Stoneflies

Plecoptera.

This is a small order of very ancient and primitive insects whose nymphs are typical inhabitants of streams. The adults remain near the nymphal habitat and are frequently found resting on rocks or boulders in midstream (hence their common name) or on nearby vegetation and tree trunks.

Adult stoneflies are soft bodied, small to medium-sized (most with length to tips of folded wings 1—2 cm, but some to 4-5 cm), and rather elongate in overall form. Except for a few with stubby or no wings, all possess two pairs of complete wings with a fairly complex venation: the fore wing is long, with parallel sides; the hind wing has a large, fanlike area posteriorly. Stoneflies are drably colored in browns and grays, except for some South American Eustheni-idae that have wings splashed with bright reds and yellows. The antennae and cerci (when present) are both filiform, the former much longer than the latter. Mouth-parts are mandibulate but with weak elements. Between the two suborders, the Arctoperlaria and Antarctoperlaria, there is a basic difference in food habits corre

Figure 6.4 DOBSONFLIES AND STONEFLIES. (a) Dobsonfly (Corydalus cornutus, Corydalidae). (b) Dobsonfly (Corydalus cornutus) larva, (c) Stonefly (Anacroneuria sp., Perlidae). (d) Stonefly {Anacroneuria sp.) nymph.

lated with two mouthpart types. In the Arctoperlaria, the lobes of the labium are long and flexible and well structured for carnivory; in the Antarctoperlaria, these lobes are reduced, relatively inflexible, and used for chewing plant tissues. (The suborders Filipalpia and Setipalpia, used widely in earlier literature, are no longer recognized as phylogenetically logical subdivisions of the order.)

The immatures resemble the adults, except that they lack wings (fig. 6.4d). They may have conspicuous external filamentous gill tufts ventrally on various parts of the body, vestiges of which remain in adults and are of taxonomic utility. Nymphs of the South American Pelurgo-perla have long, sticky dorsal hairs in which debris becomes entangled, rendering them inconspicuous amid the bottom trash of their habitat.

Except for a few limited studies (lilies 1964), the biology of Latin American stone-flies is not well investigated (Hynes 1976). Most species breed only in cool, running water or cold mountain lakes. Adults are sluggish and often difficult to see when they are at rest on their similarly colored substrata. They fly readily but slowly and feebly.

The Latin American stonefly fauna is fairly extensive and diverse (Benedetto 1974). There are more than 170 species in genera distributed among 7 families Utties 1966, Zwick 1973). Because of their considerable geologic age and significant fossil record, the order offers a wealth of facts for phylogenetic and zoogeographic analysis on a worldwide basis (lilies 1965). The more primitive Antarctoperlaria are mainly austral and exhibit an amphinotic distribution, being found in southern South America as well as in Australia and New Zealand (Eustheniidae, Gripoptery-gidae, Austroperlidae). Diamphipnoidae is restricted entirely to the southern Andes. The arctoperlarian Neonemura illiesi (Noto-nemouridae) is also southern, but its nearest relatives are distributed much like the preceding family and in South Africa (Gondwanaland distribution). These patterns indicate the origin and early diversification of the Plecoptera in Gondwanaland. A few boreal members of this suborder have invaded Latin America, except the West Indies, by way of a southward dispersion from North America. These are certain Perlidae, including the dominant genus Anacroneuria (74 species) (fig. 6.4c), which has moved over the entire continental area, and the genus Amphinemura (Nemouridae), which extends only to central Mexico. General information and literature on the order in Latin America can be found in Baumann (1982), lilies (1977), and Froehlich (1981).

References

Baumann, R. W. 1982. Plecoptera. In S. H. Hurlbert and A. Villalobos Figueroa, eds,, Aquatic biota of Mexico, Central America and the West Indies. San Diego State Univ., San Diego. Pp. 278-279.

Benedetto, L. 1974. Clave para la determinación de los Plecópteros sudamericanos. Stud. Neotrop. Fauna9: 141-170.

Froehlich, C. G. 1981. Plecoptera. In S. H. Hurlbert, G. Rodríguez, and N. Dias dos Santos, eds., Aquatic biota of tropical South America. San Diego State Univ., San Diego. Pp. 86-88.

Hynes, H. B. N. 1976. Biology of the Plecoptera. Ann. Rev. Entomol. 21: 135-153.

Illies, J. 1964. The invertebrate fauna of the Huallaga, a Peruvian tributary of the Amazon River, from the sources down to Tingo Maria. Int. Ver. Limnol. Verh. 15: 1077-1083.

Illies, J. 1965. Phylogeny and zoogeography of the Plecoptera. Ann. Rev. Entomol. 10: 117-140.

Illies, J. 1966. Katalog der rezenten Plecoptera. Das Tierreich 82: i—xxx, 1—632.

Illies, J. 1977. Plecoptera. In S. H. Hurlbert, ed., Biota acuática de sudamérica austral. San Diego State Univ., San Diego. Pp. 185-186.

Zwick, P. 1973. lnsecta: Plecoptera. Phylogenetisches System und Katalog. Das Tierreich 94: i—xxxii, 1—465.

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