Left: Polistes dominula and Right:Vespula germanica wasps that emerged on December 20, 2014 and January 25, 2015, respectively. Janet Scott, Medicine Hat, Alberta.
The winter weather in Regina this year has fluctuated quite a lot…you might even say that some days have been Saskatchewarm! For us humans, these warm periods can be a welcome break to the icy-cold conditions of the prairie winter, but for some bees and wasps (and many other insects) it can be a death sentence. For most insects in Canada, winter is the time for hibernation, and they do this using a combination of “cool” chemistry, appropriate hibernation site choice, and just plain luck. The chemical strategy used by most insects involves producing anti-freeze compounds within their “blood” to keep from freezing; less commonly, some species use chemicals to promote freezing in a fashion that does not destroy their cells. We call these two groups freeze “intolerant” or “tolerant” strategies, respectively. Bees and wasps, and most insects in fact, use the former strategy and the winter is best spent in sheltered locations (hibernacula) that are buffered against extreme cold temperatures to prevent freezing.
Most bees and wasps in Canada spend the winter in the nests in which they developed from eggs and do not typically emerge until the spring or early summer, depending on the species. These are almost all solitary species (i.e., all females lay eggs, with no workers). Our native social species, including bumble bees and social wasps, typically winter as mated queens, having emerged in the fall, fed on nectar, mated, and then found hibernation sites in the soil, under tree roots, in compost piles, etc. Under a deep snow cover, conditions in these locations can be comfortably cool and consistent, the latter being very important. Some individuals, however, may choose sites that are only partially sheltered from winter conditions, but perhaps not sufficiently protected from extreme fluctuations in temperature (i.e., highs and lows), as have been seen recently in the prairies. During periods of exceptionally warm winter weather, it is not that uncommon to see some insects become active, including these queen bumble bees and wasps (Figure 1; images provided by Janet Scott, Medicine Hat, Alberta). Luckily, in some parts of the world, insects can find some “winter-flowering” plants to feed on, though this is hardly ever the case in Canada (at least east of the Rocky Mountains). So what is the fate of these winter-emerging bees and wasps in Canada? For most of them, it is probably death as it seems unlikely that they would find food plants for energy, and even more unlikely that they will be able to get back into suitable wintering sites. For bumble bee queens and social wasps, these losses mean the potential reduction of new colonies in the spring.
So what can be done to help them? Well, in late winter or early spring, these insects could use a lot of energy being active for a few warm hours/days without replacing food reserves in their bodies, and the scarcity of flowers at this time in most of Canada does not help. A sugar solution is the solution…they can be helped by providing a sugar mixture (50/50 sugar and warm water) in a small container (i.e., a drink lid), placed near the insects head. Shortly, their tongue will be visible and they will use the energy they obtain to heat their bodies up and possibly fly off. Perhaps they can find a new sheltered site to spend the rest of the winter in, and will survive. This is what is most often recommended to help early emerging bumble bees, though one never really is certain of their fate. A second solution, especially in the middle of the winter when we know extended periods of cold are coming, is to keep them indoors. This is typically not recommended as a long term solution, though there are hibernation studies suggesting that it is possible, and even successful. Again the key is cold and consistent temperatures, such as in a fridge or cold cellar. Fridges are usually too dry to be adequate, so artificial humidity will have to be provided. A semi-airtight container provided with a damp sponge (i.e., moist, not dripping) should work (Figure 2), though the insects must not come into contact with the source of moisture as it will promote mould growth (it should be replaced periodically). Having the insects in separate, breathable containers within the large container is ideal. Once the early spring weather returns, these bees can be warmed up slowly (outside in a sheltered area), and if they become active, then they can be released, hopefully coinciding with early spring flowers such as dandelions.
A possible solution to wintering “early-emerged” bees and wasps in a fridge.