Wednesday, July 22, 2015

Dazzling Insects of Summer‏

Caterpillar white dotted prominent Nadata
Too often we focus in our nature studies on one particular group of animals or plants (birds or mushrooms for example). I am not sure what the origin of this "species-chauvinism" is, but it denies the naturalist in all of us some remarkable opportunities to marvel at the wide biodiversity of life all around us. Insects are abundant both in numbers and species in any location, although they are primarily found during warm periods.  Look around you and begin to appreciate the remarkable variation in insect form and color.  A basic guidebook is invaluable in beginning to put names on common species: Kaufman's "Field Guide to Insects of North America" is a great place to start.

Some of my favorite insects are the odonates, the damselflies and dragonflies. They can be a challenge to identify but the males are often very colorful and distinctive.  The male azure bluet damselfly is a tiny jewel that is most often seen near ponds that lack fish, which would prey on its aquatic larvae.  

Amber-winged spreadwings in "wheel" position
Similarly the amber-winged spreadwing damselfly is found in greatest numbers at fish-less ponds.
Amber-winged spreadwings ovipositing
There are large numbers at a pond I built in the woods without fish; in mid-July they are mating (in the "wheel position") and laying eggs (male and female in tandem) in plant stems.  The mating scenario is bizarre- the male transfers sperm to its second abdominal segment, catches a female and holds her by the neck; she bends her abdomen forward and receives the sperm from the accessory genitalia. 

Odonates may be primitive but they have a complex breeding behavior. Their feeding behavior is primal predation and they eat almost anything that flies. The "T rex" of dragonflies is the huge dragonhunter, a predator that eats other dragonflies.  It is found along rivers and streams and spends a great deal of time flying around its territory.  
Dragonhunter on Beaverdam Trail

The beetles are the largest group of any kind of animals and thus can be a nightmare to identify.  The English scientist Haldane has been quoted as saying that the creator if he exists has an inordinate fondness for beetles!  Yet despite this bewildering array of beetles, one can easily learn the ten common species you encounter.  Indeed this is the basis for making progress in studying any taxonomic group, by focusing on a few common ones first.    

Dogbane beetle
A new picture identification guide ("Beetles of Eastern North America" by Arthur Evans) is very handy in determining which family and perhaps species you may be looking at.  A knowledge of plants can facilitate this process.  For example I noticed some strikingly iridescent beetles on dogbane (Apocynum), a close relative of milkweed.  Indeed the beetles are dogbane beetles (Chrysochus) which feed on the poisonous dogbane and utilize the toxins for defense, and advertise their toxicity by their spectacular colors (due to structural refraction of light).  

Elderberry borer
Similarly the brightly colored elderberry borer, a gorgeous longhorn beetle that feeds on toxic elderberry, advertises its distastefulness by bright colors.  This may surprise you since people can eat the flowers and ripe fruits of elderberries. This is also a lesson in the consumption of wild plants- never eat anything that has brightly colored insects feeding on it ! 

Longhorn beetle
Another longhorn beetle that I found is the exact opposite- very cryptic. This white-spotted sawyer feeds on white pines in our area and escapes predation by its camouflage.

One of the most remarkable moths is a day-flying species called the hummingbird clearwing sphinx which has recently appeared in our yard.  It hovers in front of flowers and drinks nectar just as do the hummingbirds. Its high energy lifestyle requires it to work hard to obtain the necessary energy and you can see this in the frantic way it flits from flower to flower.  Its coloration resembles a bumblebee which may offer it some protection from bird predation, especially when temperatures are too cool for it to fly.

Hummingbird clearwing sphinx on wild bergamot
While trimming a red oak tree I came across a moth caterpillar that epitomizes camouflage as a strategy. This is the caterpillar of the dotted prominent moth which hides from predatory birds by its green coloration among the oak leaves. The longitudinal yellow line may help to disrupt the outline of the caterpillar as do the red spots around each spiracle (the entrances to the tracheal system by which it breathes) and the knobby appearance of the skin.  If attacked, the caterpillar is said to expose large yellow mandibles as a threat.

So  who can deny that the insects are a fascinating if somewhat bewildering group of creatures?  Let us all attempt to be more catholic in our interests in the natural world.  Such an approach will repay us with a multitude of fascinating information and simple awe concerning the amazing creatures with which we share the planet.  

Bill Dunson 
Galax, VA and Englewood, FL

No comments:

Post a Comment