Management Implications

It is evident from the foregoing discussion that disturbance in the riparian zone will ultimately affect the large and varied group of aquatic insects present in any reasonably healthy stream or lake. Aquatic insects have intricate life cycles which if interrupted at any point may mean the disappearance or reduction of a given species in a given area. While many insects have life cycles with great flexibility, enabling them to respond to environmental conditions, i.e. diapause which delays development of an egg, larva, pupa, or adult until conditions are favorable, it must be remembered that such flexibility has evolved over long periods in response to gradually changing conditions. Such activities as channeling streams, logging, building dams, grazing livestock, drawing water out of streams, and putting in riprap have the potential for sudden interference with life cycles.

Dams are so disruptive to all stream life that there is no point in discussing them in this context. The effects of logging on stream life are being considered elsewhere (Mahoney and Erman 1981).

An insect that needs soil along a bank for a pupation chamber will not find it in a channelized stream or one with riprapped banks. Larvae that must immediately drop into water upon hatching may be eliminated if vegetation is destroyed because adults will not find suitable egg-laying sites. It is worth noting that Desmonabethula , the first caddisfly larva known to migrate daily from the water to feed, was found in a study area where grazing has been eliminated for many years. Its habitat, springstream in peatlands, is also a favorite of livestock in the Sierra Nevada. It may be no coincidence that these larvae have never been reported from any other area.

The more we know about life cycles, behavior, and feeding habits of individual species of aquatic insects, the more accurate can be our predictions on the effects of changes in the riparian zone. It is already clear that the riparian zone and aquatic insects are connected in an inseparable and intricate web of relationships.