Trichoptera Larvae Research Articles

Lake acidity, fish predation, and the distribution and abundance of some littoral insects

Densities of Corixidae (Hemiptera), larval Odonata, and large larval Trichoptera were estimated in the littoral zone of small lakes in an acid-stressed area near Sudbury, Ontario. Fish were present in some lakes and absent in others, and fishless lakes occurred across a wide range of pH. Corixidae were significantly more abundant in lakes without fish than in lakes with fish, and their numbers were not related to the pH of fishless lakes. Anisoptera (Odonata) larvae tended to be more numerous in benthic samples from fishless lakes than from lakes with fish, and their exuviae were significantly more abundant around fishless lakes. In most lakes, the assemblage was dominated by three species; Leucorrhinia glacialis, Libellula julia, and Cordulia shurtleffi. In lakes containing white sucker, Catostomus commersoni, Gomphus spp. were most numerous. In the most acid fishless lakes, L. julia was uncommon, and L. glacialis was extremely abundant. In fishless lakes, numbers of Anisoptera larvae and exuviae were negatively correlated with pH, though species richness was positively correlated with pH. Exuviae of Zygoptera (Odonata) were more abundant around fishless lakes, irrespective of pH. Larvae of Limnephilus (Trichoptera) were most abundant in non-acid fishless lakes, and absent at pH<5.2. Abundances of Banksiola (Trichoptera) were negatively correlated with the pH of fishless lakes.

Effects of sex and reproductive status on the diets of breeding Ring-necked Ducks (Aythya collaris) in north-central Minnesota

We analyzed the diets of 83 Ring-necked Ducks (Aythya collaris) collected on breeding areas in Beltrami County, Minnesota. Larval Trichoptera, Odonata, and Diptera, adult Hirudinea, and seeds from three plant genera, Zizania, Nuphar, and Potamogeton, formed most of the diets of hens during the breeding season. Males differed from females in the amounts and proportions of animal taxa consumed and in their diversity. Differences between the sexes increased during the breeding season. Consumption of animals by females increased significantly between prelaying and laying periods, while consumption by males changed little. We suggest that temporal diet shifts of female Ring-necked Ducks relative to males are a result of the higher protein requirements of females during prelaying and laying periods.

Foraging ecology of blue ducks Hymenolaimus malacorhynchos on a New Zealand river: Implications for conservation

We investigated whether blue ducks Hymenolaimus malacorhynchos preferentially capture prey that have themselves become rare or that need to be present for successful re-establishment. Working at the Manganuiateao River in New Zealand, we measured the densities and relative abundances of benthic invertebrates, numbers of prey fragments in faeces of adult ducks, and foraging behaviour of adult ducks. Invertebrate densities on stones ranged from 3741 m −2 to 14,417 m −2. Stone and boulder communities were dominated by cased caddisfly larvae or Chironomidae larvae in most months. Patterns of apparent selectivity varied, but Trichoptera larvae in the family Hydrobiosidae and in the genus Aoteapsyche (Hydropsychidae) ranked highly, and cased caddis larvae consistently ranked low, in the diet. Discriminant function analysis indicated that apparent prey preferences were partly related to whether foraging blue ducks were gleaning from the tops or undersides of rocks in the river. Canonical correlation analysis showed that ingestion of stonefly and mayfly larvae was associated with diving behaviour, but it was not possible to predict the ingestion of other prey from foraging tactics. No single prey category was so highly valued by the blue ducks we studied that it might limit population establishment at new sites.

Habitat Preference and Seasonal Abundance of Trichoptera Larvae in Ozark Streams, Arkansas

ABSTRACT Trichopterans were collected from both coarse woody debris (CWD) and benthic habitats from three streams in northwest Arkansas from February 1992 through February 1993. Overall density of caddisflies was significantly greater in benthic habitats than on CWD. Trichopteran larvae had significantly greater densities during summer and fall than during winter and spring. Lype diversa was the only species that showed a preference for decay stage and was collected in greatest densities on wood with loose bark or on decayed wood with many interstitial spaces. No species tested showed a preference for volume of biofilm. However, on wood with bark remaining, wood with bark of rough texture produced greater densities of caddisflies than did wood with smooth bark.

