Tachyporus Hypnorum Research Articles

Peculiarities of the development and seasonal dynamics of the activity of epigean beetles of the Polyphaga suborder (Coleoptera) in fields of winter wheat in the conditions of Southern Ukraine

In total, 168 beetle species from 25 families of the suborder Polyphaga have been recorded on winter wheat crops. 116 species (about 20 families) are registered as stratobionts: 14 were dominants, 32 – subdominants and about 70 species were very rare. The main representatives of stratobios were Staphylinidae, Silphidae, Dermestidae, Histeridae, some Elateridae and Scarabaeidae and most Tenebrionidae. Most staphylinids are more numerous in spring (late April – first half of May) and sometimes in summer (especially dominant Tachyporus hypnorum). A high number of Silphidae was noted by mid-May, but decreased in the summer months. Two peaks of abundance are characteristic of Anthicidae, Latridiidae and Cryptophagidae: the smaller in spring (the first half of May) and the maximum in summer (the second half of June – early July). The number of Dermestidae increases gradually from mid-May and reaches maximum from late May to early or mid-June. Among Tenebrionidae, the species of genera Opatrum and Gonocepalum are more numerous in spring than in summer. Crypticus quisquilius were numerous by mid-summer. Among Elateridae, high number of Agriotes sputator was recorded from May to mid-June, and the appearance of Aelosomus rossi was recorded from mid-April, with a peak in the first half of summer. In spring, some Scarabaeidae (some species of Geotrupinae and Pentodon idiota), Histeridae and some species of weevils were more numerous in summer. In years with different meteorological conditions, significant discrepancies were noted in the timing of the rise and fall in the number of many beetles. But smaller differences in the number of specimens are noted between different years in comparision with individual phases of wheat vegetation. Some features of the sex index of beetles (higher during egg laying) and the development of dominant species are briefly considered.

List of Staphylinids of Lagodekhi Reserve with some new records from Sakartvelo (Georgia)

The rove beetles (Coleoptera: Staphylinidae) are one of the most diverse families of beetles comprising more than 63650 species worldwide (Irmler et al. 2018). It is the best studied coleopteran family in Georgia (Herman, 2001; Schülke Smetana, 2015), with more than 750 species recorded (Tarkhnishvili Chaladze, 2019). The first records of Staphylinidae from Lagodekhi were reported by Zhizhilashvili (1941), who recorded 12 species of rove beetles from the reserve: Anotylus hybridus Eppelsheim, 1878 as Oxytelus; Anotylus gibbulus Eppelsheim, 1878 as Oxytelus; Xantholinus variabilis Hochhuth, 1851; Cordalia obscura Gravenhorst; Philonthus parvicornis Gravenhorst, 1802 as P. agilis Gravenhorst; Stenus circularis Gravenhorst, 1802 as S. clavulus Hochhuth; S. cribratus Kiesenwetter, 1850; Tachyporus hypnorum (Fabricius, 1775); Ocypus nitens (Schrank, 1781) as Staphylinus similis Fabricius; Quedius minor Hochhuth, 1849 as Q. distincticolor Roubal; Aleochara intricata Mannerheim; Olophrum caucasicum Fauvel, 1875. The record of Medon bicolor (Olivier, 1795) (as Sunius) in the same paper is erroneous because the species is absent from Georgia. Coiffait (1969) described Quedius grouziacus as a new species from Lagodekhi, however the species was later synonymized with Q. suramensis Epelsheim, 1880 by Solodovnikov (2002). Ushakov (1988) recorded Gauropterus sanguinipes Reitter, 1889, Gyrohypnus angustatus Stephens,1832 and Atrecus affinis (Paykull, 1789) as Baptolinus affinis caucasius Roubal, 1933. Gusarov and Koval (2002) registered Korgella caucasica (Gusarov Koval, 2002; Özdikmen, 2005), as Heinzia. Later Shavrin Khachikov (2019) added Acrolocha amabilis (Heer, 1841) which was new to the staphylinid fauna of Georgia. There have been no other focused studies on the Staphylinidae of Lagodekhi Protected Areas (LPA), though we recognize that there are likely further records in the literature.

