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Stonefly (Plecoptera) Glossary

Updated 22 December 2020

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  • abdomen - Segments at the back end of a stonefly containing the gut and reproductive organs. Does not have legs, wings (adults) or wingpads (larvae). The cerci, filaments, or tails are attached to the end of the abdomen.

  • allochthonous - Sources of carbon or nutrients from outside the stream. In the rocky mountains, most allochthonous materials are riparian plant leaves and pine needles that fall in the stream. Shredders such as Zapada spp. grow faster in the fall as there is more for them to eat. Also see http://en.wikipedia.org/wiki/Allochthonous

  • antennae - The first pair of appendages on the stoneflies head. Used for sensing the environment.

  • apterous - Without wings.

  • apomorphy - Similar characteristics that identify two or more animals as related. Used rather strictly when working on cladistics. Same as synapomorphy.

  • aquatic - A species that lives in water for part or all of its life.

  • B

  • Beringia - A prehistoric geographic province consisting of the unglaciated land north of the North American ice sheets during the various glaciation events. This area stretches between the Lena River in eastern Siberia in the west to the Richardson and McKenzie mountains on the eastern boundary of the Yukon Territory in Northern Canada. Biogeographers are interested in the animals and plants that survived glaciation in this area.

  • bifid - Forked into two or y-shaped. Sometimes forked at the very end.

  • biogeography - The study of species distributions over time. Events such as continental drift, orogenesis, glaciation and lowered sea levels forming land bridges among other things can affect species distributions. In the nearctic, the land bridge across the Bering strait during the last ice age affected many stonefly distributions.

  • brachypterous - Short winged See apterous and macropterous.

  • C

  • carinate - a body surface that is ridged or keeled.

  • carnivore - An animal (predator) that eats other animals (prey). They usually have piercing or cutting mouthparts. Scavenging, stealing prey from other predators and cannibalism are other ways some carnivores obtain food. Predator - prey relationships have been a popular arena of ecological research.

  • cercus or cerci - Tails or appendages at the end of the abdomen. Also called caudal filaments.

  • cervical - ventral or front side of neck.

  • cladistics - A branch of science that studies the evolutionary relationships between species. Scientists compare similiar traits between species. Sometimes it is clear when a trait changes in a closely related animal. This slightly changed trait is called a derived trait or similarity. Then scientists try to figure out when species branched off from each other and create the bush or tree-like diagrams (cladograms) you see with taxa names at the ends of the branches. This field is growing with the use of computers and genetic sequences. http://en.wikipedia.org/wiki/Cladistics

  • CPOM - Coarse Particulate Organic Matter. Leaves that fall in the stream. See FPOM

  • classification - Kingdom Animalia: Phylum Arthropoda: Class Insecta: Infraclass Neoptera: Superorder Exopterygota: Order Plecoptera: Suborder Arctoperlaria: Infraorder Euholognatha and Infraorder Systellognatha.

  • D

  • detritivore - An animal that eats decomposing organic matter. In streams and ponds, leaves that have fallen in the water are a major part of the diet.

  • diapause - A time when growth is suspended. Stonefly eggs may diapause after being laid and hatch months later to avoid difficult environmental conditions. Some stoneflies can diapause as nymphs. Of the species that have been studied so far, they diapause during their 4th, 5th or 6th instars.

  • diagnosis - insect description with excruciating detail and many perplexing fine illustrations. Sometimes needed to assist with bugs that are hard to identify. Diagnoses are usually published in peer reviewed scientific journals.

  • DNA barcoding - DNA barcoding is the analysis of a standardized segment of the mitochondrial cytochrome c oxidase subunit 1 (COI) gene. It can be used to identify unknown animals and associate nymphs and adults.

  • dorsal - The back or up side of a stonefly nymph. See ventral.

  • drumming - Stoneflies drum or tap their abdomens against the substrate to communicate with members of the opposite sex. See hammer and duet.

  • duet - As part of their mating rituals, adult stoneflies sometimes drum together, in a call and response pattern.

  • E

  • eclosion - a baby stonefly (or other invertebrate) hatching out of their egg

  • EMAP - Environmental Monitoring and Assessment Program. This is an Enivironmental Protection Agency biomonitoring program that collected macroinvertebrate and other data from 1996 to 2006 to develop better methods for ecological monitoring and risk assessment. The data is publicly available: http://www.epa.gov/emap/.