Diet of Galemys Pyrenaicus (Geoffroy, 1811 ) in the North of the Iberian Peninsula

In this study data about the trophic ecology of Galemys pyrenaicus in the north of the Iberian peninsula are reported, based on analysis of the digestive tracts of 46 specimens from the Quinto Real mountain range (Navarra). Diet composition, trophic niche width and seasonal variations are described. The total number of prey identified was 2,629. The dict almost completely consisted of aquatic prey. The greater number of prey corresponded to Ephemeroptcra larvae (46.6%), Trichoptera larvae (23.1%), Diptera larvae (13.3%) and Plccoptera larvae (9.0%). Trichoptera larvae provided 56.8% of the biomass, Diptera larvae 17.9% and Ephemcroptera larvae 16.1 %. Galemys pyrenaicus docs not select its prey by size, however a positive selection towards Ephcmeroptera and Trichoptera larvae and a negative one towards Amphipoda was found. The results obtained mean that Galemys pyrenaicus can be characteriscd as a stenophagous species in which energy input is obtained from not-very-mobile invertebrates with a large amount of biomass (Trichoptera larvae), and other small but numerous and accessible taxons (Ephemeroptera larvae).

Long-Term Risk Sensitive Foraging in Rhyacophila nubila (Trichoptera) Larvae from Two Streams

Last instar Rhyachophila nubila larvae captured fast moving mayfly nymphs by ambush hunting from sheltered positions, while sedentary blackfly larvae were captured upon random search. After a trip in a circular aquarium larvae usually returned to the same stone from which they had started. Such «favourite» stones were often, but not always, attached with silk to the bottom by the larvae. The locomotory activity of larvae from two populations peaked during springtime prior to pupation in the field. High locomotory activity was linked to an elevated risk of predation by bullheads. The activity of starved larvae in a poor energetic condition was high relative to that of unstarved larvae. Over the year, larvae from the two populations differed markedly with respect to energy content and activity, and those in a poor condition were most active

Distribution, abundance and development of trichoptera larvae in the river north tyne following the commencement of hydroelectric power generation

AbstractFollowing turbine installation at the Kielder dam, the River North Tyne downstream is now characterized by large daily fluctuations in flow. A survey of trichopteran populations (Hydropsychidae, Rhyacophilidae and Polycentropodidae) was carried out to assess the impact of hydroelectric power generation (Phase III), and to compare the results with similar pre‐impoundment (Phase I) and post‐impoundment (Phase II) surveys. Benthic samples were collected quarterly upstream from the reservoir and at four stations downstream. Although the same three species (Hydropsyche siltalai, Hydropsyche pellucidula and Rhyacophila dorsalis) continue to dominate, there were some notable differences found between sampling sites. Species diversity was drastically reduced at the station nearest the dam, where 99% of all larvae collected were R. dorsalis. At the next station 5 km downstream, where previously H. siltalai had been dominant, R. dorsalis now constitutes 65% of collections. At the two stations farthest away from the dam the former prevalence of H. siltalai was re‐established. It is suggested that the unstable, high flows at the reservoir outlet are likely to favour the predatory R. dorsalis rather than the filter feeding hydropsychids whose nets may be susceptible to damage. Upstream from Kielder Water, R. dorsalis was prominent in benthic samples, whereas numbers of H. siltalai were 10 times lower than in Phase II and 60 times lower than in Phase I. The extent to which such upstream changes may be related to altered patterns of community structure below the dam is not known, but these observations may warrant a more cautious approach when considering upstream areas as unaffected ‘reference sites’. Instar analyses suggested that winter‐warm, summer‐cool discharges were continuing to modify larval growth rates, as noted in Phase II. The results of this study are discussed in relation to present trends in water resource development in Britain, especially with regard to future needs in monitoring and research.

Effect of Substratum Color on Colonization by Macroinvertebraites and Algae in a Boreal Stream

ABSTRACT Black, white and red tiles were used to test the hypothesis of no differences in colonization by macroinvertebrates and algae (expressed as chlorophyll a) on substrata of different colors. Aquatic insects made up 95% of the macroinvertebrates on the tiles. Mean number of insects of the most abundant taxa tended to be greatest on the white tiles. There was a significant effect of color on colonization by Cheumatopsyche (Trichoptera) larvae and total numbers of organisms. There was no interaction between tile position and color on density of aquatic insects. There was no effect of tile color on the quantity of chlorophyll a on the tiles.

