Habitat characterization of the morphologically similar mayfly larvae,Caenis and Tricorythodes (Ephemeroptera)

The larvae of Caenis (Caenidae) and Tricorythodes (Tricorythidae), once considered to be confamilial, have notable morphological and behavioural similarities. Univariate and multivariate (discriminant analysis) techniques were used to determine which environmental variables best characterized the larval habitats of Caenis and Tricorythodes at 40 sample sites on 29 rivers within the Interior Plains of Alberta, Canada. River width, depth and substrate type distinguished riverine habitats of the two genera. Larvae of Tricorythodes occurred in wide rivers of varying depths that possessed coarse substrates. Although larvae of Caenis occurred in a variety of habitats, they were found more frequently on stable substrates in narrow, deep rivers.     

Increments to genus Chamaecrista (Caesalpiniaceae: Cassiinae) from Bolivia and from Atlantic and Planaltine Brazil

Six taxa of genusChamaecrista are described: In sect.Apoucouita (Bentham) Irwin & Barneby,Ch. amorimii Barneby andCh. pteropoda Barneby, both from Atlantic Bahia; in sect.Absus ser.Incurvatae Irwin & Barneby,Ch. caspariifolia Barneby andCh. linearifolia var.latifolia Barneby, both from interior Minas Gerais; in sect.Absus ser.Hedysaroides Irwin & Barneby,Ch. fulgida Barneby, from northern Goiás; and in ser.Prostratae (Bentham) Irwin & Barneby,Ch. chiquitana Barneby, from lowland Bolivia. The affinities and differential characters of each are pointed out, and all but var.latifolia are illustrated.     

The early life history of kurosoi,Sebastes schlegeli (Scorpaenidae), in the Sea of Japan

Larval and juvenile stages of kurosoi,Sebastes schlegeli, are described and illustrated from wild specimens. Some ecological aspects of larvae and juveniles are also described. Notochord flexion occurred between 5.6–7.5 mm SL. Transformation occurred between 13–20 mm SL. Preflexion and flexion larvae ofS. schlegeli can be distinguished from similar larvae by the pigmentation of the dorsal and ventral midlines of the tail and absence of pigmentation on the ventral portion of the rectum. After notochord flexion, the dorsal and lateral regions in both larvae and pelagic juveniles were heavily pigmented, suggesting adaptation for neustonic life style. Larvae and juveniles were caught at many coastal stations, but did not occur in cooler offshore waters. Larvae smaller than 20 mm SL inhabited surface waters. Until ca. 40 mm SL, juveniles inhabited mainly surface waters (without drifting seaweed), but also used other habitats, such as the drifting seaweed, and near the sea bed. Small larvae (<7 mm SL) fed mainly on copepod nauplii. Larger larvae fed on calanoid copepodites andEvadne nordmanni. Pelagic juveniles fed mainly on fish eggs, with fish larvae also being important food items for some individuals. Most food items taken by juveniles that were associated with drifting seaweed were eggs with attaching filaments (Cololabis saira andHyporhamphus sajori), suggesting that the high density of such food items both attracts and keeps juveniles around drifting seaweed.     

Isolation of spore-forming bacilli from mosquitoes in natural breeding habitats in Iraq

New isolates of spore-forming bacilli from larvae and pupae of 3 species of mosquitoes are recorded in central Iraq.Bacillus sphaericus Meyer and Neide was isolated fromCulex pipiens (L.) larva.Bacillus carotarum Koch andBacillus cereus Frankland & Frankland were isolated fromTheobaldia longiareolata (Macquart) pupae.Bacillus laterosporus Laubach andBacillus thuringiensis (H 18) were isolated fromAedes caspius (Pallas) larvae. In addition, unidentifiedBacillus spp. were isolated fromCx. pipiens, T. longiareolata andAe. caspius larvae. Examination of soil samples collected from mosquito natural breeding habitats revealed isolates ofB. cereus, Bacillus thuringiensis H4a 4b; H 12 and H 16 and an unidentifiedBacillus sp.

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Résumé Des souches bactériennes sporogènes sont isolées de moustiques qui se trouvent dans la région centrale de l'Irak. Les résultats obtenus sont les suivants:Bacillus sphaericus Meyer & Neide [Culex pipiens (L.), larve],Bacillus carotarum Koch etBacillus cereus Frankland & Frankland [Theobaldia longiareolata (Macquart), nymphe],Bacillus laterosporus Laubach etBacillus thuringiensis (H 18) [Aedes caspius (Pallas), larvel]. L'examen des larves deCulex pipiens. T. longiareolata etAe. caspius, ainsi que l'analyse des échantillons du sol prélevés dans la région montrent la présence deBacillus cereus, Bacillus thuringiensis H4a 4b; H12 plus H16 et d'autresBacillus non identifiés.

