The Dobsonflies, Fishflies, and Alderflies (Megaloptera)

Stream Team Academy Fact Sheet #19

Life Cycles & Natural History of Aquatic Insects Part 7 – The Dobsonflies, Fishflies, and Alderflies (Megaloptera)

Stream Team Academy An Educational Series For Stream Teams To Learn and Collect Fact Sheet Series #1 Tree Planting Guide By Paul Calvert #2 Spotlight on Big Muddy he Megaloptera is a small order light for a period of time before settling #3 Lewis & Clark comprised of two families, the to the bottom, while the corydalids show #4 Missouri Is Number One? T Corydalidae (dobsonflies and fishflies) and no photopositive tendencies, burrowing #5 Responsible ATV Use the Sialidae (alderflies). They are closely quickly into the substrate immediately #6 Headwater Streams #7 Whatology? related to the Neuroptera (lacewings after hatching and dropping. and spongillaflies), and were previously Megaloptera are holometabolous, #8 Exotic Does Not Mean Beauty #9 Wetlands lumped together with that order. Unlike undergoing a complete metamorphosis. #10 Stream Sedimentation the Neuroptera, all Megaloptera larvae Larvae go through 10 to 12 instars before #11 Emerald Ash Borer Found in are aquatic and they include some of the crawling out of the water and onto the Missouri largest aquatic insects. The larvae of bank to pupate. Some have been reported #12 Protecting Prairies = the corydalids are sometimes known as to travel over 150 feet from the water’s Protecting Streams hellgrammites or toe biters. edge to accomplish this feat. Some #13 Life Cycle & Natural History of Aquatic Insects (Part 1) species produce pupal chambers under Life Cycle stones, stumps, or detritus; others in dry #14 Life Cycle & Natural History of orydalids use scent in their mating Aquatic Insects (Part 2) streambeds or the soil. Megaloptera pupae rituals, while the sialids use acoustical #15 Life Cycle & Natural History of C have free appendages and the abdomen Aquatic Insects (Part 3) signals like abdominal vibrations or is movable, a form known as exarate. In #16 Life Cycle & Natural History of tapping, similar to stoneflies, for mate most holometabolous insects, the pupae Aquatic Insects (Part 4) recognition and courtship. While the larval are capable of only limited movement. #17 Life Cycle & Natural History of stages of both are aquatic, the eggs, pupae, Aquatic Insects (Part 5) However, Megaloptera pupae are quite and adults are all terrestrial. #18 Life Cycle & Natural History of mobile and can defend themselves within Aquatic Insects (Part 6) Elongated eggs are deposited in the pupal chamber. Adults emerge after #19 Life Cycle & Natural History of masses on vegetation overhanging the about two weeks. The process from egg- Aquatic Insects (Part 7) water, large rocks projecting from the laying to adult emergence may take one to water, or manmade structures, like bridge two years for sialids, and up to five years Collect this entire educational series abutments. The eggs hatch at night for some corydalids. for future reference! Contact us at and, after 5 to10 days, the first instars 1-800-781-1989 if you’d like a copy Adults are relatively short-lived, of previous Fact Sheets or a binder drop into the water. Sialids appear to with a lifespan of just a few days. Once for storing them. be photopositive, swimming toward the emerged, some are active at night while others are active during the day. Sialids do not readily fly and remain close to where they emerge. Corydalids are active fliers. They may fly some distance from the water and are generally attracted to lights. With such short lifespans, adults mate quickly and die. The aquatic larva of a sialid species collected Habitat from LaBarque Creek. orydalids are typically found in well- (Photo by Darlene Haun, Coxygenated streams and lakes, but Missouri Department of can also be found in productive ponds Conservation.) or swamps where dissolved oxygen may (continued on back) Stream Team Academy Fact Sheet #19 be low. Sialids are generally found in may be simple or segmented and, in the same habitats, but require mud or certain corydalids, are supplemented silt deposits and accumulated detritus with tufts of tracheal gills to increase the for burrowing. Although they are large surface area for oxygen transfer. Some invertebrates, several species can survive corydalids also have functioning posterior in intermittent streams by burrowing into spiracles which enable them to breathe the substrate during dry periods. Sialids when they leave the water to pupate or are generally classified as burrowers, while when dissolved oxygen is low. corydalids are classified as clingers or climbers. Conclusion Megaloptera larvae can be good Feeding indicators of water quality. Corydalid egaloptera larvae are predacious species tend to be sensitive to changes Mfrom the time they hatch until they in dissolved oxygen while sialids can be pupate. They are indiscriminate, active somewhat tolerant of low oxygen levels. predators, feeding on aquatic insects, However, the species of both families annelids, crustaceans, and mollusks. play an important role as predators in the Because the digestive tract of adults is aquatic systems where they are found. reduced in size, they feed only on liquids. Megaloptera is one of our most interesting insect orders. They are the Respiration only aquatic insect group that is aquatic egaloptera larvae can be during only the larval stage, while the distinguished from most beetle M remaining life stages are terrestrial. larvae fairly easily by their paired lateral The name means “large wing” and they abdominal gill filaments. These filaments are known for their clumsy flight. The males are also intimidating with their large tusks or pinchers. In the aquatic macroinvertebrate world, these are our charismatic megafauna.

A ventral view of a hellgrammite. Note the An adult male dobsonfly displaying large tusks. large mandibles and tracheal gill tufts. (Photo by John Abbott, University of Texas.) (Photo courtesy of Jason Neuswanger, Troutnut.com.)

Our next fact sheet will cover midges, mosquitoes, aquatic gnats, and flies (Diptera). Don’t forget to send your questions to [email protected] or call 1-800-781-1989. Sources:

Freshwater Macroinvertebrates of Northeastern North America. Barbara L. Peckarsky et al. 1990.

Aquatic Entomology–the Fishermen’s and Ecologists’ Illustrated Guide to Insects and Their Relatives. W. Patrick McCafferty. 1998.