The building instinct in Trichoptera larvae

The building instinct in Trichoptera larvae

Diel Feeding Chronology and Diet Selection of Rainbow Trout (Oncorhynchus mykiss) in the Henry's Fork of the Snake River, Idaho

Concurrent rainbow trout (Oncorhynchus mykiss) stomach contents and invertebrate drift samples were collected during three 24-h periods in summer 1987. Feeding was discontinuous through the day on all dates. Mean stomach content weight was minimal after 0400 MST and sharply increased between 1000 and 1200 MST on all three dates. Feeding apparently did not occur after twilight. Mean stomach content weight was correlated with water temperature on two dates and was never correlated with invertebrate drift density for non-age-0 trout. Daily ration (wet weight) was 7% of live weight for non-age-0 trout and 21% for age-0 trout. Trichoptera, Ephemeroptera, and Diptera were most important in the diet; terrestrial insects and aquatic vertebrates were rare. The degree of selectivity varied through 24 h and the interpretation depended on the method of analysis used. Occurrence of low-drift cased Trichoptera larvae in stomachs was correlated with amount of filamentous algae ingested, indicating a degree of epibenthic foraging, although no diel pattern could be reliably discerned. Mean length of prey items in stomachs was larger that the drift in 83% of the samples. Our findings support experimentally derived decision rules-of-thumb for foraging trout: select larger prey items, select vulnerable prey, and relax selectivity when hungry.

Life cycle, production, microdistribution and diet of the damselfly Euphaea decorata (Odonata: Euphaeidae) in a Hong Kong forest stream

Euphaea decorata in Tai Po Kau Forest Stream (Hong Kong) was univoltine. Most recruitment took place in summer, and larval growth proceeded throughout the year. Life‐cycles recorded in 1977–78 and 1978–79 were similar. Annual production estimates, using the removal‐summation, instantaneous growth and size‐frequency methods, were more similar for the 1978–79 generation (ranging from 158.7–174.7; mean 1671 mg dry wt m‐2) than for the 1977–78 generation (93.9‐173‐6; mean 131.7 mg dry wt m‐2). Mean biomass was similar for both generations (ranging from 33.5–33.9 mg dry wt m‐2), and mean P/B ratios were 3.9 1977–78) and 5.0 (1978–79). These are the first estimates of annual production by an Oriental stream insect.Larvae were most abundant at microsites in the middle of the stream. Multiple regression analysis indicated that substratum characteristics were a major determinant of microdistribution. Euphaea decorata apparently favoured poorly‐sorted sediments with highly peaked grain size‐frequency distributions, containing few fine particles.The carnivorous larvae showed ontogenetic changes in diet. Small individuals consumed mainly chironomid (Diptera) larvae; the diet expanded to include (successively) larvae of Ephemeroptera and Trichoptera as E. decorata grew. Seasonal changes in diet were also apparent, although larval diets during spring and summer were similar. There was also considerable overlap between autumn and winter diets. Ontogenetic influences upon prey consumed were not sufficient to account for the observed seasonal differences.

低酸素濃度に対する水生昆虫の呼吸反応

Oxygen is less available in water than in air because of its low solubility and heterogenous distribution. Larvae of Ephemeroptera, Odonata, Plecoptera, Megaloptera, Trichoptera, and aquatic Diptera generally use dissolved oxygen for respiration. In this review, respiratory responses of these aquatic insects to low oxygen conditions are compared in relation to their habitat differences. The species inhabiting relatively low oxygen environments regulate their respiratory rates against hypoxia, but the respiratory rates of riffle-dwelling species are decreased with the decline of oxygen concentration. To compensate respiratory rates, the following are important characteristics : (1) gill development, (2) gill beating, (3) respiratory movement (undulation or ventilation), (4) respiratory pigments (erythrocruorin or haemoglobin), (5) anaerobic metabolism, (6) bimodal breathing (aquatic and aerial respirations), and (7) microhabitat shift. In order to further discuss the speciation processes that produce diverse respiratory characteristics, much more research is needed, especially to find variation in respiratory characteristics within a population or between populations and to examine whether the variation has a genetic basis or not.

