The feeding relationships of two invertebrate predators in a New Zealand river

Abstract

SununaryThe size frequency distributions and foods of the larvae of Archichatdlodes diversus (Megaloptera: Corydalidae) and Stenoperia prasina {Plecoptera: Eustheniidae) were studied for a year in the Glenttd River, South Island, New Zealand. These two species are the largest invertebrate predators inhabiting .streams and rivers in New Zealand, where they are the only carnivorous members of their respective orders. Both species occttpied the same habitat with A. diversus being slightly more abundant in most months. Many small larvae occurred within the sediments of the stream bed, whereas more larger larvae were found on stones lying on the surface. A wide size range of larvae was present throughout the year and the median size (in terms of head width) of hoth .species was similar in most months. Larval growth could not be determined from field data and the life cycles of both species can be described as non-seasonal. Quantitative sampling in 5 months provided estimates of population densities. These were maximal in December when valties of 1361 m'^ for ^-diversus and UAjm^for S. prasina were obtained. Larval Chironomidae and mayflies of the genus Deleatidium were the most frequently taken prey of both predators in all months, and no strong relationship between size or species of predator and size of prey was found. Caseless trichopteran larvae formed a less important component of the diets of both species and detritus was ingested by some individuals. No instances of cannibalism and only one example of crosspredation by each predator was seen. Diel sampling inNovember showed that large Deleatidium larvae were relatively more abtmdant in the guts of insect predators attd in nocturnal drift samples than in the benthos. This st4ggests that tbeir greater activity at night may increase their susceptibility to predation by nocturnal feeders.No clear ecological segregation of the two species with respect to habitat or prey utilization was found and there was no obviotis interspecific competition for food, which appeared to be abundant at all times. Finally, the prevalence of non-seasonal life cycles in New Zealand aquatic insects is discussed in relation to the low degree of speciation in several grottps.

Feeding ecology of three predacious aquatic insects and two fish in a riffle of the Speed River, Ontario

“…Moreover, because N. serricornis fed primarily on philopotamids and polycentropodids while R. atratulus fed on hydropsychids, the extent of diet overlap between these two predators is even lower than is suggested by the overlap figure. We suggest that there is partitioning of prey resources by these predators. Few studies of predacious aquatic insects have gone beyond a single taxonomic order (exceptions are Devonport and Winterbourn, 1976;Hildrew and Townsend, 1976) and therefore comparisons have not been made between predator morphologies and foraging behavior among different insect orders. Investigations of stoneflies have shown that predator size may be more important than species differences, since small perlodid stoneflies have diets that are similar to smaller size classes of other, large predacious stoneflies (e.g., Isoperla filva versus Classenia sabulosa by Fuller andStewart, 1977, 1979).…”

“…The fish studies can be further divided into investigations of single species (usually associated with fish life histories) or more commonly, of coexisting species; the latter investigations usually examine diets of congeners (e.g., Adamson and Wissing, 1977;Allan, 1978), or may characterize diets of entire fish communities (Zaret and Rand, 1971;Johnson and Johnson, 1982). Studies on the food habits of predacious macroinvertebrate predators are similar in scope and design to the fish studies, ranging from individual species to studies of co-occurring predators in a stream community (Tartar and Krumholz, 1971;Stewart et al, 1973;Winterbourn, 1974;Devonport and Winterbourn, 1976;Hildrew and Townsend, 1976;Seigfried and Knight, 1976;Fuller andStewart, 1977, 1979;Kovalak, 1978;Allan, 1982;Johnson, 1981Johnson, , 1983. These studies provide a wealth of information on what is eaten by different species and often give some information on prey selection or avoidance, usually based on comparisons of diet composition with samples of prey availability.…”

Comparison of the macroinvertebrate faunas of runs and riffles in three New Zealand streams

“…Coloburiscus, Nesameletus (Ephemeroptera); Stenoperla, Zelandoperla, Zelandobius (Plecoptera); Hydrobiosis, Psilochorema, Pycnocentria, Olinga, Aoteapsyche (Trichoptera); Archichauloides (Megaloptera); Potamopyrgus (Gastropoda) . This similarity arises largely because many New Zealand aquatic insects have broad habitat requirements , show little evidence of food specialisation (Winterbourn 1974(Winterbourn , 1978aCrosby 1975;Devonport & Winterbourn 1976;Davis & Winterbourn 1977;Cowie 1980), and possess flexible, poorly synchronised life histories (Winterbourn 1978b;Cowie 1980;Towns 1981Towns , 1983. In the three streams we studied, virtually all of the above genera were present, and species lists for the streams were remarkably similar.…”

Trout predation and the size composition of stream drift 1

“…A shift from daytime to nighttime drifting within a taxon has been reported for B. bicaudatus (this study), P. haterale cited above, DeZeatidium sp. (Ephemeroptera) (Devonport and Winterbourn 1976), Amiocentrus aspilus (Trichoptera) (Anderson 1967), HeZicops yche borealis and some Limnephilidae (Bishop and Hynes 1969).…”