4 October 1994
Volume 2: no. 10
The recent cold front has slowed the insects down some, but there are still some critters around, we just have to look a little harder. Sugar baits and black lights will still work well, especially on those warm nights which we will still have. One of our young readers recently wrote with a question about preserving immature insects, especially larvae. Immatures are preserved in alcohol. Ethanol is usually best, but 70% rubbing alcohol can also be used. We can prevent the larvae from fading and the alcohol from becoming discolored by dropping the larvae in boiling water for about 30 seconds and then transferring them into alcohol vials. Glass vials with screw tops are best for preserving and displaying immature insects. These items may be obtained from biological supply houses like BioQuip, NASCO, or Wards etc. Vials might be available locally at pharmacies, though the vials they have are usually larger than you would want in your collection. If you know a druggist really well, you might get him to order some smaller vials for your use.
Catching the big one:
Almost everyone dreams of finding those large beautiful moths which we see in individual mounts or of catching beautiful butterflies in exotic places. Those dreams are attainable with a little perseverance and attention to detail. Many of these insects can be reared from eggs, larvae, or even pupae and at times these are more easily obtained than the adult. Begin by learning the plants the insects are attracted to for feeding and egg laying. ( We have published lists of butterfly plants in former issues of the Gloworm. This fall and winter we will review some of those and add to the list especially for moths.) Check those plants for presence of the immature forms, eggs or larvae. Check in the soil underneath those plants for pupae. When you are blacklight trapping or sugar baiting, keep the female moths alive to try your hand at getting them to lay eggs (oviposit). Generally, a female moth will have a stouter abdomen than a male and usually have a larger body and wing span than the male of the same species. Females' antenna are thinner and less feathery than the males'. Some species are sexually dimorphic, meaning that the male and female differ drastically in color, in markings or both. Some insects are seasonally dimorphic, i.e. they change in color or markings from spring to midsummer.
Don't worry about trying to get the moths to mate, most moths we capture at lights or bait stations will already be mated. The female will usually lay eggs if confined in a brown grocery bag with the top rolled over two or three turns and fastened closed with a clothes pin. The moth will glue her eggs to the inside of the bag or simply drop them in the bottom. The eggs vary greatly in color, size, and even shape from species to species. Some eggs will be laid singly while others will be in clumps. Hatching time varies as much as the color. Most moth eggs hatch in from 3-14 days (some eggs hatch the following spring). Almost all eggs will turn darker a few hours before hatching. If the egg walls collapse and the eggs shrivel and dry up, the eggs are infertile.
EGGS: Cut the paper on which the eggs are glued away and place them in a clear plastic box or empty pill container. Place them in an area where they will be seen more than once per day so that the larvae will be seen as they hatch or soon after. Do not place leaves or water in the container with the eggs. If you collected the moth, study its life history and try to identify its host plant, then locate a good supply of food plants. Eggs which are to be overwintered can be held in a pill box or closed container in the refrigerator over the winter (35-40 deg F). Eggs or larvae which were collected should be fed the plant material on which they were located.
The larvae which emerge from the eggshells are very tiny. Some eat only enough of the shell to get out, others eat the entire eggshell. Many of the small larvae will not begin eating for 12 to 24 hours after emergence. None of the larvae can live much longer than 24 hours without feeding so it is very important that the eggs be checked daily prior to hatching. The caterpillars may be kept indoors in refrigerator storage boxes with tightly fitted lids. Transparent durable plastic is best. Place paper towels or tissue on the bottom of the `cage' to catch the frass. The entire larval cycle can be completed in a `cage' which is 10X14X4 inches. (These can be obtained at most hardware or discount stores.) As long as the `cages' are opened daily, there is no need to drill air holes in them. Place the food plants in the `cage' and using a small camel's hair brush transfer the tiny larvae to them. Many small larvae can be started in one box, but as they grow they should be separated out so that there are no more than 4-8 larvae in a single `cage'. Fresh food daily is important, but cleanliness is a necessity. Change the towels often and keep excess moisture from collecting on the sides of the cage. Diseases will kill the larvae quickly if allowed to develop. `Cages' should be washed with clorox solution between uses. Once the larvae accept the foliage and begin feeding, it is best to keep them on that foliage throughout their cycle. Simply place fresh foliage in the cage and the larvae will move to it on their own. You can remove the bare branches as you place new food into the cage. Use the food sparingly, the leaves should not be stuffed into the cage. Larvae need room to move around. Do not place wet leaves in the cages. If the specific host of a moth is not known for an area, experiment with batches of larvae by offering different `cages' different sets of foliage. The insects may be grown outdoors during the spring and summer. This can be accomplished by using a sleeve. Construct the sleeve from curtain material or cloth screen. (See drawing of sleeve cages) The sleeve is drawn over a branch of the food plant and securely fastened on both ends. Eggs or newly hatched larvae are placed inside to feed naturally without threat of parasites or predators. Watch the larvae grow and go through their changes. The different stages of development for the caterpillars are called instars.
