Decomposition of Eucalyptus globulus leaves and three native leaf species (Alnus glutinosa, Castanea sativa and Quercus faginea) in a Portuguese low order stream

Leaf decomposition of the exotic evergreen Eucalyptus globulus (eucalyptus), and three native deciduous tree species, Alnus glutinosa (alder), Castanea sativa (chestnut) and Quercus faginea (oak), was compared in a second order stream in Central Portugal. Changes in dry weight, nitrogen and polyphenolic compounds and microbial colonization were periodically assessed for three months.Negative exponential curves fit the leaf weight loss with time for all leaf species. Mass loss rate was in the order alder (K = 0.0161) > chestnut (K = 0.0079) > eucalyptus (K = 0.0068) > oak (K = 0.0037). Microbial colonization followed the same pattern as breakdown rates. Evidence of fungal colonization was observed in alder after 3 days in the stream, whereas it took 21 days in oak leaves to have fungal colonization. Fungal diversity was leaf species-dependent and increased with time. In all cases, percent nitrogen per unit leaf weight increased, at least, at the initial stages of decay while soluble polyphenolics (expressed as percentage per unit leaf weight) decreased rapidly in the first month of leaves immersion.Intrinsic factors such as nitrogen and polyphenolic content may explain differences in leaf decomposition. The possible incorporation of eucalyptus litter into secondary production in a reasonable time span is suggested, although community balance and structure might be affected by differences in allochthonous patterns determined by eucalyptus monocultures.     

Leaf Barriers to Fungal Colonization and Shredders (Tipula lateralis) Consumption of Decomposing Eucalyptus globulus

Abstract Herein we assess the importance of leaf cuticle, polyphenolic, and essential oils contents of Eucalyptus globulus leaves to hyphomycete colonization and shredder consumption. Optical and electron microscopy revealed that, at least during the first 5 weeks of conditioning, the cuticle remains virtually intact. Stomata provide the main access for hyphae to internal leaf tissues and, eventually, for spore release. We suggest that in E. globulus leaves, fungal decomposition progresses predominantly in and from the eucalyptus leaf mesophyll to the outside. Malt extract agar media supplemented with either eucalyptus essential oils or tannic acid completely inhibited (Articulospora tetracladia, Lemonniera aquatica, and Tricladium gracile) or depressed (Heliscus lugdunensis, Lunulospora curvula, and Tricladium angulatum) aquatic hyphomycetes growth. The transference of both secondary compounds to alder leaves induced similar and significant reduction in Tipula lateralis larval consumption. Results consistently indicate that eucalyptus oils are stronger deterrents than polyphenols. The waxy cuticle of E. globulus appears to be a key physical factor delaying fungal colonization during decomposition. We hypothesize that the relative influence of leaf phenols and essential oils to aquatic hyphomycetes and shredders may be related to three main factors: (a) initial distribution of such compounds in the leaves; (b) possibility of their decrease through decomposition; and (c) consumption strategies of detritivores. Received: 8 July 1998; Accepted: 21 December 1998     

Toxicity of acephate to larvae of gypsy moth as a function of host plant and bioassay method

We examined toxicity of acephate to third-instar gypsy moth, Lymantria dispar (L.) (Lepidoptera: Lymantriidae), under different conditions of administration method, availability of food to larvae during bioassay, host plant, and activity of detoxifying enzymes. Larvae that had been fed field-collected foliage of white alder (Alnus rhombifolia Nutt.) were less susceptible 48 h after treatment with topically applied acephate if they were allowed to continue feeding on foliage during the bioassay period (LD₅₀= 60.6 μg/g larva ) than if they were not (LD₅₀= 13.5 μg/g larva ). All surviving larvae were replaced on their original food plant after the 48-h bioassay; of these, 14.4% of the larvae not fed during treatment died before pupation, compared with 1.3% of the larvae fed alder during treatment. The LD₅₀ obtained for topically treated larvae reared and treated on Douglas-fir, Pseudotsuga menziesii (Mirb.) Franco, (51.1 μg/g larva) was comparable to that obtained for larvae fed alder (60.0 μg/g larva) throughout treatment. Larvae treated orally with acephate, however, were slightly more susceptible when reared on Douglas-fir (LC₅₀, 20.3 ppm ) than when reared on alder (LC₅₀, 27.0 ppm ). Post-treatment mortality in orally treated larvae was 10.3% in those fed alder and 9.5% in those fed Douglas-fir. Higher cytochrome P-450 activities in larvae reared on Douglas-fir apparently did not enhance tolerance to acephate. Both sexes of orally treated larvae took significantly longer to pupate than did controls on both foliage types, as did topically treated males fed Douglas-fir. Pupal weight generally was slightly, but not always significantly, higher in treated than untreated larvae under all dietary and treatment regimes.     

