Dietary variations of predaceous caddisfly larvae (Trichoptera: Rhyacophilidae,Polycentropodidae and Arctopsychidae) from British Columbian streams

The diets of larval Rhyacophilidae (Rhyacophila inculta), Polycentropodidae (Polycentropus variegatus) and Arctopsychidae (Parapsyche almota and P. elsis) from five streams in the University of British Columbia Research Forest, British Columbia (Canada), are recorded and related to feeding mode/constructional activities and prey representation in the habitat. Particular attention was paid to the extent of dietary overlap and the degree of intraspecific dietary variations between streams. An overall similarity of the diets of the study species was notable and all commonly consumed chironomid (Diptera) larvae, Simulium (Diptera) and Zapada (Plecoptera), although there was interspecific variation in the relative importance of these items. Polycentropus variegatus and Parapsyche spp. ate Baetis and Paraleptophlebia, the latter predators also consuming Hydrachnellae (Acarina). Other prey were generally of minor importance and consequently interspecific dietary overlaps were high. Differences in the range of prey consumed by predaceous Trichoptera were apparent. Free-foraging R. inculta which selectively consumed sedentary simuliid larvae had the narrowest niche breadth. Parapsyche spp. and Polycentropus variegatus foreguts generally contained an over-representation of chironomid larvae compared to their proportionate occurrence in the benthos, and these caddisflies exhibited high niche overlap. The relative importance of chironomids as food for Parapsyche spp. and Polycentropus variegatus is attributed to prey behaviour, i.e. drift, and poorly developed escape responses when they are caught on the predator's net.     

毛翅目化石研究进展

本文详细总结和回顾了世界毛翅目化石研究简史,列出已发表的化石种类名录、分布及年代,共37科、193属、661种(包括中国发现的4科9属15种),描述了不同地质时期主要毛翅目化石的分类单元和分布地区。简要介绍了毛翅目分类系统及系统发育、不同地质时期毛翅目化石的产地及时代。初步分析了目前该类群所存在的一些问题,并对今后的研究工作进行了展望。     

Microhabitat type selection of caddisfly larvae (Insecta: Trichoptera) in a shallow lowland stream

The relationship between caddisfly assemblage structure and four selected environmental variables (substrate, water depth, flow type and amount of the coarse particulate organic matter) was investigated in a Slovenian lowland stream. Caddisflies were sampled at four stream reaches according to selected microhabitat types. All together, 168 quantitative samples were taken at 21 sampling points between October 1998 and July 1999. Of 48 collected species, 30 were included in the analysis. Significant correlation was observed between species and environmental variables. As a complement to a CCA biplot representation, species assemblages within the community were also determined using cluster analysis. Nine groups and subgroups were established. Most caddisfly species prefer coarse substrate in shallow water (5–10 cm) with chute water flow, whereas few species were found on fine substrate in deep water. A significant positive correlation was found between mean substrate size and total number of species, and between indices of species richness and diversity, whereas depth did not show any correlation with these parameters. Seven species were found mostly in marginal habitats, whereas four (Potamophylax rotundipennis, Anabolia furcata, Athripsodes bilineatus and Lithax obscurus) did not show any strong preferences for selected parameters. In addition, habitat preferences were associated with the feeding types of the caddis larvae.     

Structures on the antennal flagellum of a caddisfly,frenesia missa (Trichoptera,Limnephilidae)

Non-innervated macrotrichia and microtrichia, thick-walled chemoreceptors and three kinds of thin-walled chemoreceptors are present on the antennal flagellum of Frenesia missa. One of the thin-walled receptors, the plate organ, is of a type not previously recorded for any insect. About four times as many plate organs are present on the flagellum of the male as on that of the female. They occur also on the maxillary and labial palps.     

The caddisfly fauna (Trichoptera) of Russia: on the centenary of exploration

A brief overview of the history of faunistic studies in Russia during the past century is presented. The existence of 643 species of 148 genera (28 families) is reported according to the results of the long-term investigation of the Russian fauna of the Trichoptera. There are 4 regional faunas of Trichoptera in Russia: Boreal European, Caucasian, Siberian, and Far Eastern. The tasks and prospects of the future studies are considered.     

一种毛翅目昆虫的生态治理研究

针对生活在水流速度较快的湖南省柘溪水电站一带河床大量发生的原双栖纹石蛾(Amphipsyche proluta)来说采用一般的防治措施都很难付诸实施,或者只能是治标,不能治本。经1997年至2000年的调查研究和试验分析得知人为去掉河底大型石块,加深河水深度,减缓流速,以破坏适宜于该石蛾幼虫生存的生态环境,引进生态致死因子,是从根本上杜绝该石蛾发生的较为理想的办法。     

Substratum preference of the caddisfly Helicopsyche borealis (Hagen) (Trichoptera: Helicopsychidae)

The position of Helicopsyche borealis (Hagen) (Trichoptera: Helicopsychidae) larvae on the substratum surface is dependent on the current regime but varies with larval size. All size classes of larvae chose significantly different positions on the substratum under high versus low current velocities. All size classes preferred exposed surfaces under low current velocities. Small larvae preferred the upper surfaces of substrata under low current velocities and were physically displaced under high current velocities. Larger larvae also occurred on upper surfaces, but were more evenly dispersed over all surfaces than smaller larvae, and tended to aggregate on down-stream faces of rocks during high flow.     

