Caddisflies Order Trichoptera

Identification: Slender, elongate, mothlike insects. 1.5-25.0 mm. Antennae long and threadlike, usually as long as body or longer. 4 membranous wings (wings vestigial or absent in 9 of a few species): HW a little shorter than FW, the wings (especially FW) hairy; wings held rooflike over body at rest; wing venation rather generalized, with M usually 4-branched in FW and 3-branched in HW, and Cu 3-branched; wings generally with a small spot in fork of R4+5. Mouth parts reduced, best described as "sponging," palps well developed. Legs relatively long and slender. Tarsi 5-segmented. Metamorphosis complete, larvae aquatic. Similar orders: Lepidoptera (p. 218): wings covered with scales; usually with a coiled proboscis; maxillary palps generally absent or vestigial; M in FW 3-branched; no spot in fork of R4+5. Immature stages: Larvae are caterpillarlike, with a pair of hooklike appendages at posterior end of the body, and usually with filamentous gills on the abdominal segments. They are fairly active insects, and some move backward more often (and faster) than forward. Many larvae construct portable cases of various small objects fastened together with a gluelike substance or with silk;

PRIMITIVE CADDISFLY (p.214)

PRIMITIVE CADDISFLY (p.214)

as the larva grows the case may be enlarged, or the larva may leave and construct a new and larger case. Larval cases vary considerably, both in shape and in the materials of which they are made; they may be slender or oval, straight or curved, and made of bits of leaves, twigs, sand grains, or small pebbles. Each species makes a characteristic type of case. Larvae of some species construct silken nets and feed on material caught in the nets. Most larvae feed on plant materials, but a few (which usually do not make cases) are predaceous. When a larva is full-grown it attaches its case to some object in the water, then closes the case and pupates inside. The pupa, which usually has well-developed mandibles, cuts or works its way out of the case, crawls out of the water onto a stone or other object, and undergoes its final molt to the adult. Emergence of some species occurs at surface of water. Habits: Caddisflies are generally rather dull-colored insects, and their flight is jerky and erratic. They are largely nocturnal, spending the day resting in cool dark places; they are strongly attracted to lights at night. Eggs are laid in masses or strings, usually on stones or other objects in the water but occasionally on objects overhanging or near the water.

Importance: Caddisflies, particularly the immature stages, are an important item in the food of many freshwater fish. Classification: The N. American species are arranged in 17 families; these families are not grouped into superfamilies or suborders. No. of species: World, 4450; N. America, 975. Identification of families of Trichoptera: The chief characters used in separating families of caddisflies are those of the ocelli, maxillary palps, thoracic warts, and tibial spurs. Ocelli may be present or absent. The maxillary palps are usually 5-segmented, and the segments may differ in size and shape; the palps sometimes differ in form or segmentation in the two sexes. Thoracic warts are wartlike swellings on the dorsal surface of the thorax; they vary in size, number, and location in different families. Mounting a caddisfly on a pin often damages or destroys these structures; they are more easily studied in specimens preserved in alcohol. The tibial spurs are large, usually brownish, movable structures; there may be 1 or 2 at the apex of the tibia, and 1 or 2 located proximad of the apex. The leg spines are small, usually black structures.

Identification of the families of Trichoptera may be facilitated by dividing them into the following 5 groups:

1. Ocelli present or absent; some hairs on the wings clubbed; very small (1.5-6.0 mm.): Hydroptilidae.

2. Ocelli present; no wing hairs clubbed: Philopotamidae, Rhyacophilidae, Phryganeidae, and Limnephilidae.

3. Ocelli absent; no wing hairs clubbed; terminal segment of maxillary palps much longer than the other segments, and with faint cross striations: Psychomyiidae and Hydropsy chidae.

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