Yesterday afternoon the sun warmed up my south-facing porch and the latest “sign of spring” emerged. Dozens of dark spotted, orange “ladybugs” crawled out from under the siding and warmed themselves in the welcome sunshine. These “ladybugs” (who are neither all female nor “bugs”) are more appropriately called “ladybird beetles.” They are widely recognized as effective bio-control agents against aphids and scale insects and are one of the relatively few types of insects that overwinter as adults. Back in the late days of autumn these beetles found their ways into the tiny, protected spaces under the porch siding (and inside the garage and inside the house and under the loose bark of trees, etc.) and have been sleeping away the winter.
Most insects overwinter as cold resistant, relatively inactive eggs or pupae, but there are some distinct advantages along with some potentially fatal disadvantages to adult hibernation. The big advantage is that the spring emerging adult is all set to immediately respond to a warming trend and then go and disperse, gather food resources, and mate (eggs and pupae have a lot of growing to do before they are ready to go out and similarly “seize their days”). The overwintering adults, then, have first access to the abundant resources of the awakening spring world. Potential disadvantages include the hibernating adult life stage’s vulnerability to both predation (all winter many birds like the chickadee constantly work their beaks into any tiny space looking for hibernating insects) and metabolic exhaustion while they are in their hibernaculae (stored body energy must be used to keep the large, complex adult form alive even in its quiescent state). Further, the adult may emerge too early in the season and get fatally caught out in the open in the sudden return of winter conditions.
So it’s a balance between the competition for being first and the safety of waiting until a seasonal “all clear” has been sounded. The ladybird beetles have evolved the strategy of being first.
Other insects that overwinter as adults include bumblebees, mourning cloak butterflies, leaf footed bugs, and stink bugs. On warm days in March the mourning cloaks will start flying through the upper tree branches along the nature trail and large, low flying bumblebees will buzz their way through the leafless vegetation. And, regularly through the winter on sunny days or during times of overwrought furnace activity, hibernating leaf footed bugs and stink bugs wake up enough to walk across my desk or stumble through the labs and classrooms and hallways up here on campus.
Ladybird beetles, by the way, were the subject of a USA Today article just last week (January 27, 2012). New York had long ago designated the native, nine-spotted ladybird beetle as their official state insect. In recent decades, though, this particular ladybird species’ numbers had declined, and it was even feared to be extinct in New York State. Entomologists at Cornell, though, found a population of nine-spotted ladybird beetles on a farm on Long Island and are now actively breeding them in their laboratory. They hope to figure out exactly why the nine-spotted ladybird has so greatly decreased in numbers. They speculate that competition from introduced, exotic ladybird species (like the seven-spotted from Europe and the harlequin from Asia (which, I believe is the ladybird living out on my porch!)) may have been the cause or, possibly, the nine-spotted has interbred with these introduced species and has thus become unrecognizable as a species.
By evening, the ladybird beetles on my porch had returned to their hideouts under the siding. I hope that they didn’t pay too much of an energetic price for the hour or two of activity and will be able to wait out the next few months until there is a genuine spring upon us.