Respiratory behaviour of larvae of four species of the Family Polycentropodidae (Trichoptera)

Larvae of Plectrocnemia conspersa and Polycentropus flavomaculatus from flowing water and Cyrnus flavidus and Holocentropus picicornis from still water were selected for study. In the above sequence, these larvae are associated with increasing ranges of temperature in their natural habitats. Experimental determination of lethal temperatures and investigations on ventilation frequency indicated that the larvae were increasingly tolerant of temperature in the same sequence of species. C. flavidus and H. picicornis showed infrequent ventilation which was little affected over wide ranges of temperature and dissolved oxygen but was stimulated erratically by water flow. P. conspersa and P. flavomaculatus showed more active ventilation which was more sensitive to changes in temperature and dissolved oxygen and was decreased by water flow. Consideration of ventilation in relation to oxygen uptake in P. conspersa and P. flavomaculatus suggests that ventilation activity may account for some 60–70% of active oxygen uptake. Differences in ventilation behaviour may thus be important in limiting larval distribution in stream systems.     

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.     

Twenty-four new species of Polycentropus (Trichoptera, Polycentropodidae) from Brazil

Twenty-four new species of the caddisfly genus Polycentropus (Insecta: Trichoptera: Polycentropodidae) occurring in Brazil are diagnosed, described, and the male genitalia of each are illustrated. Eighteen of the new species are placed in the Polycentropus jorgenseni species complex of the Polycentropus gertschi group of New World Polycentropussensu lato. Furthermore, 6 new species within the Polycentropus gertschi group (Polycentropus ancistrussp. n., Polycentropus boraceiasp. n., Polycentropus cariocasp. n., Polycentropus froehlichisp. n., Polycentropus galharadasp. n., and Polycentropus graciosasp. n.) are placed in an informal diagnostic cluster of species with Polycentropus urubici Holzenthal and Almeida. Ten of the other Polycentropus gertschi group species form a second cluster of diagnostically similar species, the Polycentropus soniae cluster (Polycentropus caaetesp. n., Polycentropus carolaesp. n., Polycentropus cheliceratussp. n., Polycentropus fluminensissp. n., Polycentropus itatiaiasp. n., Polycentropus minerosp. n., Polycentropus santateresaesp. n., Polycentropus soniaesp. n., Polycentropus tripuisp. n., and Polycentropus virginiaesp. n.). Two of the remaining 8 new species are included in the Polycentropus jorgenseni species complex (Polycentropus cipoensissp. n. and Polycentropus verruculussp. n.), while the remaining 6 are unique and cannot be placed in one of the groups at this time (Polycentropus acinaciformissp. n., Polycentropus amphirhamphussp. n., Polycentropus cachoeirasp. n., Polycentropus inusitatussp. n., Polycentropus paprockiisp. n. and Polycentropus rosalysaesp. n.).     

A New Species of Plectrocnemia from Sicily (Trichoptera,Polycentropodidae)

Plectrocnemia alicatai sp.n. from Sicily (Nebrodi Mountains) is described and figured from the adult male.     

New species of Plectrocnemia and Nyctiophylax (Trichoptera, Polycentropodidae) from China

Four new species of genus Plectrocnemia and 4 new species of genus Nyctiophylax are described, namely: Plectrocnemia verticalissp. n.; Plectrocnemia acuminatasp. n.; Plectrocnemia cryptoparameresp. n.; Plectrocnemia qianshanensissp. n.; Nyctiophylax (Nyctiophylax) senticosussp. n.; Nyctiophylax (Paranyctiophylax) gracilissp. n.; Nyctiophylax (Paranyctiophylax) pungenssp. n.; and Nyctiophylax (Paranyctiophylax) auriculatussp. n.     

Twenty-one new Polyplectropus species from New Caledonia (Trichoptera: Polycentropodidae)

Twenty-one new Polycentropodidae (Trichoptera) species are described: Polyplectropus aberrus, P. dorsospinus, P. nodyg, P. yndog, P. clavus, P. nathalae, P. millei, P. christinae, P. koueus, P. viklundi, P. hovmoelleri, P. aoupiniensis, P. tenerus, P. angustus, P. curvispinus, P. caledonia, P. piroguensis, P. triangulatus, P. pernodensis, P. taoensis, and P. papei spp. novae, representing the first species records of this family from New Caledonia. A key to males of the New Caledonian Polycentropodidae is provided, and distribution maps are presented for all species.     