Revision and synopsis of the caddisfly genus Dicosmoecus (Trichoptera: Limnephilidae; Dicosmoecinae)

Six species of Dicosmoecus are recognized: the palatus species group of Siberia and Japan [palatus (McL.), obscuripennis Banks, and jozankeanus Mats.)]; and the atripes species group of western montane North America [atripes (Hagen), gilvipes (Hagen), and pallicornis Banks]. D. obscuripennis is re‐established as a valid species distinct from palalus and recorded from the Yukon Territory and Alaska, and also Siberia. Keys are provided for identification of males, females, and larvae. Hypotheses of phylogeny and biogeography are proposed, stating that the palatus and atripes species groups evolved independently in Asia and North America respectively; and that obscuripennis of the palatus group extended its range to North America during the Pleistocene Beringian land connection between the two continents.

Data on food, life cycle, habitat, and distribution are given for the North American species. Most Dicosmoecus appear to be generalized predator‐shredders with robust, toothed mandibles; but fifth instar larvae of D. gilvipes feed mainly by scraping rocks for diatoms, a behaviour which is evidently responsible for eroding the slender blade and weakly formed teeth of the mandible, unique to this species, to a uniform scraping edge. D. gilvipes is further distinctive in usually having a 1‐year life cycle, whereas atripes and the other North American species usually have a life cycle of 2 years.     

The identification of British limnephilid larvae (Trichoptera)

Fifty–six species of Limnephilidae have been recorded from Britain. Larvae of forty–three species were collected, and the identities of forty–two were confirmed by direct association of individual larvae with their resultant adult stage. Information was obtained on the larvae of twelve more species, leaving the larva of only onespecies, Limnephilus fuscinervis, unknown. A key is provided to the fifth instar larvae of fifty–four species. Limnephilus nigriceps is omitted from the keydue to lack of information. The terminology of morphological characters is reviewed.     

Isolation and characterization of microsatellite markers in the caddisfly Drusus discolor (Trichoptera: Limnephilidae)

We describe the development of and amplification conditions for microsatellite primers isolated from the caddisfly Drusus discolor. Eight polymorphic microsatellite loci were developed and screened for variability using 37 individuals from two populations from central Europe. The primers yielded an average of 8.6 alleles per loci. No linkage disequilibrium between loci was detected, while three loci showed deviations from Hardy–Weinberg equilibrium in one of the two tested populations.     

The roles of dispersal limitation and environmental conditions in controlling caddisfly (Trichoptera) assemblages

1. Many recent studies have quantified the relative importance of environmental variables and dispersal limitations in shaping the structure of stream communities. However, the relative importance of these factors at different spatial extents has been seldom evaluated. 2. We analysed the distribution of caddisfly species in 89 Amazonian streams in relation to stream characteristics and spatial variables representing overland dispersal routes. The streams occur in three regions that differ in spatial extent and environmental characteristics. We analysed the data using partial redundancy analysis with two predictor data sets, one environmental and one spatial, to evaluate the variation in assemblage composition. We also separated caddisflies into ‘good’ and ‘poor’ dispersers to evaluate possible differences in the responses of these two groups. 3. The environmental component explained a higher proportion of variance in assemblage composition than did the spatial component. Spatial effects were evident only when data from all three regions were analysed together, although the exclusive spatial fraction was quite low. Good dispersers responded similarly to the community as a whole, while poor dispersers were related to environmental variables only in one region and also were not related to spatial variables. 4. Caddisflies were most affected by environmental factors. The large environmental effect and small spatial effect are in accord with the use of these stream insects as good indicators of site properties and disturbances in monitoring programmes.     

Effects of Pacific salmon spawning and carcass availability on the caddisfly Ecclisomyia conspersa (Trichoptera: Limnephilidae)

1. The effects of spawning coho (Oncorhynchus kisutch) and chum salmon (Oncorhynchus keta) on the limnephilid caddisfly Ecclisomyia conspersa were evaluated by experimentally excluding salmon from the upper 14‐m stretch of a spawning channel by a wire‐meshed fence. Density, and development and growth rates, of larvae upstream of the fence (without salmon) were compared with those downstream (with salmon). 2. Larval density in the stretch with salmon declined during spawning, but increased again after spawning subsided and the carcasses of dead fish became available. In the stretch with salmon, larval density on salmon carcasses was seven to 37 times greater than on the adjacent channel substratum. The rate of larval development in the stretch with salmon was greater than that in the stretch without salmon. Two months after carcasses became available, 98% of larvae sampled from the stretch with salmon were in the fifth instar, compared to only 23% from the stretch without salmon. Body weight of E. conspersa in the stretches with and without salmon increased by an average of 3.04 and 2.38 mg, respectively, over a 6‐month period. 3. ¹⁵N values of larvae from the stretch with salmon increased following the arrival of the fish, suggesting that the larvae were feeding on salmon‐derived material, such as eggs and carcasses, which contain a high proportion of the heavier stable isotope. In contrast, ¹⁵N values of larvae from the stretch without salmon remained relatively constant throughout the experiment. The availability of salmon carcasses as a high‐quality food source late in larval development may increase survival and fecundity of E. conspersa. 4. These substantial differences were consistent with the view that they were due to the experimental exclusion of salmon and salmon carcasses from the upstream stretch, though the study was un‐replicated and thus precludes ascribing causation more definitely.     