Growth and production of filter‐feeding caddis fly (Trichoptera) larvae in a foothill stream in the Soviet far East

The paper deals with some aspects of larval biology in three species of filter‐feeding caddis flies: Stenopsyche marmorata, Arctopsychepalpata and Hydropsyche orientalis inhabiting the foothill river Kedrovaya (Southern Primorye, The Soviet Far East). Data are given on calorific value of wet and dry matter of the various stages. Parameters in equations of dependence of the absolute growth rate upon body weight and size are calculated. Production of larval populations and annual P/B‐coefficients were estimated. Taking into account the calorific value of larval dry matter and ratio of dry/wet weight, the annual production was equal to 56.14 kJ.m‐2 DM for S. marmorata 29.73 kj.m‐2 DM for A. palpata and 9.57 kJ.m‐2 DM for H. orientalis. The annual P/B‐coefficients for the three populations were 2.0,3.6 and 5.8, respectively.

PARASITIC WATER MITE LARVAE (HYDRACHNIDA: HYGROBATOIDEA) ASSOCIATED WITH CADDISFLY LARVAE (TRICHOPTERA: LEPTOCERIDAE, LIMNEPHILIDAE)

AbstractIn the course of benthic sampling during 1981 and 1982 in Lake St. Louis, Que., 28 water mite larvae (Hygrobatidae: Hygrobates) were found parasitizing caddisfly larvae (Leptoceridae: Nectopsyche, Oecetis, Ceraclea). Two other water mite larvae (Unionicolidae: Unionicola) also were found: one on Nectopsyche from Lake St. Louis, and the other on Limnephilus (Limnephilidae) from the Magundy Stream, N.B. Prevalence of parasitism ranged from 8 to 42%. Mite distribution among available hosts suggests host selection by the mites or the absence of mites from certain microhabitats. Parasitism of fully submerged insect larvae by mite larvae represents a further derivation from ancestral behavior patterns. This paper describes five of the seven documented cases of such parasitism on Trichoptera larvae.

Divergent Prey Selection in Two Species of Waterthrushes (Seiurus)

Abstract I studied Louisiana (Seiurus motacilla) and Northern (S. noveboracensis) waterthrushes during an exceptionally dry spring to determine if environmental stress elicited interspecific competition. Previously, I had found little evidence for competition between these species despite wide overlap in foraging methods, use of foraging microhabitats, and characteristics of breeding habitat. I observed breeding adults forage by placing them in a portable flight cage located in natural habitat, and concurrently gathered data on the influence of waterthrush foraging on aquatic invertebrate prey and prey abundance. The species selected different prey. Louisiana Waterthrushes fed predominantly on Trichoptera larvae and on larger average prey than did Northern Waterthrushes, which fed predominantly on Diptera larvae. The species had similar foraging methods and attack rates, indicating that, unlike many Parulinae, their principal foraging differences were in prey selection rather than in means of locating prey. Experiments with foraging exclosures gave no clear evidence that waterthrushes affected prey biomass or composition. There was no significant relation between territory size vs. prey biomass and water cover. No interspecific aggression was observed, and territories overlapped widely, indicating that interference competition did not occur. Divergence in prey selection implies exploitive competition, but invertebrate and habitat data indicate that prey were not limiting, thus making competition for prey unnecessary. Therefore, from these data I cannot eliminate the alternative hypothesis that observed differences between the species may only reflect independent specialization.

Asymmetric Competition for Cases in Agrypnia pagetana (Trichoptera) Larvae

Caseless larvae exposed to different empty cases (short or ordinary length and spiral or stem construction) occupied whichever they first encountered. Later, larvae in short cases left these for ordinary ones. Tactile contacts always preceded any reaction when similar sized larvae met head to head. When both larvae inhabited cases, one larva usually withdrew into its case, while the other moved normally. When a caseless larva encountered a cased one it ran away vigorously, as did both larvae when each was caseless. The possession of a case was crucial to the outcome since alternation of the case (irrespective of type) gave the same result. Case owners were evicted from behind. In most attempts to capture an occupied case, the resident defended its case successfully. Ordinary cases were more often captured than short ones, indicating that short cases are of inferior value. Short case residents often lost their cases, suggesting that these larvae have a low motivation and/or capability for defence. Caseless larvae were preferred by fish, and larvae in short cases were consumed prior to those in ordinary ones. Impaired mobility may limit case length.

