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Order Trichoptera

(Caddisfly)

(View: lateral, out of house)

Updated: October 09, 2013      

Contents:

• Linnean system of hierarchical classification
• Introduction
• Life History
• Habitat and Distribution
• Distribution of the families of Trichoptera, together with typical larval habitats
• Feeding
• Indicator value
• Physiological and ecological tolerances and requirements
• Pictures of the houses
• References and web URLs

Linnean system of hierarchical classification (Williams & Feltmate, 1992):

• Superphylum Arthropoda
• (jointed-legged metazoan animals [Gr, arthron = joint; pous = foot])
• Phylum Entoma
• Subphylum Uniramia
• (L, unus = one; ramus = branch, referring to the unbranched nature of the appendages)
• Superclass Hexapoda
• (Gr, hex = six, pous = foot)
• Class Insecta
• (L, insectum meaning cut into sections)
• Subclass Ptilota
• Infraclass Neopterygota

Introduction

The wings of Trichoptera are covered with setae, from which the name of the order is derived (from the Greek "trichos"= hair, and "pteron"=wing).

Three superfamilies have been distinguished, which include five groups based on case-building behaviour. Hydropsychoidea (Hydropsychidae, Philopotamidae, Polycentropodidae, and Psychomyiidae) are the net spinners and retreat makers; Rhyacophiloidea include the free-living forms (Rhyacophilidae), saddle-case makers (Glossosomatidae), and purse-case makers (Hydroptilidae); and Limnephiloidea are the tube-case makers.

Life History

Mass emergences of some species from large rivers are considered a nuisance by residents, since the insects are attracted to outdoor lights; human allergies to the scales on their wings have also been reported. The larvae of some leptocerids are reported to damage the young shoots of rice plants in paddy fields. The larvae of a few species are known to eat fish eggs. On the beneficial side, many hydropsychids prey on black fly larvae.

Many species that inhabit temporary ponds lay eggs in the basins of dry pools in the fall, when the soil surface is beginning to become more moist. After larvae hatch, they may remain within the gelatinous matrix for months until the pool basin is reflooded. Moisture is the apparent stimulus for larvae to break out of the gelatinous matrix and begin case building or net spinning.

Adult caddisflies differ from moths in a number of aspects foremost amongst which are patterns of wing venation and structure of the mouthparts. Adult caddisflies are small (1.5 mm body length) to moderate-sized (4.0 cm), tend to be drab in colour, and are mostly active at night, especially around lights. During the day they hide in riparian vegetation. The compound eyes are well developed and there may be up to three ocelli. The mouthparts are weak and are capable only of ingesting liquids. All three thoracic segments are distinct. The legs are long and slender.

Caddisfly larvae are quite similar to lepidopteran caterpillars but have only a single pair of abdominal prolegs which are located on the terminal segment and are each equipped with an apical anal claw. The larval thorax is well developed, with at least the pronotum covered dorsally by a pair of sclerotized plates.

The trichopteran pupa is exarate and, in case-building species, develops within the larval case after it has been secured to the substrate and sealed with silk. In free-living species, the final instar larva builds a special pupal case, generally made from silk and mineral particles, again this is firmly attached to the substrate. In most species, the pupa is equipped with heavily sclerotized mandibles which enable it to cut an opening in the case so that it may escape and swim to the water surface.

Habitat and Distribution

At present, caddisflies inhabit a wide range of habitats from the ancestral cool streams to warm streams, permanent lakes and marshes, and permanent and temporary ponds. One species has been found in tide pools off the coast of New Zealand; the females oviposit through the papillar pores of starfishes. Caddisflies have been generally classified as clingers, sprawlers, or climbers, although a few are burrowers.

Although caddisfly larvae are found in a wide range of aquatic habitats, the greatest diversity occurs in cool running waters. Furthermore, in families represented in both lotic and lentic habitats, the genera exhibiting more ancestral characters tend to be found in cool streams whereas those showing more derived characters tend to occur in warm, lentic waters. These two findings point to cool, running waters as the most likely primordial caddisfly habitat, the one in which the ancestors of the Trichoptera first became aquatic and the one in which differentiation into the basic groups (superfamilies) took place (Williams & Feltmate, 1994).

