Does a mild winter mean more insects?
With increasing frequency, as spring rolls in, ROM entomologists are asked this question: will mild winter temperatures result in more bugs this spring and summer? Unfortunately, there is no simple “yes” or “no” answer to this question — the best response is “It depends”.
There are many variables affecting insect population size: humidity/moisture, habitat suitability and food resources, just to name a few. What may be good for one species is not necessarily good for another. Furthermore, natural variation in population size occurs from year to year in most species.
Early emergences, yes! After a mild winter, some insects emerge or becoming active earlier than normal; but seeing insects in March doesn’t necessarily mean that we will be seeing more of them later in the season. Most insects have a limited life span so if they emerge earlier, their flight season will end earlier.
Black flies. According to ROM Entomology curator Dr. Doug Currie, the first black flies come out when trees first begin to bud. Winter temperatures have little impact on black fly numbers as most species overwinter as eggs in stream beds. But if ice break-up occurs earlier than normal, then the season is also likely to begin sooner. Day length also serves as an important cue for emergence of early-season black flies. In terms of numbers of black flies, the reduced snowpack and lack of rain means that fewer eggs are likely to survive. So what does this all this mean? If there is warm, dry, weather in the spring, there will be an earlier than normal emergence of black flies. On the other hand, there will be fewer adults on the wing (flying), and it’s likely that pest species will disappear well before cottagers begin their late spring or early summer vacations.
Mosquitoes. Certain species overwinter as adults, which hibernate in protected spaces. These are the ones that come out earliest in the spring. However, most Ontario species lay winter-hardy eggs that hatch when conditions are right – typically after snowmelt. Given that mosquitoes breed in variously-sized pools of standing water, a lack of snow means that conditions are less-than ideal for these later emerging populations. Of course, all of this can change should we experience a period of extended heavy rainfall. And there’s one more caveat – mosquitoes are on the wing from early spring till late fall; and many species have multiple generations per year. The upshot is that early spring weather only affects the overwintering stages of mosquitoes (and perhaps the first generation or so). Making predictions based only on winter weather is not useful if spring conditions are wet.
Butterflies. Require flowers to nectar and food plants for their larvae. If they start flying earlier than usual, will there be food for them? The same can happen with queen bees that emerge too early from hibernation, will there be nectar sources?
A possible increase in pests could be balanced by an increase in ‘good’ bugs. Perhaps more wasp (many social wasps are insect predators so they are beneficial) and bee queens survived the winter. If more of a pest species survived, maybe more of their predators survived as well. It is amazing how nature balances out!
Ticks. The blacklegged deer ticks that carry Lyme disease are found in many places in Ontario. They have a greater survival rate with enhanced moisture conditions in late spring.
The early emergences of some species could end up having a negative impact if we suddenly have a cold snap and many of them are killed. It is possible that the newly emerged insect stage isn’t as tolerant to cold temperature as the overwintering stage. Then there would actually be fewer of that species of insect.
A mild winter has no impact on indoor arthropods since temperature is pretty constant indoors year-round.
So early emergence doesn’t necessarily mean more insects; there may, in fact, be fewer numbers of certain kinds of insects. On the other hand, insects that are adapted to warmer and drier conditions, like grasshoppers, may thrive in those situations. How things play out depends largely on weather in the spring months. If you REALLY want to know what the bugs will be like after a mild winter, your best bet is to consult a climatologist!
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Mild winter weather will get bugs buzzing sooner, CBCNews