Polyphagous predatory rove beetles (Coleoptera: Staphylinidae) induce winged morphs in the pea aphid Acyrthosiphon pisum (Hemiptera: Aphididae)

A number of aphid species have been shown to produce winged dispersal morphs in the presence of natural enemies. Pre- vious studies tested specialized aphid predators such as ladybirds or lacewing larvae. We confronted colonies of pea aphids with the polyphagous rove beetles, Drusilla canaliculata and Tachyporus hypnorum. For both predators we found that the percentage of winged morphs increased in predator-attacked pea aphid colonies compared to a control. The behaviour of the two rove beetles spe- cies was noticeably different. D. canaliculata mostly foraged on the ground and rarely on the plant, while T. hypnorum was almost exclusively observed on the plants, causing a higher number of aphids to drop to the ground, which resulted in a stronger increase in winged morph production. Our results clearly show that not only monophagous aphid predators but also more polyphagous insect predators, which include aphids in their diet, can induce aphids to produce winged morphs.

Farming system and habitat structure effects on rove beetles (Coleoptera: Staphylinidae) assembly in Central European apple and pear orchards

In field experiments over a period of five years the effects of farming systems and habitat structure were investigated on staphylinid assembly in Central European apple and pear orchards. The investigated farms were placed in three different geographical regions with different environmental conditions (agricultural lowland environment, regularly flooded area and woodland area of medium height mountains). During the survey, a total number of 6,706 individuals belonging to 247 species were collected with pitfall traps. The most common species were: Dinaraea angustula, Omalium caesum, Drusilla canaliculata, Oxypoda abdominale, Philonthus nitidulus, Dexiogya corticina, Xantholinus linearis, X. longiventris, Aleochara bipustulata, Mocyta orbata, Oligota pumilio, Platydracus stercorarius, Olophrum assimile, Tachyporus hypnorum, T. nitidulus and Ocypus olens. The most characteristic species in conventionally treated orchards with sandy soil were: Philonthuss nitidulus, Tachyporus hypnorum, and Mocyta orbata, while species to be found in the same regions, but frequent in abandoned orchards as well were: Omalium caesum, Oxypoda abdominale, Xantholinus linearis and Drusilla canaliculata. The species Dinaraea angustula, Oligota pumilio, Dexiogya corticina, Xantholinus longiventris, Tachyporus nitidulus and Ocypus olens have a different level of preferences towards the conventionally treated orchards in clay soil. The species composition of the staphylinid fauna in apple and pear orchards could not be considered uniform. The environmental conditions and the soil together have a significant influence upon the richness of species, and the cumulative effects of these factors can modify even the dominance structures of the communities.

Dominance, activity density and prey preferences of rove beetles (Coleoptera:Staphylinidae) in conventionally treated Hungarian agro-ecosystems

Field experiments were conducted to investigate the mechanism underlying patterns of the rove beetle populations in apple and pear orchards (1998-2002) and winter wheat (2006-2007) in Hungary following treatment with broad-spectrum insecticide. The capacity of predatory staphylinid species to feed on cereal pests was measured, with six species tested in petri dishes, in the laboratory at room temperature. Almost 23% of the Hungarian and 13% of the European staphylinid fauna are represented in the investigated agro-ecosystems. In orchards, 5236 individuals, belonging to 253 species, were collected. The most widely occurring were Omalium caesum Gravenhorst, Drusilla canaliculata (F.), Dinaraea angustula (Gyllenhal), Palporus nitidulus (F.), Xantholinus. longiventris (Olivier), X. linearis (Olivier) and Aleochara bipustulata (L.). In winter wheat, 798 individuals and 20 species were collected, the most frequent were Staphylinus caesareus Cederh, Tachyporus hypnorum (F.), Philonthus cognatus (Stephens), Aloconota gregaria (Erichson), Tachyporus chrysomelinus (L.) and T. obtusus (L.). Species composition differed by crop (apple, pear and wheat), soil composition and surrounding habitat. Species diversity was also influenced by these parameters. In wheat, one acute change in species composition was observed with the decline of Tachyporus spp., which occurred equally across all farms. The consumption rate of prey by the dominant species occurring in wheat ecosystems was relatively high; however, we did not offer any fungal food to compare with insects' prey.