Distribution of the families of Trichoptera, together with typical larval habitats (Williams & Feltmate, 1992)

A final point worth mentioning about the Trichoptera, in general, and about those that live in small streams in particular, concerns habitat specificity. Many species that are restricted to small streams reflect the ecological characteristics of the surrounding terrestrial community. In such streams, conditions for the larvae are affected by shade in summer or winter, the amount and periodicity of leaf-fall, and the distribution of local precipitation, all three of which are integrated with the type of climax community occupying the general area. As a result, there is, in general, a marked correlation between these terrestrial biomes and the ecological affinities of their respective small-stream caddisfly faunas. Such correlations are of enormous importance to palaeoecology, and caddisfly remains are proving to be a powerful tool in the interpretation and reconstruction of past environments (Williams & Feltmate, 1994).

Feeding

Indicator value

At present, caddisflies inhabit a wide range of habitats from the ancestral cool streams to warm streams, permanent lakes and marshes, and permanent and temporary ponds. One species has been found in tide pools off the coast of New Zealand; the females oviposit through the papillar pores of starfishes.

Although caddisfly larvae are found in a wide range of aquatic habitats, the greatest diversity occurs in cool running waters. Furthermore, in families represented in both lotic and lentic habitats, the genera exhibiting more ancestral characters tend to be found in cool streams whereas those showing more derived characters tend to occur in warm, lentic waters. These two findings point to cool, running waters as the most likely primordial caddisfly habitat, the one in which the ancestors of the Trichoptera first became aquatic and the one in which differentiation into the basic groups (superfamilies) took place. (Williams and Feltmate, 1992)

Mass emergences of some species from large rivers are considered a nuisance by residents, since the insects are attracted to outdoor lights; human allergies to the scales on their wings have also been reported. The larvae of some leptocerids are reported to damage the young shoots of rice plants in paddy fields. The larvae of a few species are known to eat fish eggs. On the beneficial side, many hydropsychids prey on black fly larvae.

Some physiological and ecological tolerances and requirements (Mackie, 2001)

Pictures of the houses

Family: Molanidae

View: Emerging from house

Examples of Trichoptera houses

References and web URLs:

• Hutchinson, G.E. 1993. A Treatise on Limnology. Vol. IV, The Zoobenthos. Ed. Y.H. Edmondson. John Wiley & Sons, Inc. Xx, 944pp.
• Mackie, G.L. 2001. Applied Aquatic Ecosystem Concepts. Kendall/Hunt Publishing Company. xxv, 744 pp. ISBN 0-7872-7490-9
• Narf, R. 1997. Midges, bugs, whirligigs and others: The distribution of insects in Lake "U-Name-It". Lakeline. N. Am. Lake Manage. Soc. 16-17, 57-62.
• Peckarsky, B.L., P.R. Fraissinet, M.A. Penton, and D.J. Conklin, Jr. 1990. Freshwater Macroinvertebrates of Northeastern North America. Cornell Univ. Press. xii, 442pp.
• Wetzel, R.G. 1983. Limnology. 2nd ed. Saunders College Publishing. Xii, 767pp, R81, I10.
• Williams, D.D., and Feltmate, B.W. 1992. Aquatic Insects. CAB International. ISBN: 0-85198-782-6. xiii, 358p.

• Mandaville, S.M. 1999. Bioassessment of Freshwaters Using Benthic Macroinvertebrates-A Primer. First Ed. Project E-1, Soil & Water Conservation Society of Metro Halifax. viii, Chapters I-XXVII, Appendices A-D. 244p.
  • For the entire Report, download all the files in the subdirectory, Primer1
  • Chapter VII: Order Trichoptera (caddisflies)
• Tree of Life
• New York Department State of Environmental Conservation

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