Keeping Insects in Captivity

Cages. There are many types of containers to use as insect cages. A few simple types are illustrated opposite (especially A-D). An insect can be kept for a time in an empty container (A or B), but it will generally live longer if something like natural conditions are provided.

Plants supplied as food must be kept fresh or regularly replaced.

They can be kept fresh longer if placed in a jar of water, with a cover on the jar around the stem of the plant to prevent insects on the plant from falling into the water (C). Sometimes a plant can be grown in the cage, or a cylinder of screen can be placed over a potted plant (D). Since insects vary greatly in the type of food they eat, the kind provided for a caged insect will depend on the insect's food habits. Insects feeding on other living insects present the major food problems. Whatever the food, generally it must be replaced before it deteriorates.

Many insects, notably plant feeders, need not be provided with water, since they get enough in their food. Others, those feeding on drier foods, may require additional moisture, and a wet sponge or piece of cotton in the cage or a vial of water plugged with cotton and lying on its side can supply it. Take care to avoid an excess of moisture; this promotes the growth of mold, and droplets of water on the walls of the cage may trap insects.

It is often effective to approximate natural conditions in the cage by having sand, soil, or stones, and a plant or some object on which the insect can rest. If an insect being reared requires special conditions for pupation (soil or debris), these conditions should be provided.

Sometimes the best way to have caged insects under conditions as natural as possible is to cage them in the field in their normal habitat. Insects feeding on a plant can be caged in a bag or cylinder placed over the part of the plant on which they are feeding (F). Aquatic insects can be reared in cages partly submerged in their habitat; the screen of such cages should be fine enough to contain the insects but coarse enough to allow food material to get in.

Rearing. Rearing adults from immature stages enables one to follow the insect's life history, and provides the collector with excellent specimens for a collection. Many insects can be reared relatively easily.

A box like that shown in E can be used to rear adults from larvae living in debris or other materials. This material is put into the box and the box sealed; the emerging adults are usually attracted to light, and go into the vial.

Caterpillars are good insects to rear, since many are large and easily observed, and their transformations are very striking. The chief problem is providing suitable food, because most caterpillars feed on only a few kinds of plants. If the food plant is not known, you must either identify the caterpillar and determine its food from a reference book or try a number of plants in the hope of finding something the caterpillar will eat. The food plant can be kept fresh by placing it in water, as described above (C). If the caterpillar requires special condition for pupation (soil or debris), these conditions should be provided.

A caterpillar collected in the fall may overwinter before pupating, or it may overwinter as a pupa; sometimes it may not complete its development unless it is subjected to low temperatures. Cocoons collected in the fall and brought indoors may fail to develop, either because they dry out or require exposure to low temperature. Drying can be prevented by placing the cocoons in a container with a little soil and occasionally sprinkling the soil with water. Exposure to low temperature can be accomplished by placing the cocoons in a refrigerator for a few weeks, or by keeping them outdoors (for example, on the outside windowsill of a room).

Many aquatic insects, especially those living in stagnant water and feeding on microorganisms or debris, are easily reared indoors. They can be reared in some of the water from which they were collected, often without special equipment to aerate the water and without adding more food. If a stream-inhabiting insect is put into an aquarium, the water usually must be aerated and its temperature not allowed to go too high. Adult mosquitoes can be reared from larvae or pupae in containers as small as vials; cover the vials (with netting or a plug of cotton) to prevent the adults from escaping. Predaceous insects such as dragonfly or damselfly nymphs require other insects or small aquatic animals as food, and the aquarium must contain something extending out of the water — a stick or piece of screen — onto which the nymphs can climb when they are ready to transform into adults.

Meal-infesting insects generally are very easy to rear or maintain from generation to generation, since they normally live indoors and do not require extra moisture. They can be kept in containers of their food material; this material should be sifted at intervals, and the insects transferred to a fresh batch.

Spiders, and predaceous insects such as mantids or dragonfly nymphs, will prove interesting to keep in captivity if supplied with suitable insects as food. Many of these animals have unusual methods of capturing their prey. Caged spiders can be watched making their webs or egg sacs.

Adult crickets sing readily in captivity, and live a fairly long time; you can enjoy their songs and also see how the songs are produced. Chicken mash or ground-up dog food can be used as food, and a wet sponge or piece of cotton will provide adequate moisture.

With a little knowledge of an insect's food habits and habitat requirements, an ingenious student should be able to devise methods of rearing almost any type of insect. Anyone rearing adults from immature stages will sooner or later get parasites instead of the adults expected, and thus will learn something about the habits and hosts of parasitic insects.

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