The food of Atlantic salmon Salmo salar L. and brown trout Salmo trutta L. smolts during migration in the Orkla river, Norway

Stomach analyses were carried out on 286 Atlantic salmon smolts and 163 brown trout smolts during migration in the river Orkla Central Norway (63°N, 10°E), from 1982 to 1984. Empty stomachs comprised less than 18,4% for salmon and 25,4% for trout. The food composition of both species varied little from year to year. The dominant food items of Atlantic salmon smolts were Trichoptera larvae and nymphs of Plecoptera and Ephemeroptera, each comprising from 17,7 to 31,2 % of the stomach volume. These three insect orders were also the main food of brown trout smolts in addition to Diptera pupae, varying from 17,4% to 32,3% in volume for each food item. The volume of Trichoptera larvae in the smolt stomachs decreased during the migration, while the importance of Ephemeroptera and Plecoptera nymphs as food for the smolts increased. There was a significant overlap in diet between salmon and brown trout smolts both in the different years and during the migration period in 1984.

HIGH-DOSAGE TREATMENT OF A QUEBEC STREAM WITH BACILLUS THURINGIENSIS SEROVAR. ISRAELENSIS: EFFICACY AGAINST BLACK FLY LARVAE (DIPTERA: SIMULIIDAE) AND IMPACT ON NON-TARGET INSECTS

AbstractA typical lake outlet of the Canadian Shield was treated for 15 min with a high dose (5.28 g/L s−1 of discharge) of Teknar®, a commercial formulation of Bacillus thuringiensis serovar. israelensis. Efficacy on Simuliidae larvae and impact on non-target aquatic insects of this stream were monitored using drift nets, counting plates, and artificial turf substrates along a 1000-m section downstream of the site of application. Compared with a 4-day pre-treatment average for 12-h sampling periods, drift of Simuliidae increased from 64 to 92 ×, with shorter peaks of 133–184 ×, 2–6 h after treatment. There was no evident drift increase in larvae of Ephemeroptera, Plecoptera, Trichoptera, Chironomidae, or dipterous pupae, but larvae of Blephariceridae (Diptera) were severely affected as their drift was increased by up to 50 × and remained high for 3 days. After 30 h the mortality of Simuliidae on counting plates ranged from 95 to 82% in the first 300 m, with detachment rates of 78.5–46.5%. Densities of non-target insect larvae were not reduced on the artificial substrates, except for 2 genera of Chironomidae (Eukiefferella and Polypedilum) which were reduced 26 to 39% of their original density. Drifting larvae of 1 chironomid genus (Phaenopsectra) also showed symptoms of toxemia by B.t.i. The main impact of the treatment was thus seen in 2 Nematocera families (Chironomidae and Blephariceridae) which were mainly exposed to B.t.i. sedimented on the bottom of the stream or attached to periphyton growing on rocks.

Microhabitats of stream invertebrates on two submersed macrophytes with contrasting leaf morphology

Larvae of Chironomidae, Simuliidae and Trichoptera exhibited various patterns of micro‐distribution on the submersed macrophytes Potamogeton×zizii, with broad leaves, and P. pectinatus, with thread‐like leaves. Seven common species of chironomid, six belonging to the subfamily Orthocladiinae and one to the Chironominae, showed four distinguishable patterns of distribution. The density of Simulium larvae was much greater towards the apices of the stems on both plants. Among three species of Trichoptera studied, the predatory Rhyacophila dorsalis had a pattern of distribution which was strongly related to prey density, particularly that of Simulium, on P. ×zizii, but not on P. pectinatus. P. ×zizii supported proportionately more free‐ranging scrapers, such as the chironomid Thienemanniella vittata. than did P. pectinatus while the reverse was true for filter‐feeders. These patterns are discussed in relation to habitat structure and behavioural characteristics.

TOXICITY OF BACILLUS THURINGIENSIS VAR. KURSTAKI TO AQUATIC INSECTS

AbstractRepresentative aquatic insects, larvae of Simuliidae, Chironomidae, Trichoptera, Megaloptera, and nymphs of Ephemeroptera and Plecoptera, were tested for susceptibility to continuous exposure to Bacillus thuringiensis Berliner var. kurstaki at 4.3, 43, and 430 IU/mL. Only Simulium vittatum was affected, and at the highest concentration. Effects on other organisms, particularly Prosimulium fuscum/mixtum, were suggested. The lowest of the concentrations tested was twice the worst-case transitory concentration peaks expected in water from aerial forest spraying at 30 BIU/ha. Spray buffer zones around water bodies are unnecessary at this spray rate.