Breakdown of wood in the Agüera stream

SUMMARY 1. Breakdown of wood was compared at three sites of the Agüera catchment (Iberian Peninsula): two oligotrophic first‐order reaches (one under deciduous forest, the other under Eucalyptus globulus plantations) and one third‐order reach under mixed forest, where concentration of dissolved nutrients was higher. 2. Branches (diameter = 3 cm, length = 10 cm) of oak (Quercus robur), alder (Alnus glutinosa), pine (Pinus radiata) and eucalyptus, plus prisms (2.5 × 2.5 × 10 cm) of alder heartwood were enclosed in mesh bags (1 cm mesh size) and placed in the streams. Mass loss was determined over 4.5 years, whereas nutrient, lignin and ergosterol were determined over 3 years. In order to describe fungal dynamics, ergosterol was also determined separately on the outer and inner parts of some branches. 3. Breakdown rates ranged from 0.0159 to 0.2706 year^?1 with the third‐order reach having the highest values whatever the species considered. The most rapid breakdown occurred in alder heartwood and the slowest in pine branches; breakdown rates of oak, eucalyptus and alder branches did not differ significantly. 4. The highest nitrogen and phosphorus contents were found in alder, followed by oak, while pine and eucalyptus had low values. During breakdown, all materials rapidly lost phosphorus, but nitrogen content remained constant or slightly increased. Lignin content remained similar. 5. Peaks of ergosterol ranged from 0.023 to 0.139 mg g^?1 and were higher in alder than in other species in two of the three sites. The third‐order reach generally had the greatest increase in ergosterol, especially in alder branches, eucalyptus and alder heartwood. The overall species/site pattern of fungal biomass was thus consistent with the observed differences in breakdown. 6. When compared with leaves of the same species decomposing at these sites, wood breakdown appeared to be less sensitive to the tree species but more sensitive to stream water chemistry. Although wood breakdown is slower and its inputs are lower than those of leaf litter, its higher resistance to downstream transport results in a relatively high standing stock and a significant contribution to the energy flux.     

Effect of leaf litter characteristics on leaf conditioning and on consumption by Gammarus pulex

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Species diversity of freshwater hyphomycetes in some streams of Pakistan. III. Autumnal colonization of freshwater hyphomycetes on bait leaves

Significantly more species of freshwater hyphomycetes colonized bait leaves of alder (16 species) and willow (14 species) during early submersion period (1 wk) than those of oak (8 species). Production of conidia was also higher on alder and willow leaves than on oak leaves. Higher amounts of dry mass were lost from the alder (28.6%) and willow leaves (29.4%) than from the oak leaves (18.7%). Rapid loss of dry mass was accompanied by rapid development of a fungal community. Fungal species took a longer time (6 wk) to reach their peak of occurrence on oak than on willow and alder leaves (3–4 wk).Flagellospora curvula dominated the assemblages of freshwater hyphomycetes on alder and willow leaves, andLunulospora curvula dominated the assemblage on oak leaves. The freshwater hyphomycete community showed higher values of species diversity (H value) on oak leaves than on alder and willow leaves.     

Green leaves enhance the growth and development of a stream macroinvertebrate shredder when senescent leaves are available

1. Freshly fallen green leaves and flowers of terrestrial plants enter temperate streams in spring and summer, when senescent leaf litter is often scarce. These resources appear to provide good supplementary food for macroinvertebrate shredders, but have some potential shortcomings as food or case material for caddisflies. 2. To compare suitability of green leaves or flowers and senescent leaves for the growth and development of stream shredders, we reared the caddisfly Lepidostoma complicatum in the laboratory with treatments that provided larvae with senescent (oak) and green (oak or maple) leaves separately, and also together, in case the combined use of both types of leaf may benefit the shredder. 3. Larvae supplied with green leaves alone grew at 65% of the rate of those provided with senescent leaves alone, due to their lower consumption rate. No individuals given green leaves alone developed into adults, whereas 70% of the individuals given senescent leaves alone did. Green leaves may inhibit larval consumption due to their high phenol content, or they may be unsuitable for case material because they are less tough than senescent leaves. 4. Larvae supplied with both senescent and green leaves (or flowers) had a higher growth rate and developed faster, than those given senescent leaves alone, whereas the proportions of successfully emerged individuals did not differ. Lepidostoma probably benefits from the higher nitrogen content of the green leaves when used together with senescent leaves. 5. These results suggest that green leaves (or flowers) cannot serve as an alternative food resource to senescent leaves, but that they can enhance the growth and development of a Lepidostoma stream shredder if senescent leaves are also available.     

