The common name scud has a Scandinavian origin and refers to the movement of these animals. In Norwegian, skudda means to push. This was adopted in English as scud and came to mean to move or run swiftly. Anyone who tries to catch one of these organisms swimming in a pan of water will understand how well this common name applies. Sideswimmer refers to the way that they swim. The scientific name for this order comes from two Greek words: amphi, meaning of both kinds and pod, meaning foot. This name refers to the two kinds of appendages on the bottom of the body, as seen in side view. Long walking legs protrude down on approximately the front half of the body, while much shorter and simpler swimming appendages protrude down on the rear half of the body.
In many of the fly fishing waters, scuds are an important high-protein food source for trout. Yet most anglers focus on more "normal" foods, such midges, mayflies, and damselflies. Perhaps that's because scuds are hard to classify. They are not an aquatic insect, nor are they a terrestrial. In fact they are not an insect at all.
Most of the species of scuds that are likely to be collected in surface waters belong to three families: Hyallelidae, Grammaridae, and Crangonyctidae. The most important family to he fisherman is the Grammaridae.
No matter what you call them scuds, side swimmers or freshwater shrimp (calling them a shrimp is a misconception), you should always have a few of them in your box.
The body is strongly flattened from side to side. The body segments are grouped into three regions: cephalothorax; thorax; and abdomen. The cephalothorax is a combination of the head and first thorax segment. The thorax is composed of the next seven segments after the cephhalothorax. The abdomen consists of the six individual segments to the rear of the thorax. There are two pairs of antennae on the cephalothorax about the same size. The thorax has seven pairs of walking legs, one pair per segment. The first pair of walking legs has large hinged claws for grasping. The remaining five pairs of walking legs have a simple point on the end. There are six pairs of short appendages on the underside of the abdomen, one pair per segment. The color of most live organisms is a creamy light gray or brown, and they are somewhat translucent. Some kinds have brilliant colors, including green, blue, purple, lavender, or red. The same species is often different colors in different locations. Unfortunately, the colors of all kinds of scuds fade to dull white, cream, or gray when preserved.
The body length of scuds ranges from 5 mm to 20 mm, without the antennae and tails.
Scuds live in many types of habitats, including riffles; slow water that does not allow particles to be suspended; subterranean; and, in lakes from a point on shore to where the light penetration ends. They are most common in the shallows of cool streams, springs, seeps, lakes, and ponds. They live in all sizes of habitats, but they are often most abundant in very small habitats that do not have fish populations. Scuds sometimes occur in the backwaters of large rivers. Generally, scuds do not inhabit temporary habitats, but sometimes they live in pools left on the flood plain after high water has receded. A few kinds live in very hot springs. They are rarely in water deeper than one meter. Scuds are bottom dwellers, primarily in small spaces within tangles of live aquatic plants, roots, coarse detritus, or stones. Sometimes they reside in the upper layer of soft sediment.
Aquatic sow bugs, which are also called Isopoda, are one of the subphylum Crustacea. There are about 130 species of freshwater isopods in North America. This represents only about 5% of the total number of species, because most isopods are marine or terrestrials. Practically all of the species of aquatic sow bugs that live freely in surface waters throughout most of the continent are in one family, Asellidae. There are three other families with a few species, but these are seldom encountered because they have very specialized lifestyles or narrowly restricted distributions.
|The body is flattened from top to bottom.|
|Body segments are grouped into three parts: cephalothorax, thorax, and abdomen.|
|Cephalothorax is a combination of the head and first thorax.|
|Thorax is composed of the next seven segments.|
|Abdomen consists of all segments to the rear of the thorax, fused into a short, broad, shield-like region.|
|One pair of antennae is much longer than the other pair.|
|Seven pairs of long walking legs are present on the thorax, one pair per segment.|
|First pair of walking legs has hinged claws for grasping.|
|Next six pairs of walking legs grow longer and each has a sharp claw on the end.|
|All thorax segments have a shelf-like projection on each side that covers the base of the legs.|
|The first five pairs of appendages are hidden under the abdomen in top view.|
|Most are gray in color, but a few are black and brownish colored.|
Size: When mature sowbugs measure from 5 to 20 mm.
Sowbugs can be found in many different types of water. They are found in shallow water, rarely found in places that are deeper than one meter. They can be found in seeps, springs, and small spring-fed streams. If the substrate has a lot of hiding places, they can be abundant. A few kinds live in the margins of lakes.
Sowbugs breed throughout the year, but in waters that are subject to temperature change breed in the spring. Each sowbug molts up to 15 times and have a life cycle that last about one year. See Scuds for more information about fishing techniques. Although there are several families of sowbugs, the Asellidae is by far the most important to fisherman.
Crayfish live in streams, rivers, swamps, ponds, and other freshwater habitats. Most crayfish are strictly aquatic but some live in semi-aquatic environments. The semi-aquatic crayfish burrow into the soil to get to water (so that they can breathe).
This crustacean has a hard exoskeleton that protects and supports the body. The crayfish has 8 jointed walking legs, a segmented body, 2 pairs of sensory antennae, and compound eyes. It has 2 large pincers or claws called chelipeds. If a crayfish loses a leg, the leg will regenerate (regrow). The head and thorax are fused, forming the cephalothorax. Using gills, a crayfish breathes oxygen that is dissolved in water. Juvenile crawfish are light tan, but adults are deep red. Their color also depends on diet. As a crayfish grows, it often molts (loses its old shell and grows a new one). It eats the old shell.
Crawfish in North America range from 2 to 6 inches (5-15 cm) long; Australian crawfish are larger.
Crayfish occur in a wide variety of shallow freshwater, and some live in swamps and wetlands. They are benthic and, at least in daylight hours, usually remain hidden in burrows or under stones and debris.
Crayfish are found along the bottom of the stream so patterns must be weighted and fished deep. When disturbed, crayfish will retreat rapidly backwards. Most patterns are tied with the head at the bend of the hook. When fishing the Eleven Point River in Missouri, a crayfish is the go-to pattern.