Aquatic Insects of Michigan
Ethan Bright, Museum of Zoology Insect Division and School of Natural
Resources and Environment
Megaloptera of Michigan
This small holometabolous order has just two families, Corydalidae (Dobsonflies, Fishflies) and Sialidae (Alderflies), both of which occur in Michigan. There are normally 10-11 larval instars, and life cycles of most species are 1-3 years, with emergence in late spring or early summer. Larvae of all species are carnivorous; little is known about the feeding habits of our short-lived adults.
The larvae of Corydalyidae are known as hellgrammites. Eggs are laid terrestrially, proximate to water, and hatch rapidly 3-5 days after laying, with first instar larvae dropping into the water. Larvae are predacious, feeding principally on mayflies, dragon- and damselflies, caddisflies and dipterans. After growth of 2-5 years, larvae leave the water for a distance of 20-35 cm (but can be considerably farther) to a log or moist terrestrial environment to construct a pupal chamber. Adults are short-lived, generally poor fliers, emerge at night and fly into trees to locate each other and mate. Adults are photophilous, and are often collected in light traps and ordinary street or house lights. Males have large mandibles, obstensively for courtship purposes.
Alderfly larvae generally inhabit depositional silt in lentic and lotic environments. Life history is very similar to Corydalidae: females oviposit eggs terrestrially, often in large numbers on vegetation proximate to water. Eggs hatch rapidly 3-5 days after laying, with the first instar larvae dropping into the water. Larvae are predacious, feeding principally on small mayflies and midges. Larvae are both lentic and lotic, usually burrowing into depositional areas of silt. Common in littoral zones of some lakes, but also can be found further out from shore.There are 10 larval instars requiring 1-2 years to reach the terminal larval instar. Pupation is terrestrial, and adults do not feed. Adults are short-lived and are generally poor fliers. Adults are not photophilous; larvae and adults lack ocelli. One must either collect them on the wing or among nearby vegetation. Sialid larvae are distinct from corydalids in that the last abdominal segment does not have anal claws, but rather has a long, slender median terminal filament.
The following list is based on specimens deposited at the UMMZ-Insect Division and Cook Collection (Michigan State University). [Picture above of Chauloides rasticornis courtesy of Linda Benoche, Ann Arbor, Michigan].
Corydalidae - Dobsonflies and Fishflies
Five species in four genera are recorded from Michigan, with one additional species possibly to be encountered in the state based on existing regional distributional records. Neohermes concolor is known in Michigan only from several blacklight-collected specimens from the extreme sw part of the Lower Peninsula. Michigan specimens of Nigronia fasciatus in the UMMZ-Insect Division were determined by the author to be misidentified N. serricornis. However, based on this species known distribution, it may occur in the southern part of the Lower Peninsula.
Sialidae - Alderflies
10 species in one genus are recorded from Michigan. The following list based on Ross (1938) and specimens in the UMMZ-Insect Division collection. Note: species denoted in bold-blue have been recorded in Michigan, other are likely to be found in the state based on existed regional distribution records.
created: November 01, 2002 - Last updated :
July 21, 2011
: July 21, 2011 (EB)