Aquatic Macroinvertebrate ID Resources and skills necessary for good invertebrate ID: 1. Solid introduction - Preferably a general or aquatic entomology class, or other training from a reputable source. 2. Good references - for family level ID s: Bouchard, R.W. 2004. Guide to Aquatic Invertebrates of the Upper Midwest. Water Resources Center, University of Minnesota. St. Paul, MN. (www.vsmp.org) Voshell, J.R. 2002. A Guide to Common Freshwater Invertebrates of North America. McDonald & Woodward Publishing Co. McCafferty, W.P. 1998. Aquatic Entomology. Jones & Bartlett Publ.
Resources and skills, con t 3. Proficiency with keys Caveat #1: Picture matching is dangerous! Good for verification, but not for identification. You must confirm your ID with the key or salient characteristics of taxa in question. Caveat #2: ID keys are written by people who know what they are looking at. Everything is relative! The decisions you need to make are usually based on either presence/absence of a character, or some relative or proportional difference.
Resources and skills, con t Caveat #3: Keys are developed using specimens that are mature (final instars) and intact. instar an immature insect between molts. Tips: - Keys are structured to allow backtracking. Ex. 2(1), 3(1 ), 10(3, 8). - When multiple characters are given in a couplet, they are listed in order of decreasing reliability.
Resources and skills, con t The Solution? Practice, Practice, Practice! - Collect and observe on your own, participate in Stream Searches / Round Up s and Bug ID Days, or help build a reference collection for your group. - Gestalt ID comes with experience.
Mouthparts Four parts used for ID: 1. labrum (upper lip) 2. mandibles 3. maxillae 4. labium (lower lip)
Labrum Philopotamid caddisfly larva with t-shaped labrum.
Mandibles Hydrophilid beetle larva with large mandibles (and larger maxillae).
Maxillae
Labium
Damselfly nymph with labium fully extended.
Rostrum, or beak, of a generalized hemipteran showing modifications to mouthparts (piercing/sucking).
Lateral (above left) and ventral (below left) views of the head of a caddisfly larva. Note the opening of the silk gland at the tip of the labium. The maxillae and labium of larval Trichoptera and Lepidoptera are blunted and stubbier in appearance than in the other orders of aquatic insects.
Ventral view of the larval head capsules of a tipulid (left) and an athericid (right). The Diptera are divided into two groups, Nematocera and Brachycera. Larvae of the Nematocera have mouthparts like those of the tipulid larva (mandibles moving against each other in a horizontal plane), while those of the Brachycera have mouthparts like the athericid (mandibles moving vertically and parallel to each other).
Legs Six classical segments: 1. Coxa (coxae) 2. Trochanter 3. Femur (femora) 4. Tibia (tibiae) 5. Tarsus (tarsi) 6. Tarsal claw(s)
Coxa (coxae)
Trochanter
Femur (femora)
Tibia (tibiae)
Tarsus (tarsi) -3 tarsal segments in this example.
Tarsal claw(s)
a b c d e Some examples of the wide variety of gill structures found in mayfly nymphs. Simple lamellate gills (a); lamellate gills with tufts (b); forked gills (c); operculate gills (d and e). a, c, d from Merritt and Cummins, 1996; b,e from Peckarsky, et al 1990.
d Th b Ab a c e Some examples of gill placement in stonefly nymphs. Thoracic (Th) and abdominal (Ab) gills (a); cervical gills (b); submental gills (c); coxal gills (d,); subanal lobe gills (e). Ventral views of head (b,c), mesothorax (d), abdomen (e), and head through first two abdominal segments (a). a, b, c from Merritt and Cummins, 1996; d from Stewart and Stark, 1988; e from Peckarsky, et al 1990.
References Bouchard, R.W. 2004. Guide to Aquatic Invertebrates of the Upper Midwest: identification manual for students, citizen monitors, and aquatic resource professionals. Water Resources Center, University of Minnesota. St. Paul, MN. 208pp. www.vsmp.org. McCafferty, W.P. 1998. Aquatic Entomology: the fishermen s and ecologist s illustrated guide to insects and their relatives. Jones & Bartlett Publ. Sudbury, MA. 448pp. Merritt, R.W.,K.W. Cummins and M.B. Berg (eds.). 2008. An Introduction to the Aquatic Insects of North America. 4th ed. Kendall/Hunt Publ. Co. Dubuque, Iowa. 1158pp. Peckarsky, B.L., P.R. Fraissinet, M.A. Penton, and D.J. Conklin, Jr. 1990. Freshwater Macroinvertebrates of Northeastern North America. Cornell Univ. Press. Ithaca, New York. 442pp. Stewart, K.W. and B.P. Stark. 2002. Nymphs of North American Stonefly Genera (Plecoptera). 2nd ed. The Caddis Press. Columbus, Ohio. 522pp. Voshell, J.R. 2002. A Guide to Common Freshwater Invertebrates of North America. McDonald & Woodward Publishing Co. Blacksburg, VA. 456pp. Wiggins, G.B. 1998. Larvae of the North American Caddisfly Genera (Trichoptera). 2nd ed. Univ. of Toronto Press. Toronto, Canada. 457pp.