Effects of maternal diet quality on offspring performance in the rove beetle Tachyporus hypnorum

Abstract1. The reproductive output of an individual is known to be influenced by diet quality, but the quality of the parent's diet can also influence the performance of the offspring. Dietary maternal effects may interact with the effects of the offspring's diet to produce a variety of response patterns.2. Maternal effects were investigated in a polyphagous predator, the rove beetleTachyporus hypnorum, using three single‐species diets: two low‐quality diets consisting of the aphidsSitobion avenaeandRhopalosiphum padi, and the high‐quality controlDrosophila melanogasterdiet. Offspring of females fed these diets were raised on the same monotypic diets and allowed to reproduce. Several fitness parameters were measured to indicate possible maternal effects in both F1 and F2 generations.3. Maternal diet effects in F1 were found in egg size, hatching success, time to hatching, larval development time, larval survival, and sex ratio. Both aphid diets resulted in smaller eggs. A diet ofR. padiresulted in reduced hatching success, longer time spent in the egg stage, and a female‐biased sex ratio. A maternal diet ofR. padialso prolonged larval development onS. avenaediet, while a maternal diet ofS. avenaedecreased survival on theR. padidiet. These effects were independent of egg size.4. A maternal diet ofR. padienhanced the survival of F1 larvae raised on the same diet. Developmental selection operating through a high egg mortality may be the explanation for this seemingly positive effect.5. Sitobion avenaealone caused a significant reduction in the hatching success of F2 eggs, thus revealing grandmaternal effects.6. The prediction that polyphagous predators are less likely to evolve adaptive maternal effects is supported by the fact that none of the documented maternal effects could be interpreted as adaptive.

Quality of two aphid species (Rhopalosiphum padi and Sitobion avenae) as food for the generalist predator Tachyporus hypnorum (Col., Staphylinidae)

Abstract: The quality of two aphid species (Rhopalosiphum padi and Sitobion avenae) as food for the staphylinid generalist predator Tachyporus hypnorum was investigated. Fruit flies (Drosophila melanogaster) were used as prey for comparison. T. hypnorum has been reported to prey on aphids, to consume large quantities and to show a high preference for aphids. This study showed that compared with fruit flies aphids are not high‐quality prey for neither adult females nor larvae of T. hypnorum. Larvae were less able to utilize aphids than adult females. Reproduction was affected by both aphid species; a diet of S. avenae reduced fecundity, and a diet of R. padi reduced egg hatching success and prolonged the time spent in the egg stage compared with a fruit fly diet. For the T. hypnorum larvae pure diets of both S. avenae and R. padi resulted in high larval mortality. Overall ranking of the three prey types based on several fitness parameters differed between larvae and adults. The adult fitness parameters gave rather conflicting rankings of all three prey types though the two aphid species were of approximately the same overall value, whereas the larval fitness parameters gave identical rankings: D. melanogaster > S. avenae > R. padi. In the larval stage survival was greatly reduced by both aphid diets, while this was not the case for the adult females.

Species Composition of Ground Dwelling Staphylinid (Coleoptera: Staphylinidae) Communities in Apple and Pear Orchards in Hungary

Species richness and composition of Staphylinidae communities were investigated at ground level when differently treated with pesticides and in abandoned apple and pear orchards in Hungary. Altogether 6099 individuals were collected belonging to 241 staphylinid species. 233 have been identified to species level and 8 staphylinid taxa were determined up to generic level. More than 20% of the Hungarian staphylinid fauna was represented in the orchards. The similarity (Jaccard index) between apple and pear orchards at ground level were 54%. The species richness in each orchard varied between 23 and 100 species. The most widely occurring species in orchard ground level were: Dinaraea angustula, Palporus nitidulus, Tachyporus hypnorum, Sphenoma abdominale, Omalium caesum, Philonthus carbonarius, Drusilla canaliculata, Sepedophilus marshami, Mocyta orbata, Coprochara bipustulata, Mocyta fungi, Hyponygrus angustatus, Purrolinus laeticeps, Paraphallus linearis, Omalium cursor, Heterothops dissimilis and Atheta crassicornis.

