Collecting and Preserving

specimens may be badly rubbed or torn. If only smallinsects are desired, they may be protected from damage bylarger insects by placing a screen with the proper sizedmesh over the entrance. The Minnesota trap is very similarto the New Jersey trap, but it does not include a fan or anymotorized method of draft induction.The Wilkinson trap (fig. 14) requires somewhatmore effort to construct than the preceding traps, but it hasthe advantage of confining, not killing, the trapped insects.Moths, therefore, can be collected in good condition if thetrap is inspected frequently and desirable specimens areremoved quickly through the hinged top and placed in akilling jar.Several highly effective but more elaborate deviceshave been made for collecting moths and other fragileinsects in good condition. Basically, they all use theprinciple of a funnel with a central light source above itand vanes or baffles to intercept the approaching insectsthat are dropped through the funnel into the containerbeneath, which may or may not hold a killing agent. Thenature of the container and the type of killing agent affectthe quality of the specimens obtained. Some traps catchthe insects alive in a large collection chamber, such as agarbage can, which is filled or nearly filled with looselyarranged egg cartons. Most moths will come to rest in thecavities between the egg cartons and will remain thereuntil removed in the morning.Other traps are designed to kill the insects by meansof high concentrations of fumes from a liquid killingagent, such as tetrachloroethane or calcium cyanide. Aheaping tablespoon or more of calcium cyanide is placedin each of four to six brown paper bags, which are hung ina large garbage can or other large container. A dampenedcloth, such as a washcloth, is also hung inside the can tohumidify the air and activate the cyanide. This is especiallynecessary in dry weather. The concentration of thegas inside the can is so great that insects are inactivatedalmost instantly on entering, and even the most delicatespecimens are damaged very little. The bags containing thecalcium cyanide powder should be replaced as needed. Iftwo of the oldest bags are replaced with two fresh oneseach successive night, the trap can be run as long as thecollector desires.Handle cyanide outdoors, facing downwind, andwith extreme caution. During the day, when the trap is notin use, store the cyanide bags in an airtight container. Allforms of cyanide used as killing agents react and breakdown quickly when exposed to air and moisture; neverthelessdispose of the residue carefully.To prevent rainwater from accumulating in the trap,place a screen-covered funnel inside the collectionchamber to drain the water out through a hole in theTechniques and Toolsbottom of the trap. Sometimes a system of separators isadded to guide beetles and other heavy, hard-bodiedinsects into a different part of the container than the mothsand other delicate specimens.The most efficient light traps use lamps rich in theiroutput of ultraviolet light. The British-made Robinson trapemploys an intense, blue-white, 125-watt mercury vaporlamp of a type used for street lighting. This, the mosteffective insect attractant commercially marketed, iswidely used in many kinds of light traps because it hassome special advantages over other kinds of attractants.For example, this type of lamp is the only one that emitsthe kind of light that attracts large numbers of Catocala(underwing) moths, a colorful group popular with manycollectors.Many traps are equipped with 15-watt ultravioletfluorescent tubes, which emit a highly visible bluish-whitelight, although blacklight tubes emitting deep purple lightare similarly effective. Ultraviolet tubes of lower or higherwattage also may be used and are all highly effective. A15-watt ultraviolet tube has been estimated to attract about10 times as many insects as a 500 candlepower gasolinelantern or incandescent lamp. The advantage of thefluorescent tube over the mercury vapor lamp is that it isless expensive and much more portable. A 15-watt tube iseasily powered by an ordinary automobile battery by usingan inverter to change 6- or 12-volt direct current to 120-volt alternating current. Also, its ultraviolet output is notstrong enough to cause any significant eye damage. Thesafety factor of the mercury vapor lamp at close range isless certain, although entomologists who have used theRobinson trap for many years seem to have suffered no illeffects.A new, lightweight, spillproof 12-volt battery, inwhich the acid electrolyte is a gel rather than a liquid, isfar superior to the standard automotive battery for poweringlight traps, but it is fairly expensive and requires aspecial charger. Special lightweight, nickel-cadmiumbattery packs, used to power blacklights for collecting, aremarketed by some dealers of entomological equipment.1.10.10 Light SheetsAnother highly effective method of using light toattract moths and other nocturnal insects is with a lightsheet (fig. 15). This is simply a cloth sheet, usually a whitebedsheet, hung outdoors at night with an appropriate lightsource or combination of sources such as ultravioletfluorescent tubes, gasoline lanterns, or automobileheadlights placed a few feet in front of it. As insects areattracted and alight on the sheet, they are easily captured incyanide bottles or jars by the collector who stands inattendance or at least checks the sheet frequently. The17