Chloroperlidae

Chloroperlidae are defined mainly by the lack of distinct pigment patterns on the thorax, a relatively short cerci compared to the abdomen, slender labial palps, wings pads which are not divergent from the midline and short legs.[9] Adult Chloroperlidae are typically yellowish green in coloration, which gives them their common name.

Insects in this family are small to medium-sized, ranging from 6 to 20 mm[6] or 10 to 20 mm[10] and have a distinct green colour for their wings, which gives the common name green stoneflies.[3] They can also be yellow, and fly fishermen commonly refer to them as yellow sallflies or yellow sallies.[11] Chloroperlidae undergo incomplete metamorphosis, only having three life stages (egg, nymph, and adult), but no pupal stage.[7] In the nymph stage, they have almost-parallel hindwing pads to their brown to yellow body, short legs and cerci smaller than their abdomen.[3] As they become adults, their body and wings become oval-shaped and can be somewhat green, yellow, or white.[3]

Chloroperlidae is a family of stoneflies, typically referred to as green stoneflies, and is part of the order Plecoptera, splitting off into its lineage roughly 150 million years ago.[2] This classification as a separate family was originally made in 1912.[2] There is some contention about Chloroperlidae’s classification, however, with some arguing it is a subfamily within Perlidae, some arguing it is its own family within Perlomorpha, and others believing it is its own family within Perloidea.[2] It is composed of more than 200 species.[3][2][1]

Subfamilies & genera

Two subfamilies are included by the Plecoptera Species File:[12]

More than 200 species of the Chloroperlidae family are distributed predominantly in the Holarctic region.[1][5] Nearly 80 species distributed among the Nearctic and East Palaearctic Regions are in the genera Sweltsa and Alloperla.[5] Four genera and 19 species still exist in Europe.[5]

Estimated Chloroperlidae species divided among continents are 95 in North America, 2 in Central America, 19 in Europe, 1 in Africa, and 89 in Asia.[5] Estimated Chloroperlidae species by zoogeographical region are 20 in the Palaearctic Region, 95 in the Nearctic Region, 2 in the Neotropical Region, with a total species number of 206 in the World.[5] Estimated Chloroperlidae genera by zoogeographical region are 14 in Palaearctic, 12 in Nearctic, 2 in Neotropical, 2 in Oriental, with a total genera number of 17 in the World.

Nymphs are aquatic and inhabit a wide variety of habitats, especially in the stony bottoms of cold mountain streams and/or lakes.[6][13] The family Chloroperlidae is not very tolerant to pollutants, making them a good indicator species of very high water quality.[6][4] Suwallia pallidula nymphs dwell in the hyporheic zone emerging only when are going to become winged adults.[14] This shows the importance of the hyporheic zone prior to their emergence, but also the challenges for further research on early instars and voltinism.[14] As winged adults, they migrate onto land where they dwell on rocks, debris, and plants near the water.[3][7]

Chloroperlidae are hemimetabolous (undergo incomplete metamorphosis), with no pupal stage and three life stages: egg, nymph, and adult.[7]

The Chloroperlidae life cycle begins with an egg. Adult females deposit egg sacs containing fertilized eggs into a water body either by dropping the sac above the water body, releasing eggs from the banks of a water body, or by depositing egg sacs along the gravel substrate.[7] If circumstances are unfavourable for hatching, the eggs may enter diapause for 3 to 12 months.[7] Otherwise, the eggs may hatch within 2–3 weeks or a few months.[7]

After the eggs hatch, the nymph stage of the cycle begins. Chloroperlidae nymphs reside in the benthic portions of the water body among and within the gravel and sediment.[6] As the nymphs mature, they undergo 12-23 developmental stages,[15] or instars, and progressively grow larger and more mature by shedding their exoskeleton.[7] They also grow wing pads as they develop, which become functioning wings as adults.[7] After approximately one year of development, the nymphs undergo their final moult and become adults, emerging from the water body in the spring or summer.[6] Male Chloroperlidae mature faster, and therefore emerge earlier than females.[15]

The objective for Chloroperlidae adults is to find a mate and reproduce.[6][15] Most Chloroperlidae do not feed; their sole focus is mating.[6][15] However, some species with longer adult stages do feed, to maintain enough energy to both evade predators and find a mate.[8] To attract a mate, males land on a rock or piece of vegetation near the water and produce sounds by striking their abdomen against an object of their choice.[7] The sound attracts nearby females of the same species, and an interested female will make the same sound back to the male.[7] Once they locate each other, they mate, with the male depositing his sperm directly into the female's reproductive organs to fertilize her eggs.[7] Mating Chloroperlidae are often found in swarms, clustered around vegetation near a water body.[15] Chloroperlidae are polygynous, and males that emerge early are larger and more likely to be successful in reproducing with multiple females.[15][16] After fertilization, the eggs are deposited in the nearest body of water.[7] The flies then die soon after mating, as the adult stage of Chloroperlidae lasts only 1–4 weeks.[7]

Chloroperlidae consume food, but they are also an important food source for many fish and invertebrates in freshwater ecosystems.[7]

• Data related to Chloroperlidae at Wikispecies
• Media related to Chloroperlidae at Wikimedia Commons