Avidin expressed in transgenic tobacco leaves confers resistance to two noctuid pests,Helicoverpa armigera and Spodoptera litura

Fertile transgenic tobacco plants with leaves expressing avidin in the vacuole have been produced and shown to halt growth and cause mortality in larvae of two noctuid lepidopterans, Helicoverpa armigera and Spodoptera litura. Late first instar H. armigera larvae and neonate (<12-h-old) S. litura larvae placed on leaves excised from T₀ tobacco expressing avidin at 3.1–4.6M (moles/kg of fresh leaf tissue) had very poor growth over their first 8 days on the leaves, significant numbers had died by days 11 or 12 and all were dead by day 22 (H. armigera) or day 25 (S. litura). Similar results were obtained when late first instar H. armigera larvae were placed on leaves from T₁ plants expressing avidin at six different average concentrations, ranging from 3.7 to 17.3M. Two larvae on the lowest expressing leaves survived to pupation, but there was total mortality among the other groups and no relationship between avidin concentration and the effects on the larvae. Synergistic effects between avidin-expressing tobacco plants and a purified Bt toxin, Cry1Ba, were demonstrated. Late instar H. armigera larvae fed with leaves from T₂ plants expressing avidin at average concentrations of either <5.3 or >12.9M, and painted with Cry1Ba protein at a rate equivalent to an expression level of 0.5% of total leaf protein, died significantly faster than larvae given either of the two treatments alone. Larvae fed with avidin-expressing leaves painted with the protease inhibitor, aprotinin, at a rate equivalent to 1% of total leaf protein had mortality similar to those given avidin-leaves alone. There was no evidence of antagonism between these two proteins.     

Variation in growth of the detritivore-shredder Sericostoma personatum (Trichoptera)

1. We investigated the growth of the detritivore-shredder Sericostoma personatum by feeding groups of larvae on a fresh macrophyte, Potamogeton perfoliatus , conditioned sitka spruce needles, Picea sitchensis , conditioned alder leaves, Alnus glutinosa , conditioned ash leaves, Fraxinus excelsior , and a fresh filamentous green alga, Microspora sp. A sixth treatment group of larvae was fasted.
2. The nitrogen content of the food items ranged from 1.4% dry weight (DW) for Picea needles to 4.4% DW for Microspora filaments. Consumption of the various food items by Sericostoma differed significantly, being highest for Picea , and lowest for Potamogeton and Microspora .
3. The instantaneous growth rate ranged from −1.3% DW day⁻¹ in the fasting group to 0.75% DW day⁻¹ in the Alnus group. The growth rate of larvae fed on Alnus , Fraxinus and Microspora was similar, and significantly higher than that of the other three groups. An increase in the size of larval cases followed the same pattern as larval growth, although with less variation between food items.
4. Larvae fed on Microspora exhibited the greatest increase in fat content, while that of the larvae fed on Picea and those in the fasting group decreased. The gross growth efficiency (G/I%) of Sericostoma (larva + case) ranged from 2% when fed on Picea to 34% when fed on Microspora . Consumption was significantly correlated with the nutrient content of food items, whereas G/I% and growth rate were only weakly related to food quality.
5. The growth of Sericostoma varies with diet and the food items sustaining highest growth rate are not necessarily the 'typical' shredder food resources.     

Feeding of fall armyworm,Spodoptera frugiperda,on Bt transgenic cotton and its isoline

