Collecting and Preserving

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Carnivorous insects should be given prey similarto that which they normally would consume. This diet canbe supplemented when necessary with such insects asmosquito larvae, wax moth larvae, mealworms, maggots,or other insects that are easily reared in large numbers incaptivity. If no live food is available, a carnivorous insectsometimes may be tempted to accept a piece of raw meatdangled from a thread. Once the insect has grasped themeat, the thread can be gently withdrawn. The size of thefood offered depends on the size of the insect being fed. Ifthe offering is too large, the feeder may be frightenedaway.Bloodsucking species can be kept in captivity byallowing them to take blood from a rat, mouse, rabbit, orguinea pig. A human should be used as a blood source onlyif it is definitely known that the insect or mite being fed isfree of diseases that may be transmitted to the human.Stored-product insects and mites are easily keptalive and breeding in containers with flour, grains,tobacco, oatmeal or other cereal foods, and similarproducts. Unless leaf-feeding insects are kept in flowerpotcages where the host plant is growing, fresh leaves fromthe host plant must usually be placed in the rearing cagedaily and old leaves removed.1.13.2.6 - Artificial DietsSome species can be maintained on an artificial diet.The development of suitable artificial diets is complex,involving several factors besides the mere nutritional valueof the dietary ingredients. Because most species of insectsand mites have very specific dietary requirements,information regarding artificial diets is found mainly inreports of studies on specific insects or mites.1.13.3 - Special Problems and Precautions inRearing.Collecting and Preserving Insects and MitesProblems may arise in any rearing program. Cannibalism,for instance, is a serious problem in rearingpredaceous insects and necessitates rearing specimens inindividual containers. Some species resort to cannibalismonly if their cages become badly overcrowded. Disease isalso a problem. It can be caused by introducing anunhealthy specimen into a colony, poor sanitary conditions,lack of food, or overcrowding.Cages should be cleaned frequently and all dead orunhealthy specimens removed. Use care not to injurespecimens when transferring them to fresh food or whencleaning the cages. Mites and small insects can be transferredwith a camel’s hair brush.Attacks by parasites and predators also can bedevastating to a rearing program. Carefully examine thehost material when it is brought indoors and before it isplaced in the rearing containers to lessen the possibility ofpredators and parasites being introduced accidentally.Also, place rearing cages where they will be safe fromants, mice, the family cat, and other predators.References (rearing): Banks et al. 1981; Clarke1941; Fincher & Stewart 1968; Furumizo 1975; Gerberich1945; Harwood & Areekul 1957; Hodgson 1940;Krombein 1967; Levin 1957; Merritt et al. 1978; Peterson1964; Sladeckova 1962; USDA 1970.Part 2. - Specimen Preservation2.1 - Liquid Agents for Killing andPreservingInsects and mites of all kinds may be killed andpreserved in liquid agents, but it is first necessary todetermine the advisability of using a liquid killing agentrather than a dry gaseous agent. Some kinds of insects arebest kept dry; it may not be advisable to allow others tobecome dry. Directions for the treatment of various insectsare given in the last part of this publication under thevarious orders.Fig. 16. Lepidoptera temporaily stored in paper andglassine.Ethanol (grain or ethyl alcohol) mixed with water(70 to 80 percent alcohol) is usually the best generalkilling and preserving agent. For some kinds of insects andmites, other preservatives or higher or lower concentrationsof alcohol may be better. Because pure ethanol isoften difficult to obtain, some collectors use isopropanol(isopropyl alcohol) with generally satisfactory results.Isopropanol does not seem to harden specimens as muchas ethanol, and at least it is satisfactory in an emergency.Although there is controversy over the relative merits ofethanol and isopropanol, the choice of which to use is notso important as what concentration to use. This choice24
depends on the kind of insect or mite to be preserved.Parasitic Hymenoptera are best killed and preservedin 95 percent alcohol. This high concentration prevents themembranous wings from becoming twisted and folded,hairs from matting, and soft body parts from shriveling.This concentration may also be desirable if large numbersof insects are to be killed in a single container, such as inthe killing jar of a Malaise trap, because the insect bodyfluids will dilute the alcohol. On the other hand, softbodiedinsects, such as aphids and thrips, small flies, andmites, become stiff and distorted if preserved in 95 percentalcohol and should be preserved in alcohol of a lowerconcentration. Adult bees should not be collected inalcohol because their usually abundant body hairs becomebadly matted. Adult moths, butterflies, mosquitoes, mothflies, and other groups with scales and long, fine hairs onthe wings or body may be worthless if collected in alcoholregardless of the concentration.Formalin (formaldehyde) solutions should not beused because the tissues become excessively hardened andthe specimens then become difficult to handle.Larvae of most insects should be collected in alcoholand subsequently killed in boiling water to “fix” theirproteins and prevent them from turning black. Larvaeshould be left in hot water for 1-5 minutes, depending onthe size of the specimens, then transferred to 70-80 percentalcohol. Large specimens or small specimens that havebeen crowded into one vial should be transferred to freshalcohol within a day or two to reduce the danger ofdiluting the alcohol with body fluids. If the alcoholbecomes too diluted, the specimens will begin to decompose.Water is not a preservative.For some groups, preservation is better if certainsubstances are added to the alcohol solution. Thrips andmost mites, for example, are best collected in an alcoholglycerin-aceticacid (AGA) solution, and for many larvae akerosene-acetic acid-dioxane (KAAD) solution is preferred.If KAAD is used, larvae need not be killed inboiling water. Formulas for these and other solutions aregiven in the Appendix.For some histological, cytological, or physiologicalstudies, specimens must be in a certain critical conditionand must be preserved in special media (see Walker &Boreham 1976).Techniques and ToolsMany insects collected in alcohol are later pinned forplacement in a permanent collection. Hardbodied insectssuch as beetles can be pinned directly after removal fromalcohol, but for them and all softer insects such as flies andwasps special procedures must be followed.2.2 - Temporary Storage of SpecimensAfter specimens have been collected, time is oftennot immediately available to prepare them for permanentstorage. There are several ways to keep them in goodcondition until they can be prepared properly. The methodused depends largely on the length of time that thespecimens may have to be stored temporarily.2.2.1 - Refrigeration and FreezingMedium to large specimens may be left in tightlyclosed bottles for several days in a refrigerator and stillremain in good condition for pinning as will smallerspecimens if left overnight. Some moisture must bepresent in the containers so that the specimens do notbecome “freeze-dried,” but if there is too much moisture, itwill condense on the inside of the bottle as soon as itbecomes chilled. Absorbent paper placed between the jarand the insects will keep them dry. When specimens areremoved for further treatment, place them immediately onabsorbent paper to prevent moisture from condensing onthem.Insects may be placed in alcohol, as describedpreviously, and kept for several years before they arepinned or otherwise treated. However, it has been shownthat many insects, especially small ones, can deteriorate inalcohol stored at room temperature. Long term storage ofspecimens that suffer from this kind of deterioration can belessened by storing the containers in a freezer. Eventhough the alcohol will not freeze at the temperaturesobtained by most ordinary freezers, the lower temperatureseems to slow or stop deterioration of the specimens.Larvae and most soft-bodied adult insects and mitescan be kept almost indefinitely in liquid preservatives;however, for a permanent collection, mites, aphids, thrips,whiteflies, fleas, and lice usually are mounted on microscopeslides (see p. 36). Larvae are usually kept permanentlyin alcohol, but some may be mounted by the freezedryingtechnique (see p. 34) or by inflation (see p. 34).Fig. 17. Alcohol storage jars.25
Page 1 and 2: Techniques and ToolsCOLLECTING AND
Page 3 and 4: 5.6 - Placing the Labels...........
Page 5 and 6: the insects, using nets, aspirators
Page 7 and 8: grooves as deep and as wide as the
Page 9 and 10: flammable and should not be used ne
Page 11 and 12: Bradbury & Morrison 1975; Clifford
Page 13 and 14: attracted to the light and humidity
Page 15 and 16: Techniques and ToolsHeathcote 1957;
Page 17 and 18: specimens may be badly rubbed or to
Page 19 and 20: pulled, a spring-loaded canopy is s
Page 21 and 22: & Savage 1967; Davidson & Swan 1933
Page 23: foods also require very little mois
Page 27 and 28: group to another. For example, spid
Page 29 and 30: most convenient; clear plastic sand
Page 31 and 32: or placed on triangles after this t
Page 33 and 34: place the tip of the minuten with t
Page 35 and 36: with minuten through the thorax wit
Page 37 and 38: hindmargin of the forewings should
Page 39 and 40: now in use at most museums and othe
Page 41 and 42: pellets in about 10 ml of water may
Page 43 and 44: to see if there is movement of the
Page 45 and 46: wings carefully with a fine brush o
Page 47 and 48: 5.5 - Label DataThe indispensable d
Page 49 and 50: oxes are available in sizes made to
Page 51 and 52: mens to prevent them from rotating
Page 53 and 54: ReferencesA’Brook, J. 1973. Obser
Page 55 and 56: methods, pt. 11, Notes on collectin
Page 57 and 58: Ann. Entomol. Soc. Am. 69:287-288.G
Page 59 and 60: Jacobson, M. 1972. Insect sex phero
Page 61 and 62: collection and rearing container fo
Page 63 and 64: possible host stimulant to mosquito
Page 65 and 66: Townes, H. K. 1972. A light weight
Page 67 and 68: AppendixFormulas Distilled water sh

Collecting and Preserving

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