The genus Plectrocnemia Stephens of Japan (Trichoptera; Polycentropodidae)

The Japanese species of the genus Plectrocnemia Stephens (Trichoptera; Polycentropodidae) are revised based on examination of male material. Five new species are described: P. divisa, P. suzukii, P. corna, P. scoparia, and P. odamiyamensis. P. levanidovae Vshivkova et al. is recorded from Japan for the first time and redescribed. P. wui (Ulmer), P. tochimotoi Schmid, P. tsukuiensis (Kobayashi), and P. okiensis Kobayashi are redescribed. Arctopsyche hirayamai Matsumura is transferred to Plectrocnemia and redescribed. P. asuana Kobayashi, P. kadowakii Kobayashi, and P. makiensis Kobayashi are transferred to the genus Nyctiophylax Brauer.     

A revised key to larvae of the genus Plectrocnemia (Polycentropodidae: Trichoptera) in Britain, with notes on Plectrocnemia brevis McLachlan

SUMMARY. The key distinguishes the previously unknown larva of Plectrocnemia brevis McLachlan from larvae of the other two British Plectrocnemia species, P. conspersa (Curtis) and P. geniculata McLachlan. Notes are given on the larval habitat, life cycle and identification of the adult of P. brevis.     

Influence of velocity and food availability on catchnet dimensions of Neureclipsis bimaculata (Trichoptera: Polycentropodidae)

Larvae of Neureclipsis bimaculata (Trichoptera: Polycentropodidae) construct elaborate catchnets in lotic habitats to trap small drifting invertebrate prey. Three populations located at two oligotrophic and one eutrophic site were studied in southern Sweden. Measurements were made of larval weight, net size, seston quality and quantity, and stream velocity.
Neureclipsis larvae alter their net dimensions in response to both velocity and seston concentration. This was determined by comparing net structure and seston at the three locations. Larvae from the eutrophic, high quality seston site attain a significantly (P < 0.001) heavier instar V dry weight, spin a smaller catchnet, filter a volume of water dependent on body size, and slightly alter their catchnet dimensions with velocity. Larvae from the two oligothrophic sites are significantly smaller than those from the eutrophic site, spin a larger net at comparable velocities, filter a larger volume of water at comparable weights, and alter net dimensions with velocity.
Estimates of silk production indicate that the net cost is minimized by spinning a very fine silken strand and by adding silk over a period of time. The cost while large is offset by a large capture rate of prey.
The structure of Neureclipsis nets appears to be the result of a trade-off between maximizing food capture and minimizing hydraulic stress on the net.     

Ontogenetic shifts in the functional response and interference interactions of Rhyacophila dorsalis larvae (Trichoptera)

1. Ontogenetic shifts in predator behaviour can affect the assessment of food‐web structure and the development of predator–prey models. Therefore, it is important to establish if the functional response and interference interactions differ between life‐stages. These hypotheses were tested by (i) comparing the functional response of second, third, fourth and fifth larval instars of Rhyacophila dorsalis, using three stream tanks with one Rhyacophila larva per tank and one of 10 prey densities between 20 and 200 larvae of Chironomus sp.; (ii) using other experiments to assess interference within instars (two to five larvae of the same instar per tank), and between pairs of different instars (one, two or three larvae per instar; total predator densities of two, four or six larvae per tank). 2. The first hypothesis was supported. The number of prey eaten by each instar increased with prey density, the relationship being described by a type II model. The curvilinear response was stronger for fourth and fifth instars than for second and third instars. Mean handling time did not change significantly with prey density, and increased with decreasing instar number from 169 s for fifth instars to 200 s for second instars. Attack rate decreased progressively with decreasing instar number. Handling time varied considerably for each predator–prey encounter, but was normally distributed for each predator instar. Variations in attack rate and handling time were related to differences in activity between instars, fourth and fifth instars being more active and aggressive than second and third instars, and having a higher food intake. 3. The second hypothesis was partially supported. In the interference experiments between larvae of the same instar or different instars, mean handling time did not change significantly with increasing predator density, and attack rate did not change for second and third instars but decreased curvilinearly for fourth and fifth instars. Interference between some instars could not be studied because insufficient second instars were available at the same time as fourth and fifth instars, and most third instars were eaten by fourth and fifth instars in the experiments. Prey capture always decreased with decreasing attack rate. Therefore, interference reduced prey consumption in fourth and fifth instars, but not in second and third instars. The varying feeding responses of different instars should be taken into account when assessing their role in predator–prey relationships in the field.     