Studies on insect food intake and utilization are important for determining the degree of insect/plant association and host species’ resistance, and also for helping design pest management programs by providing estimates of potential economic losses, techniques for mass breeding of insects, and identifying physiological differences between species. We studied the feeding and development of fall armyworm, Spodoptera frugiperda (JE Smith) (Lepidoptera: Noctuidae), on transgenic (Bt) and non‐transgenic (non‐Bt) cotton. The larvae of S. frugiperda fed on Bt cotton had a longer development period (23.0 days) than those fed on non‐Bt cotton (20.2 days). Survivorship of S. frugiperda larvae fed on Bt cotton (74.1%) was lower than that of larvae fed on non‐Bt cotton (96.7%). Pupal weight of larvae fed on Bt cotton (0.042 g) was lower than that of larvae fed on non‐Bt cotton (0.061 g). The cotton cultivar significantly affected food intake, feces production, metabolization, and food assimilation by S. frugiperda larvae. However, it did not affect their weight gain. Intake of Bt‐cotton leaf (0.53 g dry weight) per S. frugiperda larva was lower than the intake of non‐Bt‐cotton leaf (0.61 g dry weight). Larvae fed on Bt‐cotton leaves produced less feces (0.25 g dry weight) than those fed on non‐Bt‐cotton leaves (0.37 g dry weight). Weight gain per S. frugiperda larva fed on Bt‐cotton leaves (0.058 g dry weight) was similar to the weight gain for larvae fed on non‐Bt‐cotton leaves (0.056 g dry weight). The cotton cultivar significantly affected the relative growth, consumption, and metabolic rates, as well as other nutritional indices: the figures were lower for larvae fed on Bt‐cotton leaves than for larvae fed on non‐transgenic cotton leaves.     

Defense characteristics of seral deciduous broad-leaved tree seedlings grown under differing levels of CO2 and nitrogen

Mixed broad-leaved forests are abundantly populated by several kinds of herbivore species in northern Japan. The life of herbivores depends strongly on the quality of food leaves. Leaf quality is changing with increasing atmospheric CO₂ and nitrogen deposition. Four seral species of deciduous broad-leaved tree seedlings (alder, birch, oak and maple) were raised in all four combinations of two levels of CO₂ and two levels of nutrient, to examine foliar defense traits. To evaluate the relative defense capacity of the four tree species, we used wild silkworms (Erisan; a generalist herbivore) as a bioassay material. Except with alder, the survival rate and longevity (ML₅₀) of the silkworms were least when they were fed with leaves of seedlings raised under high CO₂ and infertile soil conditions, and longest on a diet of leaves grown in ambient CO₂ and fertile soil, especially in birch and maple. The longevity of Erisan decreased in the order birch, oak, and maple. The longevity of Erisan fed with alder leaves was independent of CO₂ levels and was longer on alder seedlings grown in infertile soil conditions. Alder is an actinorhizal plant that can fix atmospheric nitrogen in root nodules formed by the actinomycetes Frankia sp. The activity of symbiotic microbes would have been enhanced by the greater amount of photosynthates received from the host plants at high CO₂, improving the food quality for the silkworms. It was concluded that in all but alder, leaf chemical traits, especially C/N ratio, affect the ML₅₀ of Erisan larvae.     

Survivorship and growth in the larvae of Luehdorfia japonica feeding on old leaves of Asarum megacalyx

Although the papilionid butterfly Luehdorfia japonica, usually lays eggs on new leaves of the host plant (Asarum sp.; Aristolochiaceae), eggs of the butterfly were frequently found on old leaves of Asarum megacalyx in Suyama, Tokamachi, Niigata prefecture. Larvae hatched on new leaves and those hatched on old leaves did not show significant differences in their survival rate in the field. In laboratory breeding, about 90% of larvae that were fed old leaves survived and developed normally to the pupal stage. Their growth rate, however, was slightly lower than those that were fed new leaves. No nutritional differences were found between the old and new leaves. The reason why oviposition on the old leaves was so frequent and why larvae that hatched on old leaves could survive in the study area is discussed.     

Japanese oak silkmoth feeding preference for and performance on upper-crown and lower-crown leaves

We quantified differences in leaf traits between upper and lower crowns of a deciduous oak, Quercus acutissima, and examined feeding preference, consumption and performance of the Japanese oak silkmoth, Antheraea yamamai, for those leaves. Upper‐crown leaves had significantly smaller area, larger dry mass per area, greater thickness, lower water content, higher nitrogen content and a higher N/C ratio than lower‐crown leaves. When simultaneously offered upper‐crown and lower‐crown leaves, moth larvae consumed a significantly larger amount of the former. However, when fed with either upper‐crown or lower‐crown leaves (no choice), they consumed a significantly larger amount of the latter. Female larvae reared on upper‐crown leaves had a significantly smaller fresh weight, but attained a significantly larger pupal fresh and dry weight, with a significantly higher relative growth rate than those on lower‐crown leaves. Although, like female larvae, male larvae had a significantly smaller fresh weight when reared on upper‐crown leaves, they had a significantly larger value only for pupal dry weight. These results suggest that: (i) larvae ingest a greater amount of lower‐crown leaves to compensate for the lower nitrogen content of the foliage, resulting in having an excess of water because of the higher water content of the foliage; (ii) feeding preference for upper‐crown leaves accords with better performance (with respect to dry pupal weight and relative growth rate) on the foliage; (iii) better performance is explained by a higher nitrogen content and N/C ratio of the upper‐crown foliage; and (iv) the effects of leaf quality on performance differ between sexes.     