     

Diversity and structure of ant communities associated with oak,pine, eucalyptus and arable habitats in Portugal

Summary In central Portugal, 28 species of ants were found in oak, 25 in pine, 35 in eucalyptus and 12 in arable habitats, a total of 43 species. They include five numerically dominant species, the exotic Argentine ant.Linepithema (Iridomyrmex) humile and four native species,Crematogaster scutellaris, Pheidole pallidula, Tapinoma nigerrimum andTetramorium hispanicum. L. humile occurred in 34% of sampled sites. When present, it was abundant in all three arboreal habitats, where it was associated with strikingly decreased ant species richness and equitability. Such diversity was greater inL. humile-colonised arable habitats, where the ant was much less abundant than in the arboreal habitats.WhereL. humile was absent,C. scutellaris andP. pallidula were usually co-dominants in oak and pine, andT. nigerrimum andT. hispanicum in the arable habitat, but all were absent or rare in eucalyptus. Ants were numerically least abundant in eucalyptus but, in the absence ofL. humile, species richness was greater and the community more equitable than in the other habitats.L. humile-absent arable habitats supported the poorest and least equitable ant community.     

Response of Three Hymenopteran Parasitoids Introduced for Fruit Fly Control to a Gall-Forming Tephritid,Procecidochares alani(Diptera: Tephritidae)

The response of three larval–pupal parasitoids,Diachasmimorpha longicaudata(Ashmead),Diachasmimorpha tryoni(Cameron), andTetrastichus giffardianusSilvestri, to the Hamakua pamakani gall fly,Procecidochares alaniL., was determined in the laboratory. We also observed responses of these parasitoids to their normal rearing hosts,Bactrocera dorsalis(Hendel) andCeratitis capitata(Weidemann).D. tryonilanded on pamakani galls or on dishes containingP. alanilarvae as frequently as on dishes containingC. capitata.In contrast,D. longicaudataonly rarely landed on the galls.D. tryoniandD. longicaudataoviposited in galls in fewer than 1% of our observations.D. longicaudataprobedP. alanilarvae as frequently asB. dorsalislarvae, but no parasitoid offspring were observed.D. tryonioviposited more frequently inC. capitatathanP. alani.NoD. tryonideveloped inP. alanilarvae.T. giffardianuslanded on pamakani galls andP. alanilarvae more frequently than any other host substrate. In contrast,T. giffardianusentered galls with artificially opened windows one time in 10 observations. We observed 12% parasitism ofP. alanilarvae dissected from the galls and 20% of parasitismP. alaniin the windowed galls. We discuss the implications of our results for future augmentative or classical biological control studies.     

Effects of long-term grazing on the morphological and functional traits of Leymus chinensis in the semiarid grassland of Inner Mongolia, China

Livestock grazing represents a major human disturbance to grasslands throughout the world. We evaluated the effects of long-term grazing (>20 years) on a dominant perennial grass species, Leymus chinensis (Trin.) Tzvel., in the semiarid grassland of Inner Mongolia, China, in terms of its morphological and functional responses. L. chinensis, one of the most abundant species in semiarid grassland, had significantly smaller leaf area, fewer vegetative tillers and shorter shoot internodes length, but significantly greater specific leaf area for the individuals in the grazing plot than those in the exclosure (grazing-free) plot. Long-term grazing also altered the relative distribution of biomass to leaves, roots and rhizomes. The biomass, coverage and the number of species were lower in the grazing plot by 50–70% in comparison with those in the grazing-free plot. In addition, the long-term grazing substantively decreased the physiological capacities of this grass species, including significantly lower net photosynthetic rate, apparent quantum efficiency, photochemical efficiency of PSII and water use efficiency. Significantly higher stable oxygen isotope ratios (δ ¹⁸O) of the soil water in the grazing plot than those in the grazing-free plot indicated a much higher soil evaporation in the grazing plot because of less litter coverage. Seasonal patterns in the δ ¹⁸O values of the stem water of L. chinensis and three other common species in the grazing and grazing-free plots indicated that plants in the grazing and grazing-free plots might shift their water sources differently from a dry month (June) to a wet month (August). This study illustrated the importance of using different approaches to study the possible responses of grass species in arid regions to human disturbances, such as long-term grazing.     