Aspects descriptifs du comportement alimentaire chez la larve de Plectrocnemia conspersa (Trichoptera,Polycentropodidae)

Die netzspinnenden Polycentropodidae-Trichopterenlarven sind als fleisch-fressend bekannt. In dieser Arbeit wird das Beutefangverhalten der Larve von P. conspersa beschrieben. Es besteht aus sieben nacheinanderfolgenden Vorgängen, die durch stereotype Einstellungen und Bewegungen gekennzeichnet sind. Der Effekt der Reiz-Intensität auf diese Verhaltensweisen wurde untersucht (Abb. 9). Das Beutefangverhalten gesättigter Larven läßt vermuten, daß zwei verschiedene Mechanismen es beherrschen.     

Ultrasound production during stridulation by hydropsychid larvae (Trichoptera)

The stridulatory apparatus of eight species of 5th instar caddis larvae of the family Hydropsychidae were compared using the scanning electron microscope. This revealed the presence of secondary structures associated with each main ridge of the file in some species. Slight differences occur in the number of ridges which form the plectra. The sounds produced by two coexisting species of hydropsychid larvae were recorded and temporal and frequency analysis carried out. These sounds are found to extend far into the ultrasonic range and appear to show only minor interspecific differences. The occurrence of stridulatory behaviour during territorial defence and its significance in relation to the ecology of the larvae is discussed. Some physical parameters affecting sound reception in the near- and far-field are presented and this leads to speculation on the existence of a possible hearing mechanism.     

Phylogeny of the Polycentropodidae (Insecta: Trichoptera) based on protein-coding genes reveal non-monophyletic genera

We tested the previous hypotheses of the phylogenetic position and monophyly of the caddisfly family Polycentropodidae. We also tested previous hypotheses about the internal generic relationship within the family by including 15 ingroup genera, many of them also represented by the genotype. All families that were previously taxonomically associated with the polycentropodids were included in the analysis. The total data set of 2225bp representing sequences of combined nuclear and mitochondrial genes and 171 taxa, was analyzed using Bayesian inference. We found strong support for a monophyletic Polycentropodidae with Ecnomidae as the closest sister group. The recently erected families Kambaitipsychidae and Pseudoneureclipsidae were monophyletic and distantly related to the Polycentropodidae. Within Polycentropodidae, monophyly and validity of the genera Neucentropus, Neureclipsis, Cyrnus, Holocentropus, Tasmanoplegas, Pahamunaya, Cernotina and Cyrnellus was strongly supported, while the genera Polycentropus, Polyplectropus, Plectrocnemia, Placocentropus and Nyctiophylax were all polyphyletic. The New Caledonian species were polyphyletic and represented three distinct clades. The sister group to the New Caledonian clades are from Australia, New Zealand and Chile, respectively. The Vanuatu species evolved after dispersal from the Fiji Islands. New internal primers for cytochrome oxidase I sequences of Trichoptera are introduced.     

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.     

Two New Species of the Genus Plectrocnemia Stephens (Trichoptera: Polycentropodidae) from the Russian Far East

Two new species of the genus Plectrocnemia Stephens, Plectrocnemia levanidovae, sp. n., from Sakhalin Island and the southern Kuril Islands, and Plectrocnemia martynovae, sp. n., from southern Primorye, are described and illustrated. The new species belong to the P. tortosa Group and are the sister species of P. tortosa Banks, from China, and P. appensata Mey, from Vietnam.     

Optimal foraging by the swallow (Hirundo rustica, L): Prey size selection

The foraging ecology of the swallow (Hirundo rustica) was investigated in the field and compared with predictions of optimal foraging theory. Prey items were selected primarily by size. The inclusion of an item in the diet depended on the absolute abundance of the high-ranking prey and not of the low-ranking ones. Small items of low profitability were, however, included when food was abundant and more small items were taken when they were relatively abundant. Energetics data are used to show that it is profitable in terms of net energy gain for the swallow to take a mixture of large and small items, whereas optimal foraging theory would predict exclusive specialization on large, high-ranking items. Other possible explanations for the inclusion of small items in the diet are discussed.