Growth and energetics of a trichopteran larva feeding on fresh submerged and terrestrial plants

We studied the growth and assimilation of larvae of Anabolia nervosa, a lotic trichopteran shredder, on diets of fresh tissue of the submerged macrophyte Potamogeton perfoliatus and fresh leaves of the trees Alnus glutinosa and Fagus sylvatica. Fifth-instar larvae were fed these three diets for 23 days (20 May–12 June) in the laboratory. Instantaneous growth rate and gross growth efficiency were almost the same for larvae fed Potamogeton and Alnus, but lower for larvae fed Fagus. The larvae consumed 3 times more fresh Potamogeton than Alnus leaves, but the same amounts in terms of dry mass. The consumption of fresh Fagus was initially twice that of the two other food items but dropped rapidly during the experiment, following the marked seasonal decline of leaf nitrogen content. Allocation patterns of fat and protein differed among food sources. Larvae grown on Alnus accumulated more fat than larvae grown on Potamogeton, while the reverse was true for protein accumulation. The assimilation efficiency based on carbon units was the same (44%) for all three food items and was among the highest reported for shredding caddis larvae. The study demonstrates that fresh tissue of Potamogeton perfoliatus provides a valuable food source to the facultative shredder herbivore Anabolia nervosa.     

Food preference, growth and maturation of Nemurella pictetii (Plecoptera: Nemouridae)

1. The stonefly Nemurella pictetii has a highly variable life cycle and is semi‐ and uni‐, but also plurivoltine in different geographical areas. 2. The influence of the type of food on growth and maturation of larvae was studied in laboratory experiments. Food preference was also assessed. 3. Larvae of N. pictetii are strongly opportunistic feeders utilising a broad range of food sources. However, biofilm was preferred over detritus (conditioned leaves), green algae and animal food. The highly mobile larvae quickly found the preferred food. Larvae fed on biofilm grew and developed significantly faster than larvae fed on conditioned leaves. 4. Larval growth and maturation in experiments as well as in the field differed with available food qualities. Phases of faster growth and maturation corresponded well with maximum availability of biofilm in the field. This contributes to the interpretations of differences in life cycles in the field.     

Experimental simulations of climate change induced mismatch in oak and larval development rates impact indicators of fitness in a declining woodland moth

Consequences of climate change-driven shifts in the relative timing of spring activities of interacting species are insufficiently understood, especially for insects. We use a controlled experiment which simulates a trophic mismatch scenario in which lepidopteran larvae predominately feed on older leaves due to foliage developing faster than larvae growth rates. As a case study our experiment uses Orthosia cerasi, which is a widespread but declining woodland moth whose UK declines appear to be driven by warming temperatures. In the control experiment larvae are fed young oak Quercus robur leaves (bud burst stages six and seven), whilst in the treatment newly emerged larvae are fed young leaves but then gradually transition to feed on older leaves (post bud burst stage seven). We assess impacts on duration of the larval stage, pupal size and overwintering duration and survival. Larvae in the phenological mismatch treatment had a longer larval period, and smaller and lighter pupae. Larval diet did not carry over to influence emergence dates as earlier pupation of control larvae was balanced by an equivalent increase in the duration of the pupal stage. Increased time spent as larvae could increase predation rates from avian predators, whilst slowing the seasonal decline in food availability for those bird species. Reduced pupal size and weight are indicators of lower fecundity in emerging adults. Notably, we find that adults emerging from the mismatch treatment exhibited greater rates of abnormal vestigial wing development, which is likely to further reduce fitness. Trophic mismatches in which caterpillars have reduced availability of young leaves may thus contribute to the population declines observed in many woodland moth species due to increased mortality at larval stages, and adverse effects of early life conditions that reduce the reproductive success of emerging adults.     