The predator-prey relationship of perch,Perca fluviatilis,larvae and zooplankton in two Scottish lochs

Synopsis Food consumption of perch larvae and the impact of this on zooplankton were examined in two adjacent shallow Scottish lochs. Maximum annual abundance of zooplankton occurred in mid-May at L. Kinord with minimum values in mid-June. Copepods were prominent in spring but were followed by a multi-species community of cladocerans and rotifers in summer. At L. Davan zooplankton biomass remained high through summer with cladocerans dominating andDaphnia longispina the most frequent species. Availability of food items was a principal factor governing feeding behaviour of larvae. Copepodite stages were initially the most common item in the diet in L. Kinord in 1976 and 1977 and rotifers the principal food in June 1977, reflecting the dominance of these items in the zooplankton. Cladocerans were dominant in the plankton community in L. Davan and constituted the greater part of food intake. Overlying this general pattern there was an increase in the size of food items taken by larvae with time and also a definite pattern of food selection for copepods, with initially selection for smaller copepodite stages and later for larger stages and adults. On most occasions larvae selected forCyclops strenuus abyssorum andPolphemus pediculus and selected againstDaphnia longispina. The reduction in the total zooplankton biomass attributed to perch larvae was minimal, with the exception of mid-June at L. Kinord in 1976. However, predation on particular species and copepodite stages was occasionally intense and may have impacted the zooplankton populations.     

Factors affecting entomopathogenic nematode infection ofPlutella xylostella on a leaf surface

We investigated the ability of entomopathogenic nematodes to infect diamondback moth (DBM),Plutella xylostella (L.) (Lepidoptera: Plutellidae) on a leaf surface. In a leaf disk assay, mortality of late stage DBM larvae ranged from <7% caused bySteinernema kushidai Mamiya to >95% caused byS. carpocapsae (Weiser) All strain. LC₅₀ values forS. carpocapsae, S. riobravis Cabanillas, Poinar & Raulston, andHeterorhabditis bacteriophora Poinar NC1 strain were 14.6, 15.4, and 65.4 nematodes/larva, respectively.S. carpocapsae, S. riobravis, andH. bacteriophora caused 29%, 33%, and 14% mortality of DBM pupae, respectively. DBM mortality caused byS. carpocapsae on radish declined at low (<76%) to moderate (76–90%) RH, because nematode survival and infectivity declined at low (<76%) to moderate (76–90%) RH. However, DBM mortality caused byS. riobravis did not decline with RH.S. riobravis survival declined with RH, but infectivity did not. Overall, nematode survival and infectivity to DBM larvae were lower forS. riobravis than forS. carpocapsae. In addition, DBM mortality was higher on radish plants (pubescent leaves) than on cabbage plants (glaborous leaves).     

Crossing experiments of lettuce cultivars and species (Lactuca sect.Lactuca,Compositae)

The degree of relationships withinLactuca sativa and three wild relativesL. serriola, L. saligna, andL. virosa was studied by observing the performance, vigour and fertility of the F 1 hybrids obtained from crosses made in and between the four species. The crosses ofL. saligna ×L. virosa and the reciprocal crosses produced no hybrids.L. saligna andL. virosa are the least related of the four species.L. sativa ×L. serriola and the reciprocal crosses were successful and produced fertile hybrids These two species are genetically very closely related.L. saligna is known to produce, as a female parent, hybrids withL. sativa andL. serriola. Now the reciprocal cross was successful for the first time, so the unability to obtain hybrids in the past was based on the choice of accessions and not caused by unilateral incompatibility.L. virosa ×L. sativa and the reciprocal combination produced hybrids. The combinationL. serriola ×L. virosa produced hybrids with very limited fertility. In contrast to earlier reports (sterile hybrids) one combination of the reciprocal cross too produced hybrids with very limited fertility.—Some of theL. saligna ×L. sativa (and reciprocal) hybrids were found to look strikingly likeL. serriola. This adds evidence for the descent ofL. serriola andL. sativa:L. saligna also made part of the ancestral complex of the cultivated lettuce.     

