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Rearing Different Kinds of Insects

Even the collector of insects who cares little about habits and life histories desires often to rear his specimens, since they are then in the best condition for the collection; and then, too, it is very difficult sometimes to capture some kinds of insects, or they can be obtained only in this way. The methods of rearing caterpillars in order to obtain the adult butterflies or moths has been admirably treated by Dr. Holland in his "Butterfly Book," and the breeding cages recommended by him may be used equally well for many of the insects described in this volume. The simplest form of such cage is frequently the best, and, as Dr. Holland says, with some species the best method is simply to pot a plant on which the insect is known to feed and place it in a box over which some mosquito netting is tied. Glass cylinders or even lamp chimneys placed over small plants growing in pots, the top being covered with gauze, are frequently used to advantage in this work, and glass jars--from the small test-tube to the large morphine bottles and fruit jars and up to the large battery jars--all may be used in rearing different kinds of insects. The large, so-called Riley breeding cage, shown at Figure 256, is a good one, especially if it is used with the improved base invented by Professor Comstock, shown at Figure 257. Some very good breeding jars are sold by the dealers in entomological supplies, but most workers prefer to construct their own cages.

All earth used in rearing insects in the cages or in the bottles should be sterilized and sifted. This is necessary in order to destroy disease germs, in order subsequently to regulate the amount of moisture, and in order to destroy predaceous mites and other insects which might be the cause of damage or confusion. In my office we prepare earth readily and in bulk in a galvanized iron oven 2 1/2 X 1 1/2 X 1 foot. The cover is roofshaped, and lifts off by a central handle. There is a circular orifice in this cover to emit steam and facilitate drying. The oven stands on legs and is heated by a single gas jet from a Bunsen burner placed beneath. After two hours' heating the moisture becomes dissipated, and the earth becomes dry and is readily sifted. It is then passed through a sieve, and is in proper condition to use either in large boxes for underground insects or in the ordinary breeding jars and cages.

Professor Comstock has invented and described a root-cage in order to study underground insects. This is a metal cage with glass sides, made narrow, and with galvanized iron additional sides which can be slipped down over the glass ones so as to keep the cage dark when not under observation. Plants and insects are placed in earth between the two glass sides, and the whole apparatus is then placed in the ground. It can be pulled up and the insects watched through the glass.

For insects feeding upon grasses it is well to make a wooden box two feet deep with bottom perforated with a few auger holes covered with wire netting and containing a good supply of growing grass. The box should be of good size, say 2 x 2 x 2 feet. Little upright posts or sticks or laths six inches high should be nailed to the corners of the box, and gauze mosquito netting or something finer tacked over the whole. This kind of a box is of good service in rearing grasshoppers, which are the most difficult insects to rear. Confined in a small breeding cage they feed little, and are apt to fatally exhaust themselves in futile efforts to escape. Boxes for these insects should be about three feet square, and in the earth should be growing not only grasses but also weeds of various kinds. The long-horned grasshoppers (Locustidae) are very easy to rear in confinement, and need only be given an occasional supply of fresh food. This is the case also with the walking-sticks, and mantids, the latter requiring no moisture whatever beyond that which they get from the bodies of their victims.

That reminds me that one of the difficulties encountered in the rearing of insects is the proper maintenance of the right degree of moisture. Galls of all kinds are apt to be left either too dry, in which case the issuing of the insect is delayed far beyond the normal time, or too moist, in which case they become covered with mildew and spoil. If the jar containing them be left open they dry no matter how frequently sprinkled. If it be closed mildew frequently puts in its appearance. This difficulty is obviated by keeping them in a series of jars of the same height, the mouths of the jars being covered with gauze to prevent the escape of the insects or parasites. Over the whole series is laid a large sheet of blotting paper which is moistened daily and the insects seem to thrive under this treatment. In rearing Hymenopterous parasites, the breeding jar should be tightly closed and an occasional strip of moistened blotting paper inserted or they may be enclosed in glass tubes with tight absorbent stoppers the latter being occasionally moistened. Bees need very little moisture and give very little trouble in rearing. Wood-boring insects of all kinds may as a rule be kept perfectly dry or only moistened every two or three weeks. Plant-bugs need simply plenty of fresh food and take care of themselves with comparative indifference as to their surroundings.