see regularly through the winter months—the “snow flea”.  Snow fleas (Hypogastrura nivicola   and close relatives) aren’t actual fleas and rather than a pest, these harmless creatures are a beneficial curiosity.  Their cold tolerance and ability to launch themselves into the air account for their nickname.

Up-Close View of a Snow Flea. Photo Credit: Daniel Tompkins via Wikipedia

The snow fleas we’re talking about technically aren’t even insects and belong to a closely related group of arthropods known as springtails (Collembola).  Springtails get their name from the furcula—an anatomical structure on the underside of their bodies, which springs downwards to catapult them up into the air.  Springtails can’t “jump” very far by human standards given their tiny size (less than a tenth of an inch long), yet they can easily launch themselves many times their own body length in a mere blink of an eye (video).

The snow flea is unusual for springtails (and most arthropods) in the fact that these creatures can remain quite active during the winter months.  As discussed in this post from last March, insects and other arthropods have a variety of strategies to make it through winter, ranging from migration to freezing solid in some cases.  The vast majority of arthropods are inactive during winter, but some, like the snow flea, seem perfectly content wandering out on the snow.  With their tiny size and dark grayish bodies, snow fleas can almost look as if someone had dumped out a pepper shaker on the snow.

Snow fleas in their element. Photo Credit: Christa R. via flickr.

Their ability to remain active at frigid temperatures is due to the concentration of specific proteins in their bodies, which serve as a cryoprotectant or natural “antifreeze”.  During the rest of the year, these creatures simply blend in amongst fallen leaves where they scavenge upon decaying materials and help with nutrient recycling.

These creatures are truly a winter curiosity if you haven’t encountered them before.  The next time you’re out snowshoeing or cross-country skiing, keep an eye out for these tiny acrobats on the snow.


Final Note: Overseas, our friends in the UK have different creatures they refer to as snowfleas—insects from the genus Boreus, which we’d call “snow scorpionflies” in our area.