Capacity of Bembidion lampros and Tachyporus hypnorum to survive periods of starvation in early spring

AbstractThe capacity of the polyphagous predators Bembidion lampros Herbst (Coleoptera; Carabidae) and Tachyporus hypnorum F. (Coleoptera; Staphylinidae) to survive starvation in early spring was investigated. The two species are of similar size and live in the same habitat. They have similar life cycles; where adults emerge in autumn, hibernate during winter and disperse during spring into arable fields where they reproduce and then die. Both species showed an ability to survive long periods of starvation after hibernation. However, B. lampros could live without food several weeks longer than T. hypnorum.Fat content was measured to estimate the energy reserves of beetles in the field. The fat content of B. lampros was at a constant level of 23% both when fed ad libitum in the laboratory and when collected in the field during spring. The fat content of B. lampros was reduced to a level of 7% when they died by starvation. Fat content of T. hypnorum was more variable both when fed ad libitum in the laboratory (17–33%), when collected in the field during the spring (20—26%) and when they died by starvation (10–20%).Neither the mean longevity of starved beetles nor the fat content of specimens collected in the field indicated that the beetles suffered high mortality due to a food shortage in early spring before movement into arable fields.

The timing of dispersal of the predatory beetles Bembidion lampros and Tachyporus hypnorum from hibernating sites into arable fields

The timing of dispersal of the predatory beetles <i>Bembidion lampros</i> and <i>Tachyporus hypnorum</i> from hibernating sites into arable fields

Fecundity and juvenile survival of Bembidion lampros and Tachyporus hypnorum

AbstractFecundity and development from first instar larvae to adult beetles were studied for Bembidion lampros Herbst (Coleoptera; Carabidae) and Tachyporus hypnorum F. (Coleoptera; Staphylinidae). Both species reproduce in arable fields, where they are known to contribute to the natural control of cereal aphids. They are univoltine and have similar life cycles and development times. T. hypnorum females laid approximately 3 times more eggs than B. lampros females. Relative lifetime fecundity of B. lampros was very low with an average of 10 eggs per female. Based on the time where half of the populations had dispersed from the overwintering sites into an arable field B. lampros started egg‐lay 100°D (°C&gt;9) and T. hypnorum 200°D (°C&gt;3) after dispersal. Mortality in the juvenile stages was found to be an important factor in the population dynamics of both B. lampros and T. hypnorum. The survival from first instar larvae to adults was on average 34% for B. lampros independent of soil type, 21% for T. hypnorum developed in sandy soil and 49% when developed in clayey soil under semi‐field conditions. Enlargement of B. lampros and T. hypnorum populations to increase the natural control of aphids during their establishment in cereal fields may be possible if the conditions for juvenile development are improved.

The effect of different farming systems on epigeic arthropods: a five-year study on the rove beetle fauna (Coleoptera: Staphylinidae) of winter wheat

The susceptibility of rove beetles to extensification practices in agriculture was studied in four farming systems on the same farm for a period of five years. The systems differed in application of fertilizer and pesticides in methods of soil cultivation and in crop rotation. The most common staphylinid species ( Tachyporus hypnorum, Oxytelus inustus, Lesteva longelytrata, Philonthus fuscipennis) were the same in all farming systems, but total faunal composition was different. Species richness and diversity were highest with reduced tillage and fewer pesticide applications. This was the result of an increased (but still tolerable) weed density which probably caused more favourable microclimatic conditions. Moreover, some species were negatively affected by the use of a plough and the abundance and biomass of potential prey is considered to be higher on unploughed plots. A reduction in the use of insecticides alone led to an increase of the abundance of a few of the most common species, but had no positive effect on species richness. The treatment “no fertilization” led to sparse crops with unfavourable microclimate. In this case, population density and the number of species of the rove beetle fauna decreased even when no pesticides were applied.

Adult polyphagous coleopterans overwintering in cereal boundaries: winter mortality and susceptibility to the entomopathogenic fungus Beauveria bassiana

Autumn-collected Bembidion lampros and Agonum dorsale were kept outdoors under semi field conditions to determine winter mortality. On three occasions (autumn, mid-winter and late winter) sub-samples of the population were incubated in the laboratory at room temperature and mortality was recorded. Generally the mortality was low in autumn and mid-winter, not exceeding 5%. A more pronounced post-winter mortality of up to 30% was observed at the end of hibernation. Only a negligible number were infected by the entomopathogenic fungi Beauveria bassiana and Paecilomyces farinosus. Infection experiments with B. bassiana isolates from Sitona lineatus, Tachyporus hypnorum and three species of ground beetles showed a similarly low susceptibility of B. lampros and A. dorsale to B. bassiana and, although Tachyporus spp. showed a distinct mycophagy and a significantly higher mortality, this could not be related to mycosis.