Experimental formulations ofBacillus sphaericus for the control of anopheline and culicine larvae

Summary Four experimental formulations ofBacillus sphaericus Neide (2362 isolate) were evaluated for larvicidal activity against culicine and anopheline larvae in several natural and artificial habitats. A granular formulation (5% primary powder) was tested against natural populations of mosquitoes in two simulated habitats in Florida and in maturing and reflooded rice fields in Louisiana. Larvae ofCulex quinquefasciatus Say were reduced by 97 and 99% after application of the granules at the rate of 10 kg/ha to polluted tanks and 2.5 kg/ha to sod-lined potholes, respectively. Anopheline andPsorophora columbiae (Dyar and Knab) larvae were reduced by 68 and 92–100%, respectively, after application of 5 kg granules/ha to rice fields. A flowable concentrate (12.8% primary powder) applied to unpolluted and organically enriched habitats in Florida at 0.25 kg/ha reduced populations ofCulex spp. by 93–100% and 99%, respectively. Sustained-release briquets (5% primary powder) applied at the rate of one half briquet/1.8 m² sod-lined potholes reduced larval populations ofCx. quinquefasciatus by 88–95% for up to 2 weeks in open sunlight. Sustained-release pellets (30% primary powder) applied to small woodland pools in Memphis, TN at the rate of four pellets/pool virtually eliminated larval populations ofCx. restuans Theobald for over 8 days. Variable persistance of larvicidal activity was noted for the other treatments depending on the formulation, target species and habitat.     

Processing of leaf matter by lake-dwelling shredders at low oxygen concentrations

Organic sediments in freshwaters are regularly subject to low concentrations of oxygen. The ability of detritivores to sustain their feeding in such conditions should therefore be of importance for the decomposition process. In the present study, aquaria were used to determine processing rates of five lake-dwelling shredders at three different oxygen concentrations; normoxic (9 mg O₂ l^–1) and two levels of hypoxia (1 and 2 mg O₂ l^–1). Discs of alder leaves (Alnus glutinosa (L.)) were used as food. Four species of caddisfly larvae (Trichoptera Limnephilidae) and the isopod, Asellus aquaticus (L.) were compared in the experiments. Significant differences in processing rates per g animal biomass were found both at normoxia and 2 mg oxygen l^–1. At l mg O₂ l^–1 none of the invertebrates fed on leaf discs. The caddisfly larvae Halesus radiatus (Curtis), being one of the two most efficient shredders at normoxia, did not feed at 2 mg oxygen l^–1. The other species fed at rates 15–50 of that at normoxia. The least efficient shredder at normoxia, A. aquaticus was similar to two of the trichopterans at 2 mg O₂ l^–1. This study shows that the importance of specific shredder species may shift in case of hypoxia. Species-specific traits regarding oxygen sensitivity may also be influential for distribution patterns of shredder species both within and between lakes.     

Function of Ventral and Lateral Processes in Larvae of Chironomus (Diptera, Chironomidae)

Oxygen consumption by larvae of five Chironomus species from the Plumosus group belonging to different larval forms was studied. Larvae of C. agilis ( f. l. reductus) were unable to utilize oxygen at its concentrations lower than 1 mg/l. Larvae of C. plumosus ( f. l. plumosus) used oxygen from water at concentrations higher than 0.7 mg/l; pupas of this species and larvae of C. borokensis ( f. l. plumosus) utilized oxygen at concentrations lower than 0.4 mg/l. C. entis and C. muratensis (both-- f. l. semireductus) utilized oxygen from water at its concentrations up to 0.05 mg/l. The lack of correlation between the rate and ability of larvae to use oxygen at low concentrations and the degree of development of processes allows suggesting that these structures are not additional respiratory organs, as is commonly accepted. At the same time, ability of species to inhabit under conditions of oxygen deficiency correlates directly with the size of the processes. Therefore, ventral and lateral processes are suggested to perform a function of excretion of anaerobic metabolism metabolites.     

Grazing dynamics on a Caribbean reef-building coral

Corals in certain Caribbean coral reef habitats are constantly grazed-on due to the territorial marking behavior of the stoplight parrotfish Sparisoma viride. We studied the grazing dynamics on the Caribbean reef-building coral Montastraea annularis. We transplanted colonies to algae-dominated reefs (Rosario Islands, Cartagena, Colombia), where they encountered higher grazing pressure. We counted grazed polyps every month throughout a year. Over the course of a year, 4,101 different grazed polyps were counted on lobe-like M. annularis transplants ( n =23). Grazing was evaluated on a monthly basis as the probabilities of all the possible transitions among four grazing categories (0%, >0–1%, >1–5%, >5% grazed tissue), uncovering a dynamic process. Higher transition probabilities were always between 0 and 1% (coral tissue grazed) grazing states, indicating that grazing did not usually exceed 1% per coral per month. The probability of remaining uninjured in a month was 0.19, 0.17 of a change from 0–1% grazing state, 0.31 of remaining at 1%, and of full recovery from 1% grazing was 0.16. More than one month was usually required for complete recovery ( P<<1) probably due to both steady grazing pressure and slow regeneration rates. Since the marking behavior of the parrotfish was not as common on other zones of the reef no comparison on the grazing among environments was possible. In spite of this, it is possible to have stable transplanted populations of corals such as M. annularis on algae-dominated Caribbean reef environments due to their tolerance to the natural grazing pressure.Communicated by: K. S. Sealey     