  • endemic - Found in a restricted geographical area. Not widespread, has a small range. For example Alloperla pilosa is endemic to Colorado while Amphinemura banksi and Doddsia occidentalis are endemic to western North America.

  • epiproct - the central adult male genitalia. Used to identify stoneflies to species. Of course rarely the absence of an epiproct also helps identify some species (i. e. Diura)

  • Euholognatha - An infraorder used to classify stonefly families. Includes Capniidae, Leuctridae, Nemoridae, Taeniopterygidae. Also see Systellognatha.

  • exopterygote - Member of the Superorder Exopterygota which includes insects whose immature insects resemble adults with externally developing wings in wingpads. They do not go through a pupal stage. Nymphs develop by molting through a series of instars.

  • exuvia - Molt skin or shuck. Since invertebrates (including stoneflies) don't have a skeleton, they support their body with a rigid exoskeleton made of chitin. As a result they need to shed their old skin in order to develop and grow larger. This shed skin is called an exuvia and may be caught in nets in the water or seen on rocks or vegetation near streams when the nymphs are emerging to their usually winged adult form. Flyfishermen may use shucks to help decide which artificial flies to fish with. See instar.

  • F

  • FPOM - Fine Particulate Organic Matter.

  • furcal pits - pits or depressions on the ventral side of the thorax. Used to identify Perlodidae nymphs. To see this, look through a microscope and flip the nymph on its back and study their chest between the middle legs. Hard to see on tiny or poorly preserved nymphs.

  • G

  • gill - used to absorb oxygen from the water. If a stonefly has gills they are always fingerlike, never flat plates like mayflies. Plecoptera may variously have gills attached to the neck or cervical region, the thorax and or only the first few or very last segments of the abdomen in one of our more primitive families the Perlidae. Since stonefly gills are mostly used for osmoregulation, a better term is osmobranchia
  • glossae - Mouthpart, the two middle lobes of the labium. Sometimes hard to see in tiny or poorly preserved specimens. To view this feature, flip the nymph on its back and try to hold the head up or back so you can look at the underside or ventral side of the head. The nymphs, even though dead may resist this, be firm but gentle. See paraglossae, labial palp.

  • Glossae = the pair in the center
    Paraglossae = middle pair of appendages, considered equal to the glossae in this drawing.
    Labial palps = outside multi-segmented appendage


  • hammer - Many male stoneflies have a hammer on the underside of their abdomen. They use it to attract a mate by drumwing on the branches of riparian vegetation, rocks or the ground.

  • hemimetabolous - Also referred to as incomplete metamorphosis. Stoneflies go through three life stages; egg, nymph and adult. As a result the adults somewhat resemble the larvae and may retain larval gills or other traits. This is in contrast to homometaboulous insects which have a pupal stage between the larvae and adult stages.

  • hemocyanin - These are proteins that transport oxygen in the hemolymph of some, but not all stonefly species. They are metalloproteins with two copper atoms that reversibly bind a single oxygen molecule (O2). Oxygenation causes a color change between the colorless Cu(I) deoxygenated form and the blue Cu(II) oxygenated form. (edited from wikipedia)

  • hexamerin - Hexamerins are hemocyanin-derived proteins that are used by stoneflies as storage protiens. As they evolved from hemocyanin they lost the ability to bind copper ions and transport oxygen.

  • holarctic - An ecozone including both the nearctic and palearctic. This is the entire northern temperate and boreal portion of our planet. Gunnison County, Colorado is both nearctic and holarctic.

  • I

  • instar - the nymph between molts. Time spent in each instar depends on the length of the life cycle. Stoneflies seem to have an indeterminate number (10-22+) of instars between hatching from their egg to emerging as an adult. They may moult fewer or more times depending upon environmental conditions. Many stonefly species have not had instar analysis done in the field or lab yet.

  • ITIS - The Integrated Taxonomic Information System http://www.itis.gov/ provides taxonomic information on plants, animals, fungi, and microbes of North America and the world. They are a partnership of U.S., Canadian, and Mexican agencies (ITIS-North America); other organizations; and taxonomic specialists. ITIS is also a partner of Species 2000 and the Global Biodiversity Information Facility (GBIF). The ITIS and Species 2000 Catalogue of Life (CoL) partnership is proud to provide the taxonomic backbone to the Encyclopedia of Life (EOL). [This text was copied from their website on 2 June 2010.] They also assign Taxonomic Serial Numbers.