First instar larvae are very small and as they grow they molt, shedding their skin, to pass into another instar. Some species pass through as few as 3 instars while others may have up to 6. Most of the moths and butterflies will have 5 instars. Near the end of the last larval instar the larvae will void their digestive tract of juicy frass and begin to change in form slightly. Some will seek to burrow beneath the paper towel or leaves in their cage. Caterpillars that spin cocoons will begin that process by attaching silken threads to leaves or other objects. Allow the cocoon spinning process to occur undisturbed. After it is completed the cocoon can be remove from the cage and air dried for a couple of days. Moths which form bare pupae should be placed in a small covered box by themselves as they begin to `get fat' and change. A paper towel should be place in the box to absorb any moisture. Change the towel if it becomes soiled or damp. Do not handle the pupae, or jar the container during this process before it has time to harden. It is very difficult to hold insects overwinter. Hibernating butterfly pupae may be held in the refrigerator if they are kept in a tightly-closed container with a damp paper towel. The towel should be changed periodically. Diseases and mold can kill the pupae.
PUPAE: After the initial pupal period (3-4 days), the pupae may be handled. Many of them will wiggle if held in your hand, but hey should not be squeezed too much. Cocoons (a covering which some species construct to protect the pupae) should be left in a safe place in the open air for about a week to dry and harden and to allow the pupae to completely form inside. Once the pupae have formed, it may be only 2 to 3 weeks before moths emerge. If you want to save the pupae in the cocoons through the winter they should be left outdoors in the cool or they may be stored in the plastic cages and kept in the refrigerator until spring. (Do Not Freeze Them). Remove leaf wrappings or other items which might mold. Keep the boxes fairly dry to help prevent disease and mold. The cocoons can be removed to room temperature when you are ready for them to emerge. An emergence cage can be constructed from a cardboard box with clear plastic, cheesecloth or screen glued across it to allow observation. Do not dampen the cocoons. Place the cocoons on the floor of the box and back off to watch. DO NOT ASSIST THE INSECTS IN THIS PROCESS. Bare pupae should be handled differently from pupae in cocoons. After they have hardened each pupa should be rolled in a strip of facial tissue or paper towel. These can be stored in a plastic box, buried in sterile peat moss or potting soil. Tape the box closed and hold the pupae in the refrigerator until time for them to emerge. A large crisper chest can be used as an emergence chamber. Place water saturated paper toweling (3 to 4 layers) in the bottom of the chamber. Wrap each pupa individually in a wet paper towel and lay it on the bottom of the chamber. Place another wet towel over the pupae and close the chamber. A piece of cheese cloth should be attached to the side of the chamber so that emerging insects will have a place to rest. Insects reared in unheated buildings have a better chance of surviving than those held in a refrigerator.
ADULTS: The moth and butterflies must struggle to emerge or they will not develop properly. It may take more than an hour for some of them to emerge completely. Moths must find something to crawl up on. The wings must hang downward for them to fill out . The moths/butterflies often take 2 to 3 hours to completely dry and harden. In order to repeat the cycle, you must successfully raise a male and a female and get them to mate. This can be done in the emergence cage or in a larger screened cage. Set the cage outside at dusk and leave it out all night. The moths will generally mated sometime during the night. Now you can repeat the process. This information was gleaned from `Growing Moths' by Robert Dirig, 4-H Members' Guide #M-6-6, New York State College of Agriculture, Cornell University.
Dr. Michael R. Williams
Entomology & Plant Pathology
Mississippi State, MS 39762-9775
phone - 601-325-2085
home - 601-323-5699
FAX - 601-325-8837