Leptoceridae
Leptocerus interruptus
Scientific classification
Domain:	Eukaryota
Kingdom:	Animalia
Phylum:	Arthropoda
Class:	Insecta
Order:	Trichoptera
Superfamily:	Leptoceroidea
Family:	Leptoceridae Leach in Brewster, 1815

The family Leptoceridae are a family of caddisflies often called "long-horned caddisflies" or "silverhorns". Leptoceridae is the second largest family of caddisflies with over 1850 species in approximately 68 genera. ^[1] They can be found throughout most continents and are common, widespread, and often locally abundant. The main identifying feature of most Leptoceridae is that their antennae are much longer than those of other caddisflies. There is one genus with relatively short antennae ( Ceraclea), but it is easily identified by the pair of dark curved lines on the mesonotum.

Etymology

"Leptoceridae" comes from the Greek roots "leptos" and "keras", which means "slender" and "antenna". ^[2]

Larvae

Larval Description

Unlike in other caddisfly families, the larval antennae are long, close to the front edge of the head, and large enough to see with a hand-lens. Hindlegs are much longer than the two front pairs of legs, slender, and fringed with fine hairs. The legs are somewhat modified, with the trochanter being lengthened, the femur subdivided into a short proximal and a longer distal section, and the tibia is lengthened and usually subdivided into two parts by a constriction near the middle. Larvae have three indistinct humps on the first abdominal segment. The mesonotal plates are lightly sclerotized and often have little pigmentation. Lines between the plates of the prothorax and the head are unpigmented; these lines are the points of weakness where the primary sclerites of the head and thorax subdivide at ecdysis. Spinose sclerites occur on the lateral humps in some genera. Abdominal gills are usually single, sometimes in groups or lacking. Forked lamellae are confined to segment 8. Segment 9 bears a small dorsal sclerite with setae. Spines occur on the base of the anal prolegs in some genera. ^{[2] [3]}

Swimming

Leptoceridae larvae have dense swimming hairs and long hindlegs that protrude outside of their case, which enable them to be surprisingly effective swimmers. Larvae swim with their cases by gripping the case with their anal hooks and sweeping their long, hairy legs at a wide angle. Swimming allows the larvae to quickly move among aquatic vegetation in search of food or shelter. Larvae of one leptocerid, Triaenodes tardus, can swim continuously for up to six minutes. ^[4] Larval case architecture is characteristic for each genus and can be made of many different materials. ^[3]

Ecology

Leptocerid larvae exhibit a wide range of water quality tolerances and feed on a wide variety of foods, ranging from detritus and algal grazing to predation of freshwater sponges. ^[5] Feeding guilds include scrapers, shredders, and predators. ^[2] They occupy ponds, marshes, lakes, and the slower currents of streams, especially where aquatic plants are found. Specific habitat, water quality, and dietary requirements differ between species.

Pupae

During the early stages of metamorphosis, pupating leptocerids flush the last layer of larval skin through the posterior opening of their cases. Molannidae is the only other caddisfly family that does this. The long, delicate antennae wrap around the tip of the pupal abdomen. ^[2]

Adults

Adult Description

Antennae are exceptionally long (except Ceraclea), with males generally having antennae 2x the length of the forewing and females having antennae 1.5x the forewing length. Adults always have apical spurs, but no preapical spurs on the middle and hind tibia, and 0, 1, or 2 spurs on the front. Maxillary palps are five-segmented in both sexes and are long, especially in the outermost segment. The wings are relatively long and slender. Another unique feature of adult leptocerids is that the front- and hindwings are mechanically joined together by an arrangement of hairs. ^[2]

Courtship and Reproduction

Leptoceridae are unique among Trichoptera in having their fore- and hindwings highly synchronized during flight, which may allow them to perform more acrobatic flights than other caddisflies. ^[6] Male leptocerids generally form dense swarms over waterbodies to court females. Larger species generally perform larger swarming movements and swarm further from the shore. Males can vary in body size and flight capability, which likely influences their reproductive success. ^[7]

Leptoceridae perform three types of swarming flight patterns and pair formation behaviors. Male Athripsodes and Ceraclea fly in horizontal zigzag patterns over the surface of the water. Females fly into these swarms and are grabbed by the males midair, couple their genitalia, and continue flying while mating or carry their partner to nearby vegetation to finish copulating. Only the male use its wings; the female hangs upside-down from the coupling. Similarly, male Mystacides fly in vertical zigzag patterns over water and vegetation and grab approaching females. However, both partners use their wings to fly in tandem and do not couple their genitalia midair. They fly together to the shore to copulate. Male Triaenodes fly in a mixture of both horizontal and vertical zigzagging, where they search for females perched on aquatic plants. When a female is found, the male lands next to it and copulates while clinging to the plant for a long time. ^[7]

These differences in flight patterns and pair formation behaviors correlate with three types of sexual dimorphism. Males of species that fly while copulating have longer forewings than their female partners. Males of the vertically zigzagging species have larger eyes, enabling them to more easily detect females that approach the swarm. Males of species that do not fly while copulating are much smaller than their female partners. ^[7]

Most leptocerid females lay their eggs as a green gelatinous mass on the water's surface, although Nectopsyche deposit their eggs as strings. ^{[8] [2]} The eggs float on the surface until they swell with water and sink.

Parasitism

Adult leptocerids are more commonly parasitized than other caddisfly families, possibly due to the unique presence of respiratory slits (serving as an opening) on their bodies. Aquatic mites of Hydracarina, Aturidae, and Pionidae, and Mermithidae nematodes have been found to parasitize adult Nectopsyche. Cypridae ostracods have been found to parasitize Nectopsyche larvae. ^[8]

Genera

The type genus for Leptoceridae is Leptocerus W.E. Leach, 1815. ^[9]

These 68 genera belong to the family Leptoceridae (not all listed below):

Data sources: i = ITIS, ^[9] c = Catalogue of Life, ^[10] g = GBIF, ^[11] b = Bugguide.net ^[12]

References

External links