Growth and survival of river catfish Mystus nemurus (Cuvier & Valenciennes) larvae fed isocaloric diets with different protein levels during weaning

The growth of river catfish Mystus nemurus (Cuvier & Valenciennes) larvae fed four isocaloric diets (4200 kcal kg^?1) with different protein levels during weaning was determined. Diets containing 45, 50, 55, and 60% protein were formulated by linear programming using amino acid profiles based on that of 2‐day‐old river catfish larvae. Artificial diets were fed to the larvae beginning at day 5 after being initially fed Artemia nauplii for 4 days. The larvae thrived solely on artificial diets from day 8 to day 16. On the other hand, the control larvae were fed Artemia nauplii from day 1 to day 16. Results of the feeding trial showed that growth and survival of M. nemurus larvae given the diet containing 60% protein were high and comparable to those of the larvae given only live food (control). Larvae fed the 55% protein diet had significantly lower growth and survival than the larvae on the control and 60% diets but significantly higher growth and survival rates than did larvae fed with 45 and 50% protein diets. Carcass moisture and total lipids after 16 days of feeding did not differ significantly (P > 0.05), but body protein increased with increasing dietary protein. Body protein of the control larvae was similar to that of larvae given the 60% protein diet.     

Onshore–offshore variations of copepod community in northern South China Sea

Previous studies which have tested the feeding preferences of shredders for fungal species and the food quality of fungi used detritus uniformly colonized by a fungus, which is not the case for decaying leaves in streams. It is not known whether shredders in different development stages exhibit variations in feeding preference and larval performance. This study examined the feeding preferences and the growth of the third and the fifth instars of Pycnopsyche gentilis larvae using fungal-colonized patches and whole leaves, respectively, having different fungal species compositions (Alatospora acuminata, Anguillospora filiformis, Articulospora tetracladia, Tetrachaetum elegans, and all species combined). The aquatic hyphomycetes used were co-dominant on leaves in the stream inhabited by the caddisfly. During 14 d of feeding, the larvae of both instars did not show significant differences in feeding preferences for the patches growing on oak leaves, although the third instar larvae were slightly more selective than the fifth instar larvae. When fed with maple leaves for 18 d, larval growth rates, gross growth efficiencies, and survivorship were not significantly different among the fungal treatments. However, the larval growth of both instars fed with fungal-colonized leaves was always significantly greater than the growth of larvae fed with diets of uncolonized leaves. The third instar larvae grew faster than the fifth instar larvae, but the growth efficiencies of the two instars were similar. These results suggest that P. gentilis larvae exhibit less selectivity in their feeding than other caddisfly shredders that have been examined and that the dominant fungi colonizing leaves in their habitat are similar in palatability and food quality for this shredder. Handling editor: B. Oertli     

Effects of live food and formulated diets on survival, growth and protein content of first-feeding larvae of Plelteobagrus fulvidraco

In recent years, much progress has been made in the rearing of fish larvae fed only artificial diets. A preliminary study was made in an attempt to evaluate the effects of live food and formulated diets on survival, growth and body protein content of first‐feeding larvae of Plelteobagrus fulvidraco. Three test diets varying in protein level were formulated: Feed 1 containing 45% protein, Feed 2 with 50% protein and Feed 3 with 55% protein. Larvae fed live food (newly hatched Artemia, unenriched) were the control. The experiment started 3 days post‐hatch and lasted for 23 days. At the end of the 23‐day trial, survival was best in the control group (65.6%) whereby the final body weight and specific growth rate (SGR) were significantly lower than those in the test feed groups. At the same time, coefficients of variation for SGR and final body weight in the test groups were significantly higher than those in the control. Whole body protein content in all treatments showed a similar tendency during development: significantly higher 3 days post‐hatch, then decreasing significantly, and then increasing unstatistically 10 days post‐hatch. All results suggest that live food is still better for first‐feeding larvae of P. fulvidraco, since live food leads to healthier larvae growth.     

The Association of the Stream Caddisfly Lasiocephala basalis (Kol.) (Trichoptera: Lepidostomatidae) with Wood

A population of the lepidostomatid caddisfly, Lasiocephala basalis, was studied in a third order stream, the Ohe, in Hesse, Germany. L. basalis showed an intimate association with wood debris in all of its aquatic life stages. Larvae exhibited a significant preference for organic substrates such as woody debris, leaves, and submerged alder roots. Gut content analysis revealed leaf material and wood fragments as the dominant larval food items classifying larvae as facultative xylophagous. Larval dominance on wood during spring corresponded to minimal leaf litter abundance. In winter, during periods of high discharge, the most important larval habitat was the submerged alder roots at the stream margin, thus acting as flow refugia. Most pupal cases were attached to submerged logs and roots. In addition, most of the egg masses were found on these two substrates. The role of L. basalis larvae in wood degradation is discussed.