Hundreds of different kinds of insects are aquatic and offer rich
collecting possibilities. In all instances, the immature stage lives in
water, but in most of them the adult stage emerges on land or flies in
the air. For this reason several types of collecting are needed to
obtain a good sampling of aquatic insects.
Night Collecting of Adult Insects.--Collecting at lights on warm, cloudy
nights, or warm nights without moonlight, gives best results. Two simple
methods are as follows:
Drive your car to a spot overlooking a stream or lake and turn on the
bright lights. Into a shallow pan, such as a pie pan, pour enough
alcohol to cover the bottom with one-eighth to one-fourth inch of fluid.
Hold the pan directly under a headlight. If aquatic insects are on the
wing, they will come to the light and eventually drop in the fluid,
which traps them. With a small piece of wet cardboard, you can scrape
the entire insect contents of the pan into a small bottle of alcohol,
which you should then label, giving date, name of collector, and
location.
Lights in signs and store windows (especially blue neon signs) near
fresh water attract large numbers of aquatic insects. You may capture an
insect easily by dipping an index finger in a bottle of alcohol,
"scooping up" the insect rapidly on the wet surface, and then dipping it
in the bottle. An aspirator also can be used with success.
Day Collecting of Adult Insects.--During the day, aquatic insects
frequently rest on or under bridges, window ledges, and similar places,
and show a preference for dense trees in shaded situations. They are
especially numerous in those spots where the heavily leaved branches
hang low over the water and form humid, protected areas in the heat of
the day. Here sweeping with a stout and fairly wide-mouthed net is very
effective. Aquatic insects may often be picked off stones in such
places, especially early in the season.
Collecting Larvae.--Practically every stream or lake has some aquatic
insect larvae which may be collected by various methods, some simple and
others requiring specialized and complicated apparatus. For general
collecting, the following suggestions may be of value:
1. Look under logs and stones. Search out crevices in them; some insects
hide away and demand of the collector a keen and careful search.
2. Tear apart bunches of leaves, roots, and other debris that may have
piled up in front of a rock or log, or that may have accumulated at the
end of a root or branch dangling in the water.