Temperature dependent winter survival of Bembidion lampros and Tachyporus hypnorum

Wintering survival of the predatory beetles Bembidion lampros and Tachyporus hypnorum was tested under field conditions with manipulated periods of constant frost. Survival of both species was influenced negatively by short frost periods during an otherwise mild winter. Exposure to 2 weeks of frost during a mild winter reduced survival below 10%. Survival during a harsh winter with constant subzero temperature was high for both species. Overwintering survival was also tested experimentally under different temperature regimes in the laboratory. Survival of B. lampros at fluctuating temperatures between −2 °C and +6 °C, was lower when the temperature fluctuated on a weekly basis than on a daily basis. Survival of T. hypnorum was severely affected by fluctuating temperatures around 0 °Cindependent of the frequency. Winter survival was generally higher for B. lampros than T. hypnorum under equivalent temperature conditions both in the field and in the laboratory. Super cooling point (SCP) and weight changes were measured on individual specimens during overwintering under field conditions. SCP for B. lampros decreased as the winter became harsher while SCP for T. hypnorum seemed to be constant under the same conditions. At the end of the winter SCP for B. lampros increased dramatically. Weight changes of individual specimens were constantly low for both species during a harsh winter. Mean weight changes of B. lampros and T. hypnorum during overwintering was followed under different temperature regimes. Mean weight changes after the winter did generally not explain winter mortality.

The toxicity of dimethoate to predatory coleoptera: Developing an approach to risk analysis for broad-spectrum pesticides

Topical toxicity bioassays were undertaken with the organophosphate compound dimethoate, O, O-dimethyl S-methylcarbamoylmethyl phosphorodithioate, against six species of predatory Coleoptera that are recognized predators of cereal aphids: the staphylinid Tachyporus hypnorum, the coccinellid Coccinella septempunctata and the carabids Demetrias atricapillus, Trechus quadristriatus, Bembidion obtusum and Nebria brevicollis. LD50 values for formulated dimethoate, diluted in water, varied between 3.4 and 98.8 ng a.i. insect−1 and 1.45 and 18.20 μg a.i. g−1 body weight. These values were similar to those obtained in another study by Wiles and Jepson (1992) for the pyrethroid insecticide deltamethrin, (S)-alphacyano-3-phenoxybenzyl (1R)-cis-3-(2,2-dibromovinyl)-2,2,-dimethylcyclopropanecarboxylate. Hazard ratios were calculated for dimethoate and deltamethrin by dividing recommended field mass application rate in g a.i. ha−1 by LD50 in μg a.i. insect−1: this gave an indication of potential direct exposure hazard. The range of values for dimethoate (3,441 to 100,000) were well in excess of those for deltamethrin (28.6 to 500) because of its greater field application rate (340 g a.i. ha−1 compared with 6.25 g ai ha−1). LT50s were determined for adult C. septempunctata exposed to wheat leaves treated with either dimethoate or deltamethrin at full or half field rate within in-situ bioassays. At both rates, the dimethoate LT50s were shorter, ranging at full rate from 0.06 to 7.70 h, between 2 and 96 h after treatment, compared with 1.04 to 20.89 h after the same time intervals for deltamethrin. At half-field rate, the equivalent LT50 ranges were 0.52 to 13.65 h for dimethoate and 3.75 to 31.76 h for deltamethrin. The relative toxicities of the two insecticides, expressed as the ratio of log (x+1) LT50 deltamethrin:dimethoate, narrowed greatly between 2 and 24 h, especially in the full rate treatment, indicating a more rapid loss of dimethoate than deltamethrin from foliage in the field shortly after spray application. The ecotoxicological consequences of exposure to dimethoate and deltamethrin are compared relative to their differing mass application rates, physicochemical properties and environmental fate. The role and value of laboratory-based toxicological testing within risk analysis procedures is discussed.

