Aquatic Insects of Michigan

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

Halipidae (Crawling Water Beetles) of Michigan

There are 19 species in 3 genera recorded in Michigan, with another 6 species of Haliplus and 1 species of Peltodytes likely to be recorded based on these species known distribution. One species, Brychius hungerfordi, is one of two aquatic insect species found in Michigan on the endangered species list (the other is the corduliid dragonfly Somatochlora hineana), and is known from only several disjunct populations in Michigan and the Bruce Peninsula in Ontario (Strand & Spangler 1994). It is found in cold-water dominated streams in riffle habitats. Haliplus and Peltodytes are commonly encountered among macrophytes of lakes, ponds and margins of slow-moving lotic systems. Mostly herbivorous, larvae undergo three instars, and pupate under a stone or log along aquatic margins. Adults are also mostly herbivorous, and may overwinter in the habitats were egg-laying takes place (Hilsenhoff & Brigham 1978).

Larvae
(adapted from White and Roughley 2008)

1a	a. Body semgnets each with 2 or more erect, segmented, hollow, spine-tipped filaments, each filament half as long as the body	Peltodytes Regimbart
	b. Forelegs chelate, 4th segment produced apically and edged with a solid row of small teeth so that the 5th segment and claw can be closed on it
1b	a. Body spines, except in 1st instar, ever stalked or much longer than the length of the 1st body segment	2
	b. Forelegs, if chelate, with 4th segment less produced and without a solid row of small teeth
2a(1b)	a. Ant3 shorter than Ant2	Brychius hungerfordi Spangler
	b. Forelegs moderately chelate, but 3rd instead of 4th segment produced, edged with 2 blunt teeth
	c. Last abdominal segment unforked, strongly curved ventrally
	d. Body without conspicuous spines
	also: very rare, known only from a few populations in cold-water lotic streams
2b	a. Ant3 2-3x as long as Ant2	Haliplus Latreille
	b. Foreleg weakly to moderately chelate, usually bearing 2-3 spines
	c. Last abdominal segment not strongly curved ventrally
	d. Body with or without conspicuous spines
	also: very common, mostly lentic

Adults
(adapted from White and Roughley 2008)

1a	a. Pronotum rounded, with distinct black notch on each side of the middle near the posterior margin	Peltodytes Regimbart
	b. Last segment of both labial and maxillary palpi cone-shaped, as long or longer than the next to last segment
	c. Hind coxal plates large, only last abdominal sternite completely exposed
	d. Elytron with fine sutural stria in at least the apical half
1b	a. Pronotum immaculate, or with an anterior median blotch, or both or with 2 indistinct blotches	2
	b. Last segment of both labial and maxillary palpi sublate, shorter than the next to last segment
	c. Hind coxal plates smaller, leaving the last 3 abdominal sternites exposed
	d. Elytron without fine sutural stria
2a(1b)	a. Pronotum with sides of basal two-thirds nearly parallel	Brychius hungerfordi Spangler
	b. Epipleuron broad, extending almost to the tip of the elytron, which is never truncate
	c. Metasternum reaching epipleuron
2b	a. Pronotum with sides widest at base, convergent anteriorly	Haliplus Latreille
	b. Epipleuron evenly narrowed, usually ending near base of the last abdominal sternite, never reaching the elytral apex
	c. Metasternum separated from epipleuron by the episternum