Originally published in the FSS newsletter, October 2022.
Insect survival strategies
Insects are adapted to survive varying climates, wide shifts in temperature, and periods of adverse environmental conditions. Insects use both behavioral and physiological adaptations to combat freezing temperatures and increase their chances of overwinter survival. Many insects maintain a low level of activity during winter months while others enter diapause, a type of dormancy. Freeze-susceptible or freeze-avoidant insects produce many antifreeze compounds to reduce the lethal freezing temperature of their bodies, such as alcohols, sugars, and ethylene glycol (the same compound found in car antifreeze). They exhibit behavioral shifts and seek out dry, protected overwintering areas such as behind tree bark, burrowing into the ground and inside refuse piles. Freeze-tolerant insects do not freeze entirely, but instead internal fluids freeze, which draws moisture out of living cells to reduce their lethal freezing temperature.
Insects are predominantly freeze-avoidant in cool to mildly cold areas and freeze-tolerant in cold areas. Insects aid in winter survival through partial dehydration and reduced feeding, which reduces the chances that excess water within their cells or guts will freeze. Some insects survive winter at a specific stage of growth that is more protected from the elements, such as eggs in a protective egg sac or pupae encased in a hard cocoon, which do not require food or water. Insects overwinter and go into diapause because the resources they need are not available in the winter.
Why they end up in your building
Many of the more common insects that overwinter in structures do so in the adult form. When we approach the autumn equinox, the light-dark cycle or photoperiod begins to change their behavior. Reproduction ceases, feeding reduces or stops altogether, and they begin exhibiting what is termed diapause-seeking behavior even if it is still very warm outside. This just means they begin looking for a place to spend the cold months. Unfortunately, many of our businesses, factories, homes, garages and offices have the perfect microenvironments that they seek: cool but not cold, dark, low humidity, no wind. Once inside, they can be problematic all winter long. If they are too warm, they will remain active and fly toward lights. Insect light traps can therefore be very effective if properly placed on the interior of the structure. Residual pesticide applications can help reduce the number of insects that gain entry. However, the best opportunity for this type of treatment is from the last two weeks of September to the first two weeks of October.
Boxelder bugs
During the fall, boxelder bugs become a major nuisance as they congregate and enter homes by the thousands. Boxelder bugs primarily crawl into structures from ground level but also fly to higher elevations. Their primary route of entry includes gaps in soffits and chimneys, electrical wiring cutouts, garage doors, poorly sealed windows, and especially underneath siding and trim pieces. They will congregate in warm places in a home. Although boxelder bugs enter a state of diapause, they can quickly become active even in the dead of winter on mildly warm days.
Asian lady beetles
Asian lady beetles are native to eastern Asia and considered an invasive species in the US that is an increasing threat to native species. They produce an unpleasant odor when frightened or crushed and tend to stain surfaces. They have also been known to bite humans. Asian lady beetles enter homes in fall months by the thousands through every imaginable crack, crevice, and opening, and gather in warm places once inside.
Stink bugs
Stink bugs are pests of fruits and vegetables, which use their piercing-sucking mouthparts to damage crops. Stink bugs such as the brown marmorated stink bug are highly attracted to light. External and interior lights should be reduced during times of heavy stink bug movement. They start the search for overwintering sites in late summer and can become a severe nuisance inside structures. They will congregate in warm places once inside. Stink bugs are difficult to control due to their size and large numbers.
Cluster flies
Cluster flies are strictly parasites of earthworms and do not present any known human health hazards. These slow-moving flies become pests as they hatch in late summer and early fall. Cluster flies may be present in large numbers and are difficult to eradicate once inside the structure. These flies are often located in areas that are difficult to access for treatment, such as attics, wall and roof cavities, window frames and soffits. Cluster flies are especially prevalent in homes with multiple stories, attic spaces with windows, and gaps around windows, doors, and chimneys.
Again, once inside, properly placed insect light traps are often your best control option.