Aquatic Insects of Michigan

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

Aquatic and Semiaquatic Heteroptera of Michigan - True Bugs - Identification

Introduction

True bugs, or the Heteroptera, have in the past been frequently grouped with the Homoptera (cicadas, treehoppers, planthoppers, whiteflies, aphids, scales) in Hemiptera (i.e., Heteroptera+Homoptera). Both groups are similar in mouth part construction, but differ in beak placement and wing structure (Heteroptera: 1) piercing-sucking mouthparts with a segmented rostrum, or beak, arising from the front of the head; 2) in winged-forms, a scleritized basal 2/3 wing, and a distally membranous 1/3 wing; Homoptera: 1) mouthparts arising from the posterior portion of the head; 2) wings uniformly sclerotized or thickened).

There are over 3000 species worldwide of aquatic and semiaquatic heteropterans, and approximately 70 genera and over 400 species in North America. Only 6 families of Heteroptera in Michigan are truly aquatic, and these are characterized by having reduced or hidden antennae. Of the 11 semi-aquatic families in North America, 7 are found in Michigan. There are not many truly aquatic species, but many species interface somehow with aquatic environments. In fact, true bugs occupy diverse aquatic environments - saline ponds, high mountain lakes, hot springs, and large rivers.

Heteropterans are basically predators, and many have developed defenses against predation, attributed to heteropteran scent glands. Only corixids differ, and many are collector-gatheres and are heavily preyed upon.

Adults (adapted from Polhemus 1996)

1a	a. Antennae shorter than head, inserted beneath eyes, not plainly visible from above	2
	also: Aquatic or semiaquatic, at margins of lotic or lentic habitats
1b	a. Antennae longer than head, inserted forward of eyes, plainly visible from above	7
	also: Semiaquatic, on surface (nektonic) or at aquatic margins
2a(1a)	a. Beak triangular, very short, unsegmented but often transversely striated, appearing as apex of head	Corixidae
	b. Front tarsus with a single segment, scooplike, fringed with stiff setae forming a rake
2b	a. Beak cylindrical, short to long, with 3 or 4 segments	3
	b. Front tarsus not scooplike or fringed with stiff setae
3a(2b)	Apex of abdomen with a pair of flat, retractile air straps with pubescence on the surface	Belostomatidae
3b	Apex of abdomen terminating in a long, single cylindrical siphon composed of 2 slender, nonrectractile filaments	Nepidae
3c	Apex of abdomen without respiratory appendages	4
4a(3c)	a. Middle and hind legs without fringe-like swimming hairs	Gelastocoridae, Gelastocoris oculatus (Fabricius)
	b. Ocelli present
	also: Front legs raptorial (grasping), femora broad; rostrum short, not reaching the hind coxae; antennae not visible from above; toad-like in appearance
4b	a. Middle and hind legs with fringe-like swimming hairs	5
	b. Ocelli absent
	also: aquatic; not toad-like in appearance
5a(4a)	a. Front legs raptorial, femora broad	Naucoridae, Pelocoris femoratus (Palisot de Beauvois)
	b. Body dorsoventrally flattened
5b	a. Front legs slender, femora not broad	6
	b. Body strongly convex dorsally
6a(4b)	a. Body form ovoid, very small (length < 3mm)	Pleidae, Neoplea striola (Fieber)
	b. All legs similar
	c. Hind tarsus with 2 well-developed claws
6b	a. Body form elongate, length 5 mm or more	Notonectidae
	b. Hind legs long, oarlike
	c. Claws of hind tarsus inconspicuous
7a(1b)	a. Membrane of wing with 4 or 5 distinct similar cells	Saldidae
	b. Hind coxae large, transverse, with broad coxal cavity
7b	a. Membrane of wing without distinct similar cells	8
	b. Hind coxae small, cylindrical, or conical, with coxal cavity socketlike
8a(7b)	Claws of at least front tarsus inserted before apex of leg	9
8b	Claws of all legs inserted at tips of tarsus	10
9a(8a)	a. Hind femur short, distally either scarcely or not surpassing apex of abdomen	Veliidae
	b. Metasternum with a pair of lateral scent grooves terminating on pleura in front of hind coxae
	c. Dorsum of head usually with a medial longitudinal sulcus or glabrous (smooth) stripe
	d. Middle legs inserted about midway between front and hind legs (except Rhagovelia, which has a feathery-like structure on the middle tarsus)
9b	a. Hind femur long, distally greatly exceeding apex of abdomen (except scarcely exceeding apex in Rheumatobates females)	Gerridae
	b. Metasternal region with a single median scent gland opening (omphalium)
	c. Dorsum of head without a median groove or line (except in Rheumatobates)
	d. Middle legs inserted closer to hind legs than fore legs
10a(8b)	a. Body long, slender, stick-like	Hydrometridae, Hydrometra martini Kirkaldy
	b. Head as long as, or longer, than combined length of pronotum and scutellum
10b	a. Body stout, not stick-like	11
	b. Head not greater than combined length of pronotum and scutellum, or pronotum alone in wingless form
11a(10b)	a. Tarsi 2-segmented	Hebridae
	b. Head ventrally with a deep, longitudinal channel for reception of rostrum
11b	a. Tarsi 3-segmented	Mesoveliidae
	b. Head ventrally without a longitudinal channel
	also: Inner margins of eyes converging anteriorly; femora with at least 1 or 2 black spines on dorsum distally; winged forms with exposed bilobed scutellum

References

Polhemus JT. 1996. Aquatic and Semiaquatic Hemiptera, pp. 267-297 in Merritt RW, Cummins KW (eds.), An Introduction to the Aquatic Insects of North America, Third Edition. Dubuque, Iowa: Kendall/Hunt Publishing Company.

Page created: July 25, 2003; Last edited: November 06, 2013 (EB)