Handling Berlese Collections.—In the field, put samples of leaf mold or other material in tightly woven cloth bags or strong paper bags for transportation. It is convenient to have small paper bags for mushrooms, nests, and other small items, and larger bags for ground cover, moss, and the like. When collecting ground cover and similar material, put in each bag enough of a sample so that it will not shake around loosely, but do not pack it tightly. Be sure that samples do not overheat while being transported.
Samples may be collected at any season. If collected during warm weather, they should be taken to a laboratory and placed in the funnels within a day or two; otherwise, considerable loss of population occurs within the samples. If collected during cold weather, they may be kept in cold storage for a week or two with little loss of fauna.
In putting material in the funnel, lay it carefully on the screen to a depth of a few inches. Moss and sod should be placed upside down in a single layer on the screen. In the case of dense material, pile the sample chiefly around the sides of the funnel and leave an opening in the middle, as shown in [fig. 7]. After the funnel is loaded, place it in the rack, put the bottle of preservative under it, and apply the heat.
By substituting a different kind of collecting bottle at the bottom of the funnel, you may obtain live material for rearing. The exact changes necessary to obtain live material will depend upon your ingenuity and the type of material you desire.
Equipment for Collecting Aquatic Insects
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.