Sub-phylum Crustacea (Crayfish, Shrimp, Scuds and Sowbugs) 
Courtesy of the Cacapon InstituteMore than three pairs of legs (> 6) attached to the thorax; the first several pairs of legs may have a hinged claw, which is often enlarged as in the order Decapoda; bodies strongly flattened from top to bottom or from side to side; abdomen consists of individual segments or the segments may be fused to form a thoracic shield; some kinds have a broad flipper on the end of the abdomen. 

Order Amphipoda


Gammaridae (Sideswimmer): Has a shrimp-like appearance; body flattened from side to side; one pairs of antennae of equal length; seven-pairs of walking legs, first two are claw-like the remaining legs are simple.  Has a habit of swimming sideways. Crawler/burrower; Collector/gatherer; S-M (M)(F)

Order Decapoda


Cambaridae (Crayfish): Body mostly dorsally flattened; two-pairs of antennae one longer than the other; five-pairs of legs, first three-pairs with hinged claws and the first pair of claws are greatly enlarged; abdomen terminates in a flipper-like structure. Crawler/burrower; Collector/gatherer; M-VL (M)(S/F)


Palaemonidae (Freshwater shrimp): Cephalothorax and abdomen cylindrical with some side-to-side flattening; 5-pairs of walking legs the first two have claws, which are not enlarged; abdomen terminates in a flipper-like structure. Crawler/swimmer; Scraper; M-VL (M)(S)

Order Isopoda


Asellidae (Aquatic sowbug): Body dorsally flattened; two-pairs of antennae one longer than the other; seven-pairs of legs, the first is claw-like and slightly enlarged, and the others have a simple pointed claw.  Looks similar in appearance to its terrestrial cousin. Crawler/burrower; Collector/gatherer; S-M (H)(S/F)

Note: Crustaceans listed below are occationally collected, but due to their very small sizes and unknown tolerances are not usually included in biosurvey analysis. 
5.  Sub-order Cladocera (Water flees): Body is usually round or oval shaped appearing to consists of two valves as in a clam; large eyes on the head. Collector/Filterer (< 3 mm) 
6. Sub-class Copepoda (Copepods): Body is cylindrical having a single eye; abdomen and some thoracic segments form a tail-like structure. Collector/Gatherer/Filterer (< 4 mm) 
7.  Class Ostracoda (Seed Shrimp): Body is covered by a shell giving the organism a bivalve-like appearance. Most of the animal is covered but some of its appendages may protrude. Collector/Gatherer/Filterer (< 3 mm)