Medium Browns and Yellows

This family contains some very important species inhabiting most freestone streams across the continent. They are often mistaken for early instar (Instar: Many invertebrates molt through dozens of progressively larger and better-developed stages as they grow. Each of these stages is known as an instar. Hard-bodied nymphs typically molt through more instars than soft-bodied larvae.) Perlidae (Golden Stones), which they closely resemble. The most notable differences between the two families are the perlodids much longer tails and antennae and usually more slender appearance. Their lack of obvious thoracic (Thorax: The thorax is the middle part of an insect's body, in between the abdomen and the head, and to which the legs and wings are attached.) gilling is another difference. The most important genus of the family, Isoperla, is the easiest to recognize with its longitudinally striped abdomens (though this is not a hard fast rule).

The family can be broken down into two groups:

The subfamily Isoperlinae, or Stripetails - contains five genera; three are monotypic (Monotypic: a taxonomic level containing a single lower level. Example - a genus consisting of a single species.), one has two species, and the very large and ubiquitous Isoperla genus containing most of the species anglers call Little Yellow Stones or Yellow Sallies. These are common hatches on our freestone streams during late spring and Summer.

The subfamily Perlodinae, or Springflies - contains thirty two genera in many sizes and colors including some important medium browns, yellows, and even some olives. It also includes the large Skwala Springflies of the West. As their group name implies, these are most common in the late winter through Spring.