Density dependent host mortality in the interaction between the solitary endoparasitoid Aphidius colemani (Aphidiidae), and its host, the green peach aphid Myzus persicae, was examined on greenhouse peppers. The experimental approach attempted to eliminate spatial interdependence in the relationship between host density and host mortality by using different plants to measure parasitism at different spatial scales. Increasing host density at the plant scale caused a significant increase in the proportion of host mortality. However, at the shoot and leaf scale, increasing host density caused a significant decrease in host mortality. This may be one of the first experimental demonstrations of a switch from inverse to direct density dependence. The pattern is assumed to be a result of searching parasitoids using different cues at different spatial scales.
Haemadipsid leeches are among the most successful terrestrial invertebrates in Bornean rainforests. They are very common ectoparasites of vertebrates, and their abundance has facilitated the conduction of numerous projects in the fields of ecology, zoogeography and taxonomy. We undertook research on two species inhabiting lowland dipterocarp forest, Haemadipsa picta Moore, 1929 and Haemadipsa subagilis (Moore, 1929), in order to address the following questions: (a) is there a difference in leech abundance between trails and off-trails?; (b) is ambush location dependent on specimen size or is species-specific?; (c) is intra- and interspecific competition limited by differences in foraging behaviours or vertical niche partitioning? Our results clearly show that H. picta is more abundant on trails than on off-trails and is vertically dispersed within the understory; the size of a specimen is strongly correlated with plant height. Haemadipsa subagilis was found not to exhibit such patterns. We suggest a possible lowering of interspecific competition between these species as a result of: (i) size-dependent dispersion of H. picta (together with reduction of intraspecific competition); and (ii) habitat specialisation of H. subagilis. Moreover, we provide new observations on their foraging behaviour., Piotr Gąsiorek, Hanna Różycka., and Obsahuje bibliografii
The food remains of Neomys fodiens (particularly trichopteran larvae, Gastropoda and Amphibia) found on the banks of ponds and small creeks in Lower Austria are described. Characteristic bite marks, the manner of opening the cases and shells, as well as data on feeding patterns are presented. Food caches mainly consisted of caddis fly larvae and snails, but also contained non-palatable items which shrews apparently had confused with real prey and retrieved. The composition of the caches varied seasonally, showing a marked mid-summer decline and a shift in the proportion of Trichoptera and Mollusca in late summer and autumn. Shrews employed particular methods when breaking snail shells and opening caddis fly cases, and in the consumption of vertebrate carcasses.
The foraging behaviour of individual females of Aphidius uzbekistanicus Luzhetski (Hymenoptera: Aphidiidae) on oat plants with one colony of the grain aphid Sitobion avenae F. (Homoptera: Aphididae) was examined in laboratory experiments. Patch time allocation was analysed under semi-natural conditions when individual hyperparasitoid females, Alloxysta victrix Westwood (Hymenoptera: Alloxystidae) or their volatiles 6-methyl-5-hepten-2-one or a mixture of iridoid substances soaked on vermiculite dummies were present simultaneously. Patch residence times of foraging primary parasitoid females were significantly reduced in all analysed treatment groups. Attack numbers on aphids and resulting aphid mummies were also significantly reduced. The presence of hyperparasitoids or their volatiles had no influence on the proportion of time spent engaged in different behaviour by the primary parasitoid. After encounters with hyperparasitoid females or vermiculite dispensers, which had been soaked with the synthetical iridoids, A.uzbekistanicus females changed their behaviour more frequently, and they left the aphid colony at a higher rate than in the controls, where dispensers had been soaked with only pure pentane. The identification of the associated iridoid substances, produced in the hyperparasitoid mandibular glands, is briefly described and their biological significance is discussed.
