Lackawanna River Corridor Association

Lackawanna River Watch Report Macroinvertebrate Collections 1991-98

Lackawanna River Corridor Association
2006 N. Main Ave.
Scranton PA 18501-0368
Phone: (570) 207-7608
Fax: (570) 207-7590
Email: lrca@epix.net

Last Update: 10/30/2003

Copyright © 2003
Lackawanna River Corridor Association

Macroinvertebrates are the aquatic organisms living along the bottoms of rivers, streams, lakes and wetlands that do not have a backbone and that you can see with the naked eye. They range in size from nearly microscopic midges and black flies to large hellgrammites and crayfish. Most aquatic macroinvertebrates are insects, however snails, clams, and crayfish are also common. All have their own adaptations and requirements to life under water, making some more sensitive to water pollution than others. This makes macroinvertebrates good indicators of water quality. One group of organisms especially sensitive to water pollution are the EPT's: the combined insect Orders of Ephemeroptera (mayflies), Plecoptera (stoneflies) and Trichoptera (caddisflies). High numbers of EPT organisms in a stream represents good water quality. Their absence or just occasional occurrence may indicate a pollution problem. A macroinvertebrate community dominated by organisms more tolerant of pollution, such as aquatic worms and midges, usually indicates a problem.
The following is a simplified key to identify macroinvertebrates found in the Lackawanna River and its tributaries. A brief description, an indication of its pollution sensitivity and distribution in the River, and pictures of individual organisms are included in each of the links in this key. Descriptions and distributions of the macroinvertebrates discussed here reflect observations made by LRCA staff and volunteers, based on data collected over the past ten years. The organisms pictured here do not reflect a complete list of every macroinvertebrate found in the River.

1a. Organism has a shell(s) Snails, Limpets & Clams

1b. Organism has no shell go to 2a

2a. Body with no legs go to 3a

2b. Body with legs go to 4a

3a. Worm-like Aquatic Worms & Leeches

3b. With tentacles, brushes or tails Craneflies, midges, blackflies & other

4a. Four pairs of legs Water Mite

4b. Ten or more legs Crayfish, Scuds, Sowbugs

4c. Three pairs of legs go to 5a

5a. Beetle-like Riffle Beetles

5b. Not beetle-like go to 6a

6a. Three tails Mayflies

6b. One or two tails go to 7a

6c. No obvious tails go to 8a

7a. Two long and stiff tails Stoneflies

7b. Body with side appendages; one or two tailed Dobsonflies, Alderflies, Fishflies

8a. Green, tan, orange, or white body; may live in stone or stick case Caddisflies

8b. Alternating brown and black bands; nearly microscopic Beetle larvae

8c. Body thick, some with side appendages, brown, larger than above More beetle larvae

8d. Big black or brown body, large eyes Dragonflies

8e. Brown body; flat and round, looks like a penny Water Penny

8f. White body with three pairs of legs at front and prolegs at back Pyrallid Caterpillar

1a. Organism has a shell(s)	Snails, Limpets & Clams
1b. Organism has no shell	go to 2a
2a. Body with no legs	go to 3a
2b. Body with legs	go to 4a
3a. Worm-like	Aquatic Worms & Leeches
3b. With tentacles, brushes or tails	Craneflies, midges, blackflies & other
4a. Four pairs of legs	Water Mite
4b. Ten or more legs	Crayfish, Scuds, Sowbugs
4c. Three pairs of legs	go to 5a
5a. Beetle-like	Riffle Beetles
5b. Not beetle-like	go to 6a
6a. Three tails	Mayflies
6b. One or two tails	go to 7a
6c. No obvious tails	go to 8a
7a. Two long and stiff tails	Stoneflies
7b. Body with side appendages; one or two tailed	Dobsonflies, Alderflies, Fishflies
8a. Green, tan, orange, or white body; may live in stone or stick case	Caddisflies
8b. Alternating brown and black bands; nearly microscopic	Beetle larvae
8c. Body thick, some with side appendages, brown, larger than above	More beetle larvae
8d. Big black or brown body, large eyes	Dragonflies
8e. Brown body; flat and round, looks like a penny	Water Penny
8f. White body with three pairs of legs at front and prolegs at back	Pyrallid Caterpillar