  • J


  • keel - carina or elevated ridge.

  • krenel - stream arising from a spring. See kryal and rhithral.

  • kryal - the section of a stream or river arising from glacial, permafrost or a permanent snowfield. See krenel and rhithral.

  • L

  • labial palp - segmented mouthparts on the outside of the labium. Has chemoreceptors used to feel and taste. See paraglossae

  • lacinia - mouthpart, the inner bladelike part of the maxillae. Often has teeth, brushes, spines or knobs used for identification.

  • lotic - about flowing water, streams or rivers, habitat for stoneflies.

  • M

  • macropterous - long winged. Most stonefly adults are long winged. See apterous (no wings) and brachypterous (short-winged).

  • median tolerance limit - The median number of animals that survive a stressor such as high temperatures, heavy metals or low oxygen. Tests are run for a specific amount of time such as 96 hours. Sometimes abbreviated TLm96 or TLM.

  • monophyletic - from greek: of one stem. All the creatures under discussion share a common ancestor and all descendants of the ancestor are included.

  • multivoltine - Life cycle short enough to have several generations per year. Leads to the observation of several adult flight periods per year in light traps.

  • N

  • naiad or nymph- immature aquatic nymph or larvae. Lives mostly in streams or rivers.

  • nearctic - The nearctic ecozone includes most of North America, Greenland and the mountains of Mexico. (Southern Florida is in the Neotropic ecozone.) Colorado is in the nearctic. There are a total of 8 terrestrial ecozones on our planet.

  • nomenclature - the system of naming things. Changes in stonefly nomenclature over the years make old papers and keys hard to read until you are familiar with the name changes. In spite of the occasional frustration we suffer dealing with this, the name changes usually make sense when you look carefully at the bug under consideration. I translated the old names to new ones for some of the papers in the bibliography for this website. Stewart and Stark's excellent book "Nymphs of North American Stonefly Genera" has a review of name changes too. Here are some useful links:
         Curiosities of Biological Nomenclature by Mark Isaac - fun and a good introduction to scientific names.     http://curioustaxonomy.net/
         Integrated Taxonomic Information System -Check if names have changed http://www.itis.gov/

  • O

  • ocelli - Simple eyes or light detecting organs on the top of the head of an adult stonefly. Ocelli look like little dark shiny hemispheres. Stoneflies also have compound eyes.

  • omnivore - An animal that eats both plant and animal matter.

  • orogenesis - Mountain building. This term is used sometimes to explain speciation events.

  • osmobranchia
  • - protrusions of the stonefly integument used to osmoregulate or exchange ions with the water to maintain proper concentration of electrolytes and fluid balance. Usually referred to as gills.


  • palaearctic or palearctic - term used to describe the home range of an organism. The palearctic ecozone includes Europe, northern Asia, northern Africa, and the northern and central Arabian Peninsula. Habitat is mostly temperate or boreal. Many species are closely related to the species in Gunnison County. See nearctic.

  • paraglossae - mouthpart used taxonomically to split the carnivorous stonefly families from the detritivorous families. Specifically, its the lateral terminal lobe of the labium. See glossae and labial palp.

  • Glossae = the pair in the center
    Paraglossae = middle pair of appendages, considered longer than the glossae in this drawing,
    Labial palps = outside multi-segmented appendage
  • plesiomorphy - An ancestral trait common to an entire clade or group of related stoneflies. Used when discussing cladistics.

  • prognathous - Having a protruding lower jaw. For example in stoneflies, the lower mouthparts including mandibles and lacinia may even protrude beyond the upper part of the face in some species. Hypognathous is a synonym.

  • Q


  • rheocrene - A spring that emerges from the ground to become a stream immediately. There is enough water to flow and maintain at least a small stream.

  • rhithral - stream or river where the main source of water is from snowmelt or precipitation. See krenel and kryal.

  • riparian - Wetland zone or area bordering a stream or river. Some characteristic plants in the Gunnison basin include willow (Salix), sedges (Carex) and Aspen (Populus) or Spruce/Fir (Picea/Abies) forest. The riparian zone is essential habitat for adult stoneflies.

  • RIVPACS - River Invertebrate Prediction and Classification System. A biomonitoring model that statistically compares Observed species in study streams to Expected macroinvertebrate species in reference streams (O/E ratio). This model ignores abundance of insects.

  • S

  • semivoltine - The entire life cycle from egg to nymph to adult and back to egg takes two years.

