One of the coldest experiences that I have had was when I went camping in the woods with my friends this year. It was one horrible, cold night and none of us knew how to build a fire. We all slept in our sleeping bags, miserable because of the freezing temperatures. Once we woke up in the morning, none of us could feel or even move our toes and feet. Needless to say, it was one cold experience. Insects have to face these challenges every year in the winter. This winter especially is the coldest one I have lived through. Imagine having to be outside surviving in this climate each and every day. That is a significantly difficult trail to overcome. Insects use many adaptations and various tactics to overcome the winter such as: supercooling, hibernations, and migrations. One amazing example of an insect overwintering tactic is displayed by the goldenrod fly. As I was reading chapter 14 in Heinrich's informative novel, I quickly learned new tactics to overwinter, and this one tactic amazed me because I have never seen or heard anything quite like it before. The mature goldenrod fly lays its egg within a growing plant stem, and the new found larva secretes some chemical to induce growth, a gall, around the area the egg was injected. The tumor now becomes the new home for the larva and is in a prime location for the larva to extract any nutrients from the plant so it may survive. During the larva phase, it also chews a tunnel to the exterior of the gall using its mandibles. Then the larva goes back into the gall for hibernation until it pupates and emerges as an adult fly, who then will emerge from the gall to enter its reproductive period.
Above is the gall of a goldenrod fly larva who has recently emerged, or has been eaten due to the size of the extraction site. The image below the gall is of an adult reproductive goldenrod fly.
http://www.pbase.com/laroseforest/galls (link where picture was obtained; no author)
In addition to the golden rod flies, one other specimen was quite fascinating. Heinrich describes the banded woolly bear caterpillar as an awe inspiring creature. These larvae actually live throughout the winter, not by hibernating, but by internally adjusting their chemical composition. So the caterpillars won't freeze and die, these specimen change their chemical intercellular composition. They change their lattice formation of water so it all won't freeze and expand within their cells causing non programmed apoptosis, thus resulting in cellular destruction. These specimen chemically manipulated their internal structure within their cell not only to osmotically remove water, but also to add glycerol, which acts as a form of antifreeze. These two examples that Heinrich described fascinated me, and I decided if I was an insect I would want to choose to be the banded woolly bear caterpillar because of its unique properties of adjusting its chemical composition. After reading these different tactics and examples, a new appreciation for insects developed out of me. They are very successful creatures who can manage to do extraordinary and seemingly impossible tasks like surviving in these harsh winter conditions. Insects can live outside through the winter; how many humans can say that they can do the same? None, that is why insects are incredible specimens because they are capable of anything due to their evolutionary adaptations.
Above is the image of a woolly banded bear caterpillar.
Image provided by Wikipedia
http://en.wikipedia.org/wiki/File:IC_Pyrrharctia_isabella_caterpillar.JPG
Great post (and images)!
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