Substrate-mediated toxicity of deltamethrin residues to beneficial invertebrates: Estimation of toxicity factors to aid risk assessment

Laboratory bioassays were carried out to determine the toxicity of residues of the synthetic pyrethroid insecticide, deltamethrin ((S)-α-cyano-3-phenoxybenzyl (1R)-cis-3-(2,2-dibromovinyl)-2,2-dimethylcyclopropanecarboxylate) to a range of beneficial invertebrates exposed to treated wheat foliage, sandy loam soil, and glass surfaces. The test invertebrates represented a range of predators and a parasitoid that inhabit the foliage and grounds layers of temperate cereal crops, i.e., Pterostichus melanarius (Illiger), Nebria brevicollis (F.), Demetrias atricapillus (L.) and Bembidion obtusum (Serville) (Coleoptera: Carabidae), Tachyporus hypnorum (F.) (Coleoptera: Staphylinidae), Coccinella septempunctata (L.) (Coleoptera: Coccinellidae) adults (A) and larvae (L), Episyrphus balteatus (Degeer) (Diptera: Syrphidae), and Aphidius rhopalosiphi (De Stefani-Perez) (Hymenoptera: Braconidae). In 2 h flag leaf exposure bioassays, the LD50 values varied from 0.4 g ai/ha to >50 g ai/ha. The susceptibility ranking, from most to least susceptible, was C. septempunctata (L) > T. hypnorum > C. septempunctata (A) > E. balteatus > A. rhopalosiphi > D. atricapillus. On soil, the LD50 values were 52.8 g ai/ha for T. hypnorum and 97.8 g ai/ha for C. septempunctata (A) after 2 h exposure. This period of exposure was, however, found to be of insufficient duration to separate the susceptibilities of the other test species adequately, and therefore 72 h exposure bioassays were also carried out. The 72 h LD50 values varied between 4.2 g ai/ha and 267 g ai/ha. The susceptibility ranking, from most to least susceptible, was T. hypnorum > B. obtusum > C. septempunctata (A) > P. melanarius > N. brevicollis > D. atricapillus. In 2 h glass bioassays the LD50 range was 1.2 g ai/ha to >37 g ai/ha and the susceptibility ranking was T. hypnorum > C. septempunctata (A) > N. brevicollis, and D. atricapillus. Residual toxicities in the different 2 h exposure bioassays were compared for T. hypnorum and C. septempunctata (A) by iterating sequences of lethal dose ratios between LD10 and LD90 from the dose-response statistics for each respective pair of substrates. The mean ratios were termed “toxicity factors” (Tf). Tf values comparing glass and flag leaf assays, were 0.98 and 1.23, respectively for T. hypnorum and C. septempunctata (A), indicating that the toxicity of fresh deltamethrin residues to both species was similar on these surfaces. Tf values comparing either glass or flag leaf and soil were however in the range of 50–60 for T. hypnorum and C. septempunctata (A), indicating much lower effects on soil. Estimates of the bioavailable half-life on leaf and soil, obtained from in situ bioassays, indicated that effects in the field may vary two- to threefold as a result of differences in the duration of toxicity on these substrates. Overall, T. hypnorum could be at more than 150 times greater risk on leaf compared to soil surfaces. The potential for extrapolating laboratory toxicity data to the field is discussed.

Structural Features of Field Boundaries Which Influence the Overwintering Densities of Beneficial Arthropod Predators

Vegetation cover was manipulated within enclosures on a field boundary in southern England to test experimentally the effect on the overwintering of Tachyporus hypnorum and Demetrias atricapillus populations, species that use grassy boundaries of arable fields as refugia during winter. Winter survival was lowest for beetles enclosed on bare earth and highest for those enclosed on tussocks of Dactylis glomerata. The contrast in structural complexity of the experimental treatments caused a 44%, 43% and 36% variation in the final densities of beetles during three successive winters. The densities of T. hypnorum on adjacent field boundaries were estimated from the composition of their vegetation cover and the survival rates of the beetles on different treatments

The susceptibility of a cereal aphid pest and its natural enemies to Deltamethrin

