Aquatic Orders

Aquatic insect life in Latin America is diverse and abundant in both running and standing inland waters and, to a limited extent, in the seas surrounding the continental and island areas (see Ecosystems, chap. 2). All the major categories of water-dwelling insects are represented and widely distributed except in the nutrient-poor black water and clear water systems. Relative to those carrying white waters, the major black water drainages of the Guiana (e.g., Rio Negro) and Brazilian (e.g., Rio Tapajos) shields of South America are well known as faunistically depauperate ("hungry rivers") with regard to insects as well as vertebrates (Junk and Furch 1985: 15). Amazonia is still largely unexplored with respect to aquatic insects, as is most of the Andes. Many taxa found in streams in the southern portion of South America are very ancient and show affinities to Lhe faunas of the Australian region and southern Africa (Gondwanaland and amphinotic distributions) (lilies 1969).

Families of insects in mostly terrestrial orders that have adapted to life in fresh water are discussed elsewhere (see water bugs, chap. 8; water beetles, chap. 9; ; water midges, punkies, mosquitoes, etc., chap. 11). Those orders totally adapted to life in fresh water are the subject of this chapter.

Two of these orders, the Ephemer-Optera and Odonata, form the Paleoptera, considered to be the stem group and the Host ancient of the winged insects, from j hich all higher insects evolved. Evidence for this comes partly from the lack of a flexing mechanism in the wing articulation and the reliance of the immatures on gills for respiration, not atmospheric air, the latter being a secondary adaptation in aquatic insects. Possibly the most primitive of the Neoptera are the Plecoptera, as indicated by their generalized body structure. The Megaloptera and Trichoptera are higher Neoptera but are thought to occupy positions basal to the phylogeny of the neuropteroid and panorpoid orders for the same reasons (see Evolution and Classification, chap. 1).

The larvae and nymphs (sometimes called naiads) of these orders inhabit waters of all descriptions, including saline and thermal waters, buL none are marine as are some species of the aquatic families discussed elsewhere. They are active but remain within the boundaries of their vastly varied microhabitats. Dobsonfly and caddis fly pupae are submerged, often in protective cases or cocoons, but may be terrestrial and even active, having functional muscles for movement of legs and mouthparts. The adults remain close by the habitats of the immatures and are mostly predaceous or do not feed.

Current and comprehensive introductions to the biology and zoogeography of Latin American aquatic insects, including extensive literature citations, are to be found in an important three-parL collaborative treatment edited by Hurlbert and others (1977, 1981, 1982); for important treatments of local faunas, see also Vanzo-

lini (1964) for Brazil only and Roldán (1988) for Colombia.

References

Hurlbert, S. H. ed. 1977. Biota acuática de sudamérica austral. San Diego State Univ., San Diego.

Hurlbert, S. H., G. Rodríguez, and N. Dias dos Santos, eds. 1981. Aquatic biota of tropical South America. Pt 1. Arthropoda. San Diego State Univ., San Diego.

Hurlbert, S. H., and A. Villalobos Figue-roa, eds. 1982. Aquatic biota of Mexico, Central America and the West Indies. San Diego State Univ., San Diego.

Illies, J. 1969. Biogeography and ecology of Neotropical freshwater insects, especially those from running waters, hi E. J. Fittkau, J. Illies, H. Klinge, G. H. Schwabe, and H. Sioli, eds., Biogeography and ecology in South America. 2: 685-708. Junk, The Hague.

Junk, W. J., and K. Furch. 1985. The physical and chemical properties of Amazonian waters and the relationships with the biota. In G. T. Prance and T. E. Lovejoy, Amazonia. Pergamon, Oxford. Pp. 3—17.

Roldan, G. 1988. Guía para el estudio de los macroinvertebrados acuáticos del Departamento de Antioquia. Fondo Fen Colombia/ COLCIENCIAS, Univ. Antioquia, Bogotá.

Vanzolini, P. E., ed. 1964. Historia natural de organismos aquáticos do Brasil: Bibliografía comentada. Fund. Amparo Pesq. Est. Sao Paulo, Sáo Paulo.

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