Records on parasitoids of smaller poplar borer,Saperda populnea [Coleoptera,Cerambycidae] along the Danube in Bulgaria

During the period 1986–1988 the parasitoids of smaller poplar borer,Saperda populnea L. (Coleoptera, Cerambycidae) along the Danube in Bulgaria were studied. A total of 898 smaller poplar borer galls were investigated—289 in 1986, 404 in 1987, and 205 in 1988. In the particular years the parasitoids of smaller poplar borer namelyBillaea irrorata Meig.(Diptera, Tachinidae), Dolichomitus populneus Ratz. (Hym.: Ichneumonidae), andIphiaulax impostor Scop. (Hym.: Braconidae) destroyed from 13.1 up to 28.0% of the pest larvae, thus decreasing their frequency together with the other limiting factors by 56.1% up to 81.2%. The tachinid flyB. irrorata decreased the smaller poplar borer larvae frequency by 9.3% up to 18.9%, while the ichneumonoidD. populneus, and the braconoidI. impostor destroyed insignificant percentages of these larvae—0.5% up to 1.7% and 0.5% up to 2.5% resp. The flight period of the pest preceded or almost coincided with the ones ofD. populneus, andI. impostor. The flyB. irrorata always appeared last and its flight period was expanded.      

Diet,food preference,and algal availability for fishes and crabs on intertidal reef communities in southern California

Synopsis Herbivory by wide-ranging fishes is common over tropical reefs, but rare in temperate latitudes where the effects of herbivorous fishes are thought to be minimal. Along the west coast of North America, herbivory by fishes on nearshore reefs is largely restricted to a few members of the Kyphosidae, distributed south of Pt. Conception. This paper presents information on natural diets and results from feeding choice experiments for two abundant kyphosids from intertidal habitats in San Diego, California —Girella nigricans andHermosilla azurea, and similar data for the lined shore crab,Pachygrapsus crassipes, which also forages over intertidal reefs. These results are compared with the availability of algae in intertidal habitats measured during summer and winter, on both disturbed and undisturbed habitats. The diets of juveniles ofG. nigricans andH. azurea collected from nearshore habitats were dominated by animal prey (mainly amphipods), but adults of these fishes, andP. crassipes, consumed algae nearly exclusively, with 26, 10, and 14 taxa of algae identified fromG. nigricans, H. azurea, andP. crassipes, respectively. Algae with sheet-like morphologies (e.g.Ulva sp.,Enteromorpha sp., members of the Delesseriaceae) were the principal algae in the diets of the fishes, and calcareous algae (e.g.Corallina sp.,Lithothrix aspergillum) and sheet-like algae (Enteromorpha sp.) comprised the greatest identifiable portion of the shore crab's diet. Feeding choice experiments indicated that the fishes preferred filamentous algae (e.g.Centroceras clavulatum, Polysiphonia sp.,Chondria californica) and sheet-like algae (e.g.Enteromorpha sp.,Ulva sp.,Cryptopleura crispa) over other algal morphologies, whereas the shore crab chose jointed calcareous algae (e.g.Lithothrix aspergillum, Corallina vancouveriensis, Jania sp.) most frequently. The diets and preferences for algae by the fishes were generally most similar to the assemblage of algae available in early successional (disturbed) habitats during summer when sheet-like and filamentous algae are abundant. The shore crab exhibited the opposite trend with a diet more similar to late successional (undisturbed) habitats.     

