DIPPER DELIGHTS

by John J. Smith

Most of us in the mosquito control field have spent more time than we care to think about wandering around wetlands sampling for mosquito larvae with our trusty dippers. So many times we see creatures that we have not seen before or are not able to identify. I find the creatures which live in the aquatic environment fascinating. It is almost as if you have been teleported onto another planet inhabited by a totally unique assemblage of creatures as foreign as those living at the bottom of any oceanic rift valley.

I am especially intrigued by the invertebrates such as the crustaceans, annelids, insects and yes, you can even observe examples of the sponges and hydras. I can remember as a kid spending most of my time while supposedly skating, actually on my hands and knees with my face inches from the transparent ice watching the caddisfly larvae struggling with their cases as they traveled across the submerged vegetation. I did not get much exercise but it did open my eyes to the fact that life goes on even when the temperatures drop and the snow flies.

I have often corrected people when they would say that there are no mosquitoes around in the middle of winter when in fact there are millions of mosquitoes around they just happen to be in the egg stage. As a kid I always thought that the invertebrates were destroyed by the freezing temperatures of winter and always curious as to how they recovered the next spring. My answer awaited me on the first semi-warm winter day when the sun would heat the sheltered areas around my house and I would observe house flies and queen wasps lethargically sunning themselves. I would turn over rocks in mid February and find a myriad of invertebrates busily performing the art of survival under the most inhospitable conditions. I think this is when my interest in invertebrates began, resulting in many years of observations while involved with research at the University of Connecticut and post-grad at Northeastern University. The same intense interest continues while sampling mosquito larvae during preparations for larval control operations in Norfolk County, Massachusetts.

For the benefit of those who may not have a background in invertebrate zoology, I thought I would take a short journey through the world of the freshwater wetland identifying some of the creatures which I find so fascinating when dipping the wetlands of New England.

Most abundant in almost any dip are the copepods. There are too many species to describe here but one observation I can make is that they always seem to be pregnant (Seems that is what they do best). That is probably why you always find them in such large numbers.

Another frequent capture in the dipper is the amphipod sometimes referred to as a side swimmer. Very often these inhabitants take on vivid colorations of green and pink. They are very fast swimmers and can make for real aggravation when trying to observe under the scope.

Isopods are also found in great numbers in most of the same habitats as mosquitoes. Many may know the terrestrial version which is very often called a pill bug even though it is not an insect. (As a kid I had a much more technical name...army tanks.)

Among the other more common crustaceans found in the New England wetlands are the Ostracods, the Cochostracans, the Cladocerans (we all know Daphnia - the water flea) and the Branchiopoda represented by the fairy shrimp which is a common tropical fish food. Look at these creatures under the scope and it looks as though these tiny armored arthropods are held together with riveted plates. Fascinating alien life right in your own back yard.

Of course the insect world is well represented in the wetlands of New England. There are too many to fully discuss here so I thought I would only consider those that are the most common.

In the spring just as the ice is disappearing from the inner reaches of the northeastern wetland large numbers of the mayfly nymph begin to fill the dipper with their rhythmically undulating abdominal gills. Why they call these aquatic inhabitants mayflies is beyond me for most are on the wing in April (maybe nobody told them!!!).

Along with the mayflies and in slightly less stagnant water is the stonefly larvae which is more commonly found in the same habitats as the dreaded blackfly larvae. (You have to be quicker than the trout if you want to see one of these!)

Less commonly found but always a thrill when captured in the dipper is the dragonfly and damselfly nymphs which we should develop a strong bond with for these creatures share a common interest in wiping out mosquito larvae. Though their ineffectiveness in controling large numbers of mosquitoes is evident, their efforts should be applauded. Of interest is the dragonfly's ability to expell water from the rectum for rapid escape (never try this at home without proper training).

As mentioned above the caddisfly also shares the aquatic habitat with the mosquito. I find the varied styles of case making intriguing and wonder why some species use pebbles while others use leaves. (Does one know something the other doesn't or does the pebble siding company do more advertising?)

I could go on forever describing the diving beetles, the whirligig beetles, the backswimmers, the water striders ( I would love to be able, as a mosquito control officer, to walk on water...life would be so much simpler), the giant water bugs (sounds like a class B horror flick...they bite by the way...just found that out recently) and many, many more. One of my favorites is the springtail which is sometimes called the snow bug in New England because of the large numbers frequently found on snow during warm winter days.

Lets not forget the annelids such as the horsehair worm and everyone's favorite the leech (which brings out as much fear as "jaws" in many - usually resulting in a hasty retreat out of the wetland).

The flatworms are well represented in the dipper by the laboratory favorite planaria.

Finally I recently found examples of freshwater sponges and hydras. That made my day. I have read about freshwater examples of these but had always thought they were going the same route as the freshwater mussel. As a kid, I use to fish by the old mill site in Walpole, Massachusetts but spent most of my time investigating the mussel beds down stream. Most of the mussels are gone now but I can report that I have seen more in recent years which I hope is a sign of recovery.

There are so many fascinating creatures inhabiting the New England wetlands, so many that I could never mention them all but the next time you go out dipping take a little closer look at what else is out there. Many times I will take my trusty, cleaned-out peanut butter jar (my hi-tech, low-cost laboratory collecting device) with me and bring back some of these inhabitants to show anyone interested. You would be surprised how interested the commoner will be. I have often brought samples along with me when visiting the various school systems across Norfolk County. The students in the elementary schools are especially impressed. Seeing them eyeball to eyeball with these creatures brings back the memories I have of sliding across the ice in my back yard pond following the travels of my newest find under the frozen world of the New England winter.

by John J. Smith, Superintendent

Norfolk County Mosquito Control Project

Norwood, Mass.

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