Northern Prairie Wildlife Research Center
Numerous techniques may be used for collecting moths. One of the most productive approaches is to collect moths from a white sheet placed under or behind an ultraviolet light at night. The moths are attracted to the light and will come to rest on the sheet where they can be easily observed and placed into containers if specimens are desired. A light trap can be assembled so moths may be collected during the entire night without being constantly monitored. Attractants other than ultraviolet light can be used as well, such as, white light, halide lights, fermented baits, commercially available manufactured pheromones, and live virgin females. Day-flying moths are best collected with an aerial net such as those used to collect butterflies.
An excellent means of acquiring moths is to capture live adult females and rear the caterpillars that emerge from her eggs. In some species the female must be coaxed into depositing eggs by providing proper conditions of light, temperature, humidity, flying space, and a substrate for oviposition. Also, moths may be obtained by collecting caterpillars from host plants and rearing them indoors in containers or by placing screen sleeves over the foliage of the host plant in the field. In either situation caterpillars may require some attention regarding suitable foliage for feeding, an appropriate site for pupation, and frequent observation for noting the time of adult emergence so the moth does not damage its wings while being contained.
Careful collecting should be conducted to protect habitat where moths and other organisms live. Avoid trampling plants and disturbing unstable soils. Try to grow plants for the food the caterpillars require or at least prune wild plants with care and an understanding that you may need more foliage later. Collect as few moths as your study requires for accuracy and proper documentation. If possible release specimens back into the environment from which they were acquired once your observations are completed. Do not introduce exotic species and be aware of legal obligations regarding collecting on private and public lands. In particular, heed the importance of protecting rare and endangered species.
The rearing of caterpillars or the containment of moths for the acquisition of eggs is helpful in associating the caterpillar life stage with the adult life stage, testing food plants for suitability, or associating parasitoids and diseases.
Rearing indoors has numerous advantages and disadvantages. One advantage is that the specimen is less likely to be lost. Another advantage is that the caterpillar will likely grow faster indoors because of warmer temperatures. However, indoor rearing requires that food must be provided by potted plants, clipped foliage from the field, or artificial diets. Unsuitable rearing conditions will result in high mortality. Temperature control, dehydration, fungal growth, starvation, cannibalism, and overcrowding are common problems. Additionally, the use of closed containers may cause problems due to excessive condensation and poor sanitation. The presence of slightly moistened peat moss is helpful at the time of pupation. The peat moss provides a medium within which the caterpillar can bury itself and the moisture helps to prevent dessication, a major obstacle when rearing in dry indoor conditions.
A color slide or print will provide a record of the moth as a substitute or replacement illustration of a specimen. An excellent photograph can be acquired by using all of the following: (1) A 35 mm, single lens reflex camera with exchangeable lensesCameras with fixed lenses typically will not allow the photographer to get close to the subject or to fill the frame with a small subject. The photographs presented here were taken with a 50 mm macro lens mounted on a 25 mm extension tube. (2) Film with a low ASA rating or a digital camera that is capable of storing the image directly onto a computer diskThe photographs in this book were taken with color slide film ASA 25. This film speed provides superior quality in grain but requires more light than faster films. (3) A flash system, either a bracket or a ring flashThe moths were photographed with a bracket system consisting of two flash units that are mounted on opposite sides of the camera. The lens, film, and flash units allow shooting pictures of moths at f/16 or f/22 at a distance of about 20 mm from the camera lens. Photographs can be taken in the field but shadows, wind, undesirable backgrounds, and other unwanted features (like other insects) may interfere with obtaining the best picture. All of the moths presented in this booklet were field-collected as an adult or reared from a field-collected caterpillar. However, all moths were photographed in a staged indoor setting. The moth was placed on a spreading board, allowed to dry, the pinned and spread moth was then placed onto the end of a thin wooden dowel with a black background.
Moths should be preserved as voucher specimens for eventual study of traits that photographs do not reveal. A properly mounted specimen involves placing an insect pin through the top of the thorax and spreading the forewings and hindwings so that the hind edge of the forewing is at a 90° angle to the body and the front edge of the hindwing is under the forewing so that the tip of the hindwing creates a small notch with the outer edge of the forewing. An excellent example of a nicely spread moth is Acronicta funeralis. An example of a not so perfect but suitable job of spreading the wings of a moth is Hyles lineata (note that the back edge of the forewing is not perpendicular to the body).
The pinned and spread moth will need to dry for a few days at room temperature. Once dried the forewings and hindwings will stay in place and the moth may be removed from the spreading board and put into an enclosed drawer or cabinet for display. A number of problems may occur, specimens will rot if damp, some colors will fade if subjected to direct sunlight, and museum beetles (dermestids) may turn perfect specimens to dust because the beetles eat dead insects. These problems, and others, can be minimized if the moths are stored in sealed containers and kept in a dark and dry location. Labels on the pinned moth should include at least the details of the place and date that the specimen was collected. See Covell (1984) for additional ideas on curating moths.