  • sensu lato
  • - taxonomically inclusive, includes more species than sensu stricto.

  • sensu stricto or stricto sensu - Taxonomists use these latin phrases to indicate "in the stricter sense", abbreviated s.s. Stricto sensu is often used when discussing a subgenera with the same name as the genus under consideration. This may apply to other taxonmic levels such as families or species.

  • shredder(s) - organisms who eat leaves and poop fine particle organic matter (FPOM). They are an important part of detritus processing and nutrient cycles in freshwater habitats. Shredders often have a life cycle adapted to the large influx of leaves into the water during leaf drop in the fall. My favorite family of stonefly shredders in the Gunnison Basin is the Nemouridae.

  • STORET - STOrage and RETrieval Data Warehouse. Created by the Environmental Protection Agency to share macroinvertebrate and other data. http://www.epa.gov/storet/

  • synapomorphy - A morphological feature that related insects have and unrelated insects do not have. Used to infer common ancestry. A shared, derived taxonomic or genetic character. Same as apomorphy.

  • synonym - Two or more names used for the same organism. There is always a commonly accepted name and various historic names are considered synonymies. Synonymies occur in several ways. One is when a species is described by two people independently. Another is when species are consolidated (lumped) or split into a genera. In these cases, the oldest species name (by date of publication) is always retained. Changes in generic names are common when a group of insects are taxonomically revised by experts. You can use the Integrated Taxonomic Information System to check if a species name has been synonymized.

  • systellognatha - An infraorder used to classify stonefly families. Refers to the carnivorous stonefly families that have labial mouthparts with the paraglossae longer than the glossae. Includes the families Chloroperlidae, Isoperlidae, Perlidae and Perlodidae. Used by Frison in his revisions of 1935 and 1942.

  • systematics - a branch of science that assigns scientific names to organisms. There were large changes in plecoptera systematics during the 19th and 20th centuries. Some of the publications that relate directly to Gunnison Basin plecoptera such as Knight and Gaufin (1966) have old names and may be difficult to interpret until the reader translates the nomenclature changes. Chapter 16: Guide to Changes in Generic Names in Stewart and Stark (2002) is a helpful overview. Bill Stark's Nearctic Stonefly List http://www.nearctica.com/nomina/oddbugs/plecop.htm has synonyms too.

  • T

  • thorax - The three segments behind the head. Labeled from the first segment behind the head and to the back: prothorax, mesothorax, metathorax. Each segment has a pair of legs in both nymphs and adults. Most adults have wings attached to the mesothorax and metathorax.

  • TSN - Taxonomic Serial Number, a unique number for each species, genera, and all taxnomic levels created by Integrated Taxonomic Information System for use in databases. The TSN for each species is in the upper right corner of the animals webpages on gunnisoninsects.org

  • U

  • univoltine - One year life cycle. See multivoltine and semivoltine

  • USGS - United States Geological Survey. They provide many kinds of data and maps. For example, they host the valuable Stoneflies of the United States website http://www.npwrc.usgs.gov/resource/distr/insects/sfly/sflyusa.htm edited by Boris Kondratieff and Ken Baumann.

  • V

  • ventral - The bottom, underside or stomach side of a Plecoptera nymph. See dorsal

  • voltinism - Number of years it takes the stonefly to complete its life cycle from egg through nymph, adult and back to the egg. See multivoltine, semivoltine and univoltine

  • W

  • Website Index

  • wingpad - Wing developing in its container attached to the meso and meta-thorax of older stonefly nymphs. Mature nymphs have large conspicuous wingpads. Right before the stonefly emerges the wingpads may turn black or begin to puff up to be ready for emergence. Sometimes you can see the highly folded adult wings inside the wingpads.

  • X




    Peckarsky,BL; Fraissinet,PR; Penton,MA; Conklin Jr.,DJ 1990 Freshwater Macroinvertebrates of Northeastern North America. Cornell University, Ithaca, NY. 442 pages.
          Has a glossary at the end with useful definitions for the wide variety of taxa discussed in the book.

    Stewart,KW and Stark,BP 2002 Nymphs of North American Stonefly Genera. 2nd edition The Caddis Press, Columbus, Ohio. 510 pages.
          The introductory chapters were used heavily to develop this glossary.

    Wikipedia - http://en.wikipedia.org/wiki/Main_Page

    Brown,WS 2004 Plecoptera or Stoneflies of Gunnison County, Colorado

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