Effects of grazing intensity on growth,reproduction, and abundance of three palatable forbs in Kansas tallgrass prairie

The effects of different intensities of cattle grazing on theaboveground growth, reproduction, and abundances of three palatable forbs werestudied in native tallgrass prairie. Populations of Asterericoides, Ruellia humilis, andAmorpha canescens were sampled at peak flowering duringthe1993–1995 growing seasons in four annually-burned sites varying incattle stocking density [ungrazed, low, moderate, high]. The threeforbs exhibited reduced shoot growth and/or reproduction under moderate toheavy grazing, and in no case did grazing increase any measure of plantperformance. Ruellia showed reduced shoot height andbiomass, percentage of stems flowering, and reproductive biomass in response tograzing. Aster showed decreases in shoot biomass andheightwith grazing. Amorpha showed no change in shoot orreproductive biomass, but a decrease in percent of flowering stems and inreproductive allocation with grazing. Patterns in the percentage of stemsgrazedindicated generally high but variable palatability among these species. Bycontrast, the three species showed inconsistent population response to grazing.Abundance (frequency) of all three species indicated no short-term changebetween years in response to grazing intensity. Responses of these speciesdiffer considerably from those of most other perennial tallgrass prairie forbsthat are unpalatable, unconsumed, and increase in performance (e.g. size,abundance) due to release from competition from the dominant grasses underungulate grazing. The results demonstrate that immediate aboveground growth andreproductive responses of established adults to grazing are not good predictorsof grazer effects on population abundances in tallgrass prairie.     

Phylogeny and habitat adaptations within a monophyletic group of wetland moss genera (Amblystegiaceae)

Genus level phylogenetic patterns within a monophyletic group of wetland mosses consisting ofTomentypnum, Hamatocaulis, Scorpidium, Conardia, Calliergon, Warnstorfia, Straminergon, andLoeskypnum (Amblystegiaceae) are cladistically analysed, usingPalustriella and partlyCratoneuron as outgroups. The ingroup consists of two clades, one withTomentypnum, Hamatocaulis andScorpidium, the other with the other ingroup genera. The second clade gets completely resolved only with the inclusion of habitat data. The adaptation to relatively dry wetland habitats probably evolved in the ancestor ofStraminergon andLoeskypnum, the species ofCalliergon andWarnstorfia, which are more ancestral, growing in wetter habitats. The more primitive taxa of the ingroup, as well asPalustriella species, occur in relatively mineral-rich habitats and adaptations to poorer habitats occurred several times in the two clades.     

Silurian Leptaeninae (Brachiopoda) from Gotland, Sweden

Strophomenid brachiopods belonging to the generaLeptaena andLepidoleptaena are described from the uppermost Llandovery — Ludlow succession of Gotland, Sweden. In Gotland,Lepidoleptaena comprises the single speciesL. poulseni, andLeptaena includes four species:L. rhomboidalis, L. sperion, L. depressa andL. parvirugata n. sp.L. depressa shows a considerable amount of morphological variation, which is recognised in the two new subspeciesLeptaena depressa visbyensis n. ssp. from the Llandoverian — Wenlockian Visby Formation, andL. depressa lata n. ssp. from the mid-Wenlockian Slite Group. The distribution of the different species is largely substrate-dependent, withLeptaena rhomboidalis andLepidoleptaena poulseni adapted to high-energy environments with firm substrates, whereas the remaining species preferred fine-grained substrates in low-energy environments.      

Effects of structural habitat on drift distance and benthic settlement of the caddisfly,Ceratopsyche sparna

We conducted two experiments in flow-through, artificial streams to examine how habitat structure affected drift and benthic resettlement of larval hydropsychid caddisflies (Ceratopsyche sparna). In the first experiment, we quantified drift distance and the number of times larvae re-entered the drift in 9.0 × 0.51-m channels with contiguous patches (ea. 2.5-m long) of biofilm-covered gravel, biofilm-covered cobbles (– Cladophora), and Cladophora-covered cobbles (+ Cladophora). In the second experiment, we tracked nocturnal movements of larvae after benthic settlement in 2.8 × 0.1-m channels, each containing one of the three habitat types. In experiment 1, drift distance was (1) greatest in gravel and lowest in cobbles + Cladophora, (2) inversely related to hydraulic roughness of habitats, (3) independent of body size, and (4) similar for live and dead larvae. Average drift distance was relatively short (<2.5 m), regardless of habitat type. Number of drift re-entries also varied among habitats, being greatest in gravel and lowest in cobbles + Cladophora. No larvae re-entered the drift after settling in Cladophora patches. Results from experiment 2 revealed that drift propensities were higher for larvae in biofilm-covered gravel and cobbles than in cobbles + Cladophora. Larvae remaining in substrate patches (i.e. not drifting) laid fewer draglines in biofilm-covered stones than in Cladophora patches. Extent of benthic movement (i.e., crawling) by non-drifting larvae did not differ significantly among habitats. However, distance moved did differ with flow direction, being 4× greater downstream than upstream. These results highlight how local substrate and hydraulic conditions interact to affect small-scale movements of caddisfly larvae.