Caddisflies

Caddisflies (Phylum Arthropoda, Class Insecta, Order Trichoptera) make up the largest and most diverse group of aquatic insects. More specifically, caddisflies are a group of small to medium-sized (2 to 30 mm in length), moth-like insects with two pairs of hairy membranous wings; they have aquatic larval forms that metamorphose into terrestrial adults. The name for the order Trichoptera comes from the name Trichos, which means “hairy,” and ptera, which means “wings.” The word “caddis” dates back to The Compleat Angler, written by Izaak Walton (1594–1683) and published in 1653, in which “cod-worms or caddis” were named as being used for bait. Caddisflies are a favorite food of many fish, and therefore are attractive to anglers, particularly trout fly fishermen, who tie artificial flies that mimic adult caddisflies. In Arkansas, more than 200 species in seventeen families are known. At least five caddisflies are endemic to the state.

Caddisflies are cosmopolitan in distribution, with greater diversity in warmer regions. They are associated with freshwater habitats, the larvae being found in lakes, ponds, rivers, streams, and other water bodies. There are approximately 14,500 described species worldwide within forty-five families including over 1,600 species in North America. Of the North American species, 229 total species have been reported for the Interior Highlands region, which includes parts of Arkansas, Missouri, Oklahoma, Illinois, and Kansas. In Arkansas, approximately 220 species in seventeen families have been documented, but that number will likely continue to rise. New caddisflies continue to be discovered and described yearly.

Fossil caddisflies have been found in strata dating back to the Triassic period about 250 million years ago. The largest numbers of fossilized remains are those of larval cases, but body and wing fossils of caddisflies are extremely rare. The finding of fossils in marine deposits in Brazil that resemble caddisfly larval cases may push back the origins of the order to about 300 million years ago in the early Permian Period.

Taxonomically, the order Trichoptera is divided into three suborders: Integripalpia, Annulipalpia, and Spicipalpia. The Integripalpia and Annulipalpia are established on the basis of the adult mouthparts, while the Spicipalpia is a small suborder that is unclear regarding relationships. Larvae of members of the suborder Integripalpia are polypod, poorly sclerotized detritivores that have abdominal prolegs in addition to thoracic legs, living permanently in tight-fitting cases as they move around the aquatic environment searching for food, while larvae of the Annulipalpia are considered campodeiform (free-living) well-sclerotized predators with long legs, dorso-ventrally flattened bodies, and protruding mouthparts that construct a fixed retreat in which they remain, waiting for food to come to them. Larvae of the third suborder, Spicipalpia, are free-living with no cases, but rather they create net-like traps from silk. Phylogenetically, the order Trichoptera is a clade that is sister to the order Lepidoptera (the moths and the butterflies), and more distantly related to the Diptera (true flies) and Mecoptera (Scorpionflies).

Regarding their life history, caddisflies are holometabolous insects—that is, they exhibit metamorphosis by passing through four development stages: egg, larva, pupa, and adult. The egg and pupal stages are considered as inactive, non-feeding periods. The larval stage is quite different morphologically compared to the adult. Larvae in North America pass through five instars, and the length of each larval period varies, with some as brief as two to three months with others taking about two years. With respect to life history of caddisflies in Arkansas, there are individual populations that have highly variable life cycles. Two-year (semivoltine), one-year (univoltine), and shorter (bi-multivoltine) life cycles exhibit either single or multi-cohort population patterns.

Caddisfly larvae are soft, more or less cylindrically shaped, caterpillar-like forms that occupy a wide variety of lotic (flowing water) and lentic (standing water) aquatic habitats. Some species are free-living predators, while others construct beautiful cases of silk, wood, leaves, or mineral fragments. Feeding strategies of larval caddisflies include being predators, leaf shredders, algal grazers, or collectors of particles from the water column. Caddisfly larvae play an important ecological role in the cycling of nutrients in aquatic ecosystems, especially in lotic habitats. Larvae also function as prey items for a host of vertebrates such as fishes, amphibians, birds, and small mammals. In addition, caddisfly larvae serve as important components of biological assessment programs due to their sensitivity to water quality and habitat degradation.

Adult caddisflies are terrestrial and do not feed or live long, perhaps only a few weeks. Adults are generally drab-colored and have long filiform antennae, large compound eyes, and tiny hairs covering the head, body, legs, and wings. Species may be distinguished on the basis of the palps, wing venation, and genitalia of both sexes. Adult trichopterans are crepuscular with a greater peak of activity shortly after dark than just before sunrise, or nocturnal. Caddisflies mate in the air, on the ground, or on vegetation near the water. Females oviposit in or near water shortly after mating. Adults are most abundant in Arkansas during the warmer months of the year, and the duration of the emergence of a species may extend over a period of days, weeks, or months depending upon the species involved and whether it occurs in the Coastal Plain or in the mountainous regions of the state. Adults may live for a few days or up to two or three months.

In Arkansas, there are at least five endemic caddisflies, which means they occur nowhere else on earth except Arkansas. Paucicalcaria ozarkensis is an endemic caddisfly from Gutter Rock Creek on Mount Magazine in Logan County. Others include Agapetus medicus from Benton, Clark, Hot Spring, Pike, and Polk counties; Helicopsyche limnella from Benton, Clark, Crawford, Franklin, Garland, Hot Spring, Johnson, Madison, Montgomery, Polk, Saline, and Washington counties; and Cheumatopsyche robisoni and Lepidostoma lescheni, the former found at sites in Garland, Montgomery, and Polk counties, and the latter collected from Mount Magazine.