AbstractThe intrinsic toxicity of deltamethrin to the grain aphid Sitobion avenae (F.) (Hemiptera: Aphididae) and a range of its important natural enemies was determined by laboratory topical bioassay. The natural enemies included polyphagous predators such as Pterostichus melanarius (Illiger), Harpalus rufipes (Degeer), Nebria brevicollis (F.), Agonum dorsale (Pont.), Demetrias atricapillus (L.), Trechus quadristriatus (Schrank), Bembidion obtusum (Serville), and B. lampros (Herbst.) (Coleoptera: Carabidae), Tachyporus hypnorum (F.) (Coleoptera: Staphylinidae) and Erigone atra (Blackwall) (Araneae: Linyphiidae), as well as the aphid‐specific ladybird Coccinella septempunctata (L.) (Coleoptera: Coccinellidae). Dose–response relationships were compared between species by probit analysis and maximum likelihood procedures to determine trends of susceptibility, measured in terms of ng a.i. arthropod−1 and μg a.i. g−1 body weight. The range of LD50 values varied between 0.8 and 232 ng arthropod−1 and 0.76 and 66.17 μg g−1 body weight for the species tested. The linyphiid spider E. atra (♀) was the most intrinsically susceptible species and had the narrowest tolerance distribution of the predators tested, whereas the small carabid beetle D. atricapillus was the least intrinsically susceptible predator species. There were significant differences in susceptibility between species of different orders, i.e. the Araneae, Hemiptera and Coleoptera. Differences within the Coleoptera were closely related to body weight, with the exception of the carabid beetle D. atricapillus, which seemed to be tolerant to deltamethrin. Knockdown time studies indicated that D. atricapillus had a higher survival rate after being knocked down than other species of predator. Aphid susceptibility per unit body weight was not significantly different from that of the predators. The aphid did, however, demonstrate a broader tolerance distribution than most of the predators, which may be related to its herbivorous nature. The use of laboratory susceptibility data to determine selectivity and to predict pesticide hazard is discussed.

Abiotic and biotic factors influencing the winter distribution of predatory insects.

Various environmental factors were investigated to analyse those involved in successful overwintering and possibly overwintering site selection for Tachyporus hypnorum and Demetrias atricapillus, both important coleopteran predators of cereal aphids. The results of the study indicated food supply to be important for both predator species during the winter period, although the role of biotic factors in site selection in the autumn could not be clearly demonstrated. The winter distribution of the two species could, however, be explained well in terms of abiotic factors. It is suggested that these and other similar predator species have well-defined overwintering requirements and that these can be exploited in the management of field boundary habitats.

Mycophagy as a factor limiting predation of aphids (Hemiptera: Aphididae) by staphylinid beetles (Coleoptera: Staphylinidae) in cereals

AbstractPrevious work demonstrated the potential of the staphylinidsTachyporus hypnorum(Fabricius),T. chrysomelinus(Linnaeus),T. obtusus(Linnaeus) andPhilonthus cognatus(Stephens) to feed on the grain aphid,Sitobion avenae(Fabricius). However, gut dissection and observations of foraging behaviour showed that mycophagy could be a factor influencing the potential ofTachyporusspp. to control aphids. The main fungal material detected in the guts ofTachyporusspp. was spores (conidia) ofErysiphespp. (powdery mildews). In the present study, numbers of conidia (pustules of mildew on leaf-sections) were offered with aphids in food-choice experiments to test how fungal food affected feeding on aphids by these staphylinids. An index of food preference was calculated for each species, sex and for two age classes of larvae, based on the number of conidia and aphids remaining after feeding. Results showed a preference for mildew conidia byT. hypnorum, no preference byT. chrysomelinusandTachyporusspp. larvae and a preference for aphids byT. obtususandP. cognatus(adults and larvae). Food-preferences compared well with dietary composition in recent studies of field collected staphylinids. Futhermore, a functional response was detected to increasing numbers of mildew conidia presented (in mildew only consumption-rate experiments) and to the increase in total food density in food-choice experiments. Mycophagy limited aphid predation and explained the numerical response of staphylinid beetles to areas of cereals with high aphid densities, whilst, in other studies, the proportion of aphids eaten by those beetles did not increase.