The research on pre-diapause feeding of C. septempunctata L. adults was carried out from 1998 to 2002 in the Tiber Valley, in the Botanical Garden of Perugia University, and in the Sibillini Mountains National Park (Central Italy). The species reproduces in spring feeding mostly on aphids infesting Graminaceae. In the second half of June, newly emerged adults have various migratory behaviours. Some of them remain in the valley while some leave the cereals and fly to other crops, where they feed both on 15 aphid species (e.g., Aphis gossypii Glov. on melon, Aphis fabae Scop. on sugarbeet), and also on pollens of wild plants such as Carduus nutans L., and fungi spores. However, most of the adults migrate to mountain pastures to find different food sources. During this migration, strong south-western storms often force the ladybirds to shelter in urban habitats. When the sunny weather returns again, due to the mistral (north-western wind), the adults continue the flight in swarms to mountain areas. In 1999, on Mt. Vettore (2478 m) we witnessed a "shower" of ladybirds, some of which hid in the turf. When reaching high altitude locations still covered with snow (Lake Pilato, 1940 m, on Mt. Vettore), the adults, exhausted by the long flight, usually remain motionless on the snow. Due to the warming of the sun they sink to a depth of 5-6 cm, so that they remain trapped in the frozen snow during the night. At this site C. septempunctata was found together with Vibidia duodecimguttata (Poda) and Leptinotarsa decemlineata (Say). We investigated the gut content of adults from this location. After aggregation, the hungry adults disperse to flowering plants at lower elevations where they feed on 8 aphid species (e.g. broom aphid) and pollens of several plants (e.g., Laserpitium garganicum Tem., Centaurea rupestris L., Cachrys ferulacea L. The first mating was observed on broom. At "Pian Grande" location, adults were found in crop fields (lentil, mustard) and wild pastures (cornflower, gentian) mating and feeding on aphids, pollens, nectar and fungal spores. Haymaking forces ladybirds to move towards higher locations in search of food. Echinops ritro L., Eryngium amethystinum L., Carlina acaulis L., Cirsium eriophorum (L.), Galium verum L. and Euphorbia cyparissias L. were major food sources at 1800 m altitude. Gut content of C. septempunctata adults showed that pre-diapause diet consisted of aphids, pollen of Compositae and Umbelliferae, and spores of fungi (e.g., Alternaria spp., Cladosporium spp.). There was no statistical difference between the number of adults containing remains of aphids, fungal spores, and pollens. We found four significant correlations between the different food sources observed. In August some adults stopped feeding and in diapause condition sheltered under stones and among leaves or seed capsules of plants where they had fed. Others migrated to nearby woods and aggregated between juniper needles.
The aim of this study was to clarify the diet of Ceratomegilla notata (Laicharting), a common species in different mountain habitats of the Palearctic region. In Italy it is found only in alpine ecosystems between 800-1700 m. In these areas, up to 1200 m, various crops (e.g., maize, potatoes) are present. The high meadows are cut for hay. From 2002 to 2003 investigations on the foraging behaviour of this ladybird were carried out in mountain habitats (six near Villabassa, in Bolzano province, and six near Soraga, in Trento province) and in the "Paradisia" Botanic Garden (Gran Paradiso National Park). C. notata adults and larvae were found on the flowering plants, especially those infested by aphids. The study of their diet was done taking random D-Vac samples of 20 adults and 20 larvae/habitat every 15 days, between July and September. The influence of the haymaking on C. notata populations was also evaluated.
In agricultural fields the ladybirds prey on Rhopalosiphum maidis (Fitch), R. padi (L.) on maize and on Acyrthosiphon pisum (Harris) and Therioaphis luteola (Born.) on Trifolium pratense L. In the natural pastures, adults and larvae feed on Cavariella theobaldi G. & B. found on Heracleum sphondylium (Umbelliferae), Sitobion avenae L. on Avena sativa L., Megoura viciae (B.) and A. pisum on Vicia cracca L., Uroleucon jaceae (L.) on Cirsium arvense Scop., U. cichorii (Koch) on Hypochaeris radicata L. and Macrosiphum weberi Born. on Scabiosa sp. A study of the gut contents revealed the presence of aphids, Umbelliferae pollens and spores of fungi (e.g., Alternaria spp., Helminthosporium spp., Puccinia spp.). Statistically significant associations between different food sources were more frequent for adults than for larvae in both 2002 and 2003. Thrips are an important prey of this ladybird in the absence of aphids. C. notata is an important aphidophagous species in Alpine habitats.