Northern Minnesota phenology report: November 2009
By John Latimer, KAXE Radio, Grand Rapids
The last of the meadowhawk dragonflies will put in an appearance in early November. These small, bright red, insects are among the last to fly about in the fall. A warm day or two in the early part of the month will send them out in a last and probably fruitless search for other flying insects.
Flickr photo “Ruby Meadowhawk” by Jim Frazier. Original.
If you have been observing them throughout the fall you may have noticed them flying in tandem with the female periodically touching her abdomen to the grass. She is depositing eggs. Her strategy is to place her eggs on stalks of grass that will be inundated in the spring. Once awash the eggs will begin to develop and the larval stages will terrorize the shallow ponds and lake edges until late summer when they will emerge and terrorize the flying insects.
Those eggs mistakenly laid in the grass that may be your lawn will likely never develop. No one is perfect and least of all the meadowhawk dragonflies, but what they lack in foresight about those areas likely to flood they make up for in sheer numbers of eggs laid. Some of them will end up underwater and the species will survive.
Flickr photo “Dragonfly” by Chris Coomber. Original.
In the case of the meadowhawk dragonflies they survive the winter as eggs or larvae, but what about the Compton’s tortoiseshell or Mourning cloak butterflies? How do they survive the cold? They over-winter as adults and without an approach to overcome the cold they would freeze and die. For many insects the strategy is freeze avoidance.
There are three elements to freeze avoidance. First, the insect produces an anti-freeze which circulates in the blood. These special proteins bind with any ice crystals that may form keeping them small and preventing them from doing damage.
Second, they produce sugars and sugar based alcohols which act to lower the freezing point of any water in the body. These typically take the form of glycerols that by mid-winter may constitute 20 to 25% of the insect’s total body weight.
Flickr photo “Chionea species” by C Wood. Original.
The final part of a freeze avoidance strategy involves finding a dry location. Staying away from water and the resulting ice is imperative. Ice can act as a nucleator for the development of further ice crystals. The butterflies must find secure dry locations, other insects might construct waterproof cocoons or some other personal protection, but the butterflies lack this ability. This perhaps explains why I find so many of them in my garage.
John Latimer is well known throughout northern Minnesota for his phenology work. He appears weekly on KAXE radio in Grand Rapids, and audio and twitter archives are available here. His work is a frequent feature on MyMinnesotaWoods. This article also appeared in the Duluth Senior Reporter. It is printed with the author’s permission.