Exploration of the utility of fluctuating asymmetry as an indicator of river condition using larvae of the caddisfly Hydropsyche morosa (Trichoptera: Hydropsychidae)

Organisms are subject to three types of morphological asymmetry: Directional Asymmetry, Antiasymmetry and Fluctuating Asymmetry, but only the latter (FA) is related to the environmental stress acting upon individuals during their development. Larvae of Hydropsyche morosa from five rivers in Ontario, Canada, each exhibiting different degrees of human impact, were examined for FA. Specimens were obtained from collections in the Royal Ontario Museum dating back to 1951, and from fresh collections to 1999. Twelve morphological characters were assessed on both the left and right sides of 297 larvae, and eight of them demonstrated FA. There was a tendency to increase the levels of FA over time. Levels of nitrogen, conductivity and chloride in the river water, used as an index of pollution, were significantly and positively correlated with increasing incidence of FA in four of the characters, the remainder were independent of pollution.     

Swarming patterns of light trapped individuals of caddisfly species (Trichoptera) in Central Europe

This study is on the light trapping of caddisfly species (Insecta: Trichoptera) related to the proportion of males and females and the moon phases. The data collected includes 24 species in 9 light-trap stations, for 49 swarming events between the years 1980 and 2000. We found the massive emergence of adults happens fractionally in swarming intervals. This is connected with the phenology and life cycle of each species. The percentage of males and females of the same species during different swarming events cannot be considered equal. The proportion of males and females are different in the swarming of different species. We found that the number of male and female individuals is substantially synchronized with each other within the swarming, but it can be different in the case of each species. The duration of the swarming, even in the same species, are not always uniform. The effect of the Moon cannot be clearly identified in any species, even if data from several swarmings are available. The swarming peaks appear near different Moon quarters.     

Further revision of the caddisfly family Uenoidae (Trichoptera): evidence for inclusion of Neophylacinae and Thremmatidae

Abstract. A survey of characters within the Limnephilidae was made to test the cladistic hypothesis underlying traditional classification placing Neophylacinae as a subfamily of the Limnephilidae. Characters emerged which support an alternative hypothesis of phylogeny and classification, linking the Neophylacinae with the Thremmatidae and with the Uenoidae. The Uenoidae as defined here contain two monophyletic groups: subfamily Uenoinae containing the four genera Uenoa, Sericostriata, Neothremma and Farula previously constituting Uenoidae ( sensu Wiggins et al. , 1985), and subfamily Thremmatinae consisting of Thremma, Neophylax and Oligophlebodes. The new classification is shown to have predictive value for behaviour and ecology of the taxa.     

The diet activity patterns of caddis larvae (Trichoptera)

Larvae of Potamophylax cingulmus (Stephens), Drusus annulatus Stephens, and Odontocerum albicorne (Scopoli) showed a nocturnal periodicity in their activity pattern, whereas larvae of Anabolia nervosa (Curtis) showed a diurnal periodicity. Both periodicities appeared to be controlled solely exogenously—by a direct response to current light intensity.     

Caddis larvae (Trichoptera) as predators of fish eggs

SUMMARY. Eggs of bullhead ( Cottus gobio ) were found with damaged shells and with the contents removed. Experiments in laboratory aquaria indicated that the damage was caused by caddis larvae and that the type of caddis involved in egg predation might be identified by the nature of the shell damage.     

Reach-scale distribution dynamics of a grazing stream insect, Micrasema quadriloba Martynov (Brachycentridae, Trichoptera), in relation to current velocity and periphyton abundance

Reach-scale temporal shifts in the distribution of larvae of a grazing caddisfly, Micrasema quadriloba (Brachycentridae), were investigated in a Japanese mountain stream. The larvae showed an aggregated distribution within the reach at the beginning of the immigration, then became randomly dispersed throughout the reach as the immigration progressed. The abundance of periphyton in the reach decreased dramatically with increasing dispersal of the larvae. Simple regression analyses revealed that the stream's flow regime was the most important environmental factor that determined the reach-scale distribution of the larvae and that the relationship between the flow regime and the distribution of the larvae shifted temporally. In addition, our results suggest that only this species of grazing insect, which was dominant in the study reach, controlled the reach-scale abundance of the periphyton.