Aquatic Insects of Michigan

by Ethan Bright, Museum of Zoology Insect Division and School of Natural Resources and Environment
University of Michigan

Megaloptera (Dobsonflies, Fishflies, and Alderflies) of Michigan - Identification

Introduction

[under construction]

Adults
(adapted from Evans and Neunzig 1996, Davis 1903, Arnold and Drew 1987)

1a	a. Less than 25mm in length (most 10-15mm)	Sialidae, Sialis Latreille
	b. Ocelli absent
	c. 4th tarsal segment dilated
1b	a. Over 25mm in length	Corydalidae, 2
	b. Ocelli present
	c. 4th tarsal segment like preceding segments, not dilated
2a(1b)	a. Fore wing with white spots in many cells	Corydulus cornutus (Linneaus)
	b. 20 veins or more reaching wing margin posteriad of R1
	c. M vein with 3 branches reaching wing margin
	also: Males with dramatic and very large, pincer-like mandibles
Fig. x
2b	a. Fore wing lacking white spots or, if present, spots less widely distributed	3
	b. Fewer than 20 veins reaching wing margin posteriad of R1
	c. M vein with 2 branches reaching wing margin
3a(2b)	M vein of hind wing with 3 branches reaching wing margin	Neohermes concolor (Davis)
	also: Fore wing with crossvein between R3 and R4; male antenna elongate, moniliform (beadlike), setigerous (bearing setae); apical papilla of gonapophysis lateralis in female absent
3b	M vein of hind wing with 2 branches reaching hind wing margin	4
4a(3b)	a. Wings dark with large white spots or patches	Nigronia Banks, 5
	b. Posterior costal cells of fore wing about as long as broad
	c. Fork of A2 well beyond crossvein between A1 and A2
	Habitat: Lotic, usually cold- and cool-water streams
4b	a. Wings pale gray-brown, mottled	Chauliodes Latreille, 6
	b. Posterior costal cells of fore wing distinctly longer than wide
	c. Crossvein between A1 and A2 at or beyond fork of A2
	Habitat: Lentic, usually warm-water ponds, wetlands and still backwater areas of streams and rivers
5a(4a)	a. Continuous, broad, somewhat arcuate white band extending across the middle of each wing through the anal region of each	Nigronia fasciatus (Walker)
	b. Antennae serrate in female, flabellate in male
5b	a. Irregular band of white spots, generally broadest in front, extending across the middle of each front wing, on the hind wing represented by only a few minute dots which may be wanting; in both wings, anal region is black	Nigronia serricornis (Say)
	b. Antennae serrate in both sexes
6a(4b)	a. Male antennae pectinate, female antennae serrate	Chauliodes rastricornisRambur
	b. Vertex of head with two large, rectangular, dark brown spots posterior to the ocelli
	c. In lateral view, male anal plate triangular
6b	a. Antennae in both sexes pectinate	Chauliodes pectinicornis (Linneaus)
	b. Vertex of head with large, rectangular, yellow spots
	c. In lateral view, male anal plate cylindrical

Pupae
(adapted from Evans and Neunzig 1996)

1a	a. Length ca. 10-12 mm	Sialidae, Sialis Latreille
1b	a. Length > 29 mm	Corydalidae

Larvae
(adapted from Cuyler 1958, Evans and Neunzig 1996, Neuzig 1966)

1a	a. Length of mature larvae 25 mm or less	Sialidae, Sialis Latreille
	b. 7 pairs of 4-5 segmented lateral filaments on Ab1-7
	c. Posterior end of abdomen with a single long caudal filament
1b	a. Length of mature larvae 30 mm or more	Corydalidae, 2
	b. 8 pairs of 2-segmented lateral filaments on Ab1-8, and pair of 1-segmented filaments on Ab10
	c. Posterior end of abdomen with 2 anal prolegs, each bearing a pair of claws (prolegs)
2a(1b)	a. Ab1-7 with ventral gill tufts at the base of each lateral filament	Corydulus cornutus (Linneaus)
	b. Lateral margins of gena strongly angulate
	c. Antennae 5-segmented
	d. Abdominal club hairs present
2b	a. Ab1-7 without gill tufts	3
	b. Lateral margins of genae convex or weakly angulate
	c. Antennae 4-segmented
	d. Abdominal club hairs absent
3a(2b)	Larval head conspicuously patterned	Neohermes concolor (Davis)
	also: Spiracles on Ab8 distinct, associated with raised areas of the integument
3b	Larval head not conspicuously patterned	4
4a(3b)	a. Ab8 with spiracles at the ends of two long respiratory tubes extending past the prolegs	Chauliodes Latreille, 5
4b	a. Ab8 with spiracles at the ends of two short, tapered respiratory tubes, about 1.5x long as wide	Nigronia Banks, 6
5a(4a)	a. Middorsal stripe of abdomen black	Chauliodes rastricornisRambur
	b. Length of the longer respiratory tube as long as combined middorsal lengths of Ab6-8 or Ab5-8
5b	a. Middorsal stripe of abdomen yellowish	Chauliodes pectinicornis (Linneaus)
	b. Length of the longer respiratory tube as long as combined middorsal lengths of Ab7-8
6a(4b)	a. Respiratory tube about 3x long as wide, longer than the middorsal length of its abdominal segment	Nigronia fasciatus (Walker)
	b. Bases of respiratory tubes close together, nearly contiguous
6b	a. Respiratory tubes shorter, about 1.5x long as wide, and shorter than the middorsal length of its abdominal segment	Nigronia serricornis (Say)
	b. Bases of respiratory tubes widely separated

References

Arnold DC. Drew WA. 1987. A preliminary survey of the Megaloptera of Oklahoma. Proceedings of the Oklahoma Academy of Science 67:23-26.
Davis KC. 1903. Sialididae of North and South America, pp. 442-486 in Felt EP, Aquatic Insects in New York State. New York State Museum 68(Entomoloy 18). 517p + 52 plates.
Evans ED, Neunzig HH. 1996. Megaloptera and Aquatic Neuroptera, pp. 298-308 in Merritt RW, Cummins KW (editors), An Introduction to the Aquatic Insects of North America, 3rd Edition. Kendall/Hunt Publishing Company: Dubuque, Iowa. 862 + xiii p.

Page created: August 28, 2003; Last edited: November 10, 2013 (EB)