For additional information:
Allen, Robert T. “Additions to the Known Endemic Flora and Fauna of Arkansas.” Proceedings of the Arkansas Academy of Science 42 (1988): 18–21. Online at http://scholarworks.uark.edu/jaas/vol42/iss1/8/ (accessed December 10, 2018).

———. “Insect Endemism in the Interior Highlands of North America.” Florida Entomologist 73 (1990): 539–569.

Bowles, D. E., and M. L. Mathis. “Caddisflies (Insecta: Trichoptera) of Mountainous Regions in Arkansas, with New State Records for the Order.” Journal of the Kansas Entomological Society 62 (1989): 234–244.

Bowles, D. E., M. L. Mathis, and J. S. Weaver III. “A New Species of Lepidostoma (Trichoptera: Lepidostomatidae) from Arkansas, U.S.A.” Aquatic Insects 16 (1994): 249–252.

Etnier, David A. “New Trichoptera Records from Arkansas and Missouri.” Proceedings of the Entomological Society of Washington 112 (2010): 483–489.

Flint, O. S., and Phoebe A. Harp. “Lepidostoma (Nosopus) ozarkense (Trichoptera: Lepidostomatidae), a New Species from Arkansas.” Entomological News 101 (1990): 81–87.

Floyd, M. A., J. K. Moulton, Guenter A. Schuster, and J. Robinson. “An Annotated Checklist of the Caddisflies (Insecta: Trichoptera) of Kentucky.” Journal of the Kentucky Academy of Science 73 (2012): 4–40.

Lago, P. K., and M. L. Mathis. “Records of Chimarra socia (Trichoptera: Philopotamidae) from Interior Highland Streams in Arkansas and Missouri.” Journal of the New York Entomological Society 97 (1989): 482–483.

Mathis, M. L., and D. E. Bowles. “A New Microcaddisfly Genus (Trichoptera: Hydroptilidae) from the Interior Highlands of Arkansas, U.S.A.” Journal of the New York Entomological Society 97 (1989):187–191.

McAllister, Chris T., Henry W. Robison, and Michael E. Slay. “The Arkansas Endemic Fauna: An Update with Additions, Deletions, a Synthesis of New Distributional Records, and Changes in Nomenclature.” Texas Journal of Science 61 (2009): 203–218.

Morse, John C. “A Checklist of the Trichoptera of North America including Greenland and Mexico.” Transactions of the American Entomological Society 119 (1993): 47–93.

Moulton, Stephen R., II., and Kenneth W. Stewart. “Caddisflies (Trichoptera) of the Interior Highlands of North America.” Memoirs of the American Entomological Institute 56 (1996): 1–313.

———. “The Nearctic Oecetis scala Group (Trichoptera: Leptoceridae) with the Description of Two New Species from the Interior Highlands.” Annals of the Entomological Society of America 86 (1993): 221–227.

———. “A New Species of the Polycentropus cinereus Group from Arkansas and Texas (Trichoptera: Polycentropodidae).” Entomological News 104 (1993): 35–38.

Robison, Henry W., and Robert T. Allen. Only in Arkansas: A Study of the Endemic Plants and Animals of the State. Fayetteville: University of Arkansas Press, 1995.

Robison, Henry W., and Chris T. McAllister. “The Arkansas Endemic Flora and Fauna: An Update with 13 Additional Species.” Journal of the Arkansas Academy of Science 69 (2015): 78–82. Online at http://scholarworks.uark.edu/jaas/vol69/iss1/16/ (accessed December 10, 2018).

Robison, Henry, Chris McAllister, Christopher Carlton, and Robert Tucker. “The Arkansas Endemic Biota: An Update with Additions and Deletions.” Journal of the Arkansas Academy of Science 62 (2008): 84–96. Online at http://scholarworks.uark.edu/jaas/vol62/iss1/14/ (accessed December 10, 2018).

Robison, Henry W., and Kenneth L. Smith. “The Endemic Flora and Fauna of Arkansas.” Proceedings of the Arkansas Academy of Science 36 (1982): 52–57. Online at http://scholarworks.uark.edu/jaas/vol36/iss1/17/ (accessed December 10, 2018).

Schuster, Guenter A., and David A. Etnier. A Manual for the Identification of the Larvae of the Caddisfly Genera Hydropsyche Pictet and Symphitopsyche Ulmer in Eastern and Central North America (Trichoptera: Hydropsychidae). Washington DC: Environmental Protection Agency, 1978.

Unzicker, J. D., L. Aggus, and L. O. Warren. “A Preliminary List of the Arkansas Trichoptera.” Journal of the Georgia Entomological Society 5 (1970): 167–174.

Wiggins, G. B. Larvae of the North American Caddisfly Genera (Trichoptera). 2nd Ed. Ontario: University of Toronto Press, 1996.

Henry W. Robison
Sherwood, Arkansas

Chris T. McAllister
Eastern Oklahoma State College