''Dolophilodes distinctus'' is a

species In biology, a species is the basic unit of classification and a taxonomic rank of an organism, as well as a unit of biodiversity. A species is often defined as the largest group of organisms in which any two individuals of the appropriate s ...

of caddisfly in the

Philopotamidae Philopotamidae is a family of insects in the order Trichoptera, the caddisflies. They are known commonly as the finger-net caddisflies.larva A larva (; plural larvae ) is a distinct juvenile form many animals undergo before metamorphosis into adults. Animals with indirect development such as insects, amphibians, or cnidarians typically have a larval phase of their life cycle. The ...

e are found in streams in eastern North America where they build net-like retreats.

Description

Adult caddisflies are small moth-like insects; the adult ''Dolophilodes distinctus'' has brown wings with darker brown markings. Adult females emerging in summer are winged while those emerging in March are often

brachypterous Brachyptery is an anatomical condition in which an animal has very reduced wings. Such animals or their wings may be described as "brachypterous". Another descriptor for very small wings is microptery. Brachypterous wings generally are not functi ...

(have vestigial wings). These sometimes breed on the snow that is lying on the ground at this time of year.

Distribution

''Dolophilodes distinctus'' is native to eastern North America. It is a common species whose range extends from

Minnesota Minnesota () is a state in the upper midwestern region of the United States. It is the 12th largest U.S. state in area and the 22nd most populous, with over 5.75 million residents. Minnesota is home to western prairies, now given over to ...

and

Newfoundland Newfoundland and Labrador (; french: Terre-Neuve-et-Labrador; frequently abbreviated as NL) is the easternmost province of Canada, in the country's Atlantic region. The province comprises the island of Newfoundland and the continental region ...

southwards to Georgia. They are usually found in clear montane streams.

Ecology

Like other members of Philopotamidae, the larvae of ''D. distinctus'' is free-living and builds a net to intercept the fine organic particles drifting downstream. In streams in

Ontario Ontario ( ; ) is one of the thirteen provinces and territories of Canada.Ontario is located in the geographic eastern half of Canada, but it has historically and politically been considered to be part of Central Canada. Located in Central Ca ...

, this species was found in shallow streams with small pools joined by riffles. In one stream with clear hard water, the stream bed was limestone gravel interspersed with sand and patches of clay, and in a different, brown-water, stream it was granite gravel mixed with assorted size cobbles. In the limestone gravel location, larvae at various stages of development were found to be present all year, with peak numbers in August, and emergence occurring for much of the time between late June and late August; some emergence possibly happened in mid-winter as well. The larva builds a net consisting of an elongated sac made of a meshwork of fine

silk Silk is a natural protein fiber, some forms of which can be woven into textiles. The protein fiber of silk is composed mainly of fibroin and is produced by certain insect larvae to form cocoons. The best-known silk is obtained from the coc ...

strands. The longitudinal strands are stout and the transverse strands are finer and closer together. In the final

instar An instar (, from the Latin '' īnstar'', "form", "likeness") is a developmental stage of arthropods, such as insects, between each moult (''ecdysis''), until sexual maturity is reached. Arthropods must shed the exoskeleton in order to grow or ass ...

, the sac may be up to long and in diameter, with extra silk threads at the upstream end to anchor it to the stream bed and nearby rocks. It has been estimated that the net made by the final instar larva is composed of over a kilometre of silk and has 100 million rectangular mesh openings. The net is usually built underneath a rock where a current of water flows through it. The downstream end of the net is free to move and has an opening to permit a respiratory current to flow through, and groups of nets are often built besides each other. The larva moves about inside the net and feeds on the fine organic matter and

diatom A diatom (Neo-Latin ''diatoma''), "a cutting through, a severance", from el, διάτομος, diátomos, "cut in half, divided equally" from el, διατέμνω, diatémno, "to cut in twain". is any member of a large group comprising sev ...

s that get caught in the mesh structure. Much of its time is spent scraping this deposit off the net with specialised mouthparts.

References

{{Taxonbar, from=Q2319114 Trichoptera Insects of North America Insects described in 1852