The community of predators within agroecosystems has the potential to restrict aphid populations, especially early in the season before exponential increases in density and prior to the arrival of specialist natural enemies. Although direct observations of predation, laboratory feeding trials and manipulative field studies have been used to estimate levels of biological control exerted by different species (or potentially negative interactions between them), it is often difficult to extrapolate results to naturally occurring interactions in the field.
Over 100 investigations have utilized gut-content analysis to estimate aphid predation rates by predators. Throughout the last century, gut dissection, which enables the visual identification of aphid body parts, has been used in over 50% of studies although accurate identification and quantification of predation is difficult. Other techniques have included radio-labelling of prey, dissection of faecal samples, electrophoresis, stable isotope analysis and use of polyclonal antisera. In recent studies of invertebrate predation, monoclonal antibodies have been the most frequently applied technique but advances in molecular biology have enabled the detection of species-specific DNA sequences. The use of these applications to quantify predation by aphidophagous predators will be reviewed, with emphasis on potential sources of error and difficulties of quantitative interpretation. Despite the considerable focus currently directed towards molecular approaches, antibody-based techniques are likely to remain an important tool for studying predation rates of pests in the field, especially when antibodies have already been developed. However, the study of multiple predation events within complex generalist predator food webs is only likely through the detection of species-specific DNA sequences using molecular techniques.

Insect genital characters are extensively used in species level taxonomy, and their value in species delimitation is great. Based on the lock-and-key hypothesis and that genital differences function as a mechanical isolation system between species, the value of genital characters has been thought to be superior to non-genital characters. Although geographical and other kind of intraspecific variation of genitalia is often assumed very moderate, its real extent is insufficiently investigated. We examined patterns of morphological variation in the male genitalia of the tortricid moth Pammene luedersiana, using geometric morphometric tools including thin-plate spline deformation grids, and found significant variation. This variation is continuous both within and between populations. No systematic shape variation was observed between populations, but genital size showed some geographic variability. The results suggest that genital morphology is not constant and should therefore be used with caution in lepidopteran taxonomy.

Responsiveness of Lepidoptera phenology to climate has been detected in a number of species during the current trend in global warming. There is still a question of whether climate signals would be evident in historical data. In this paper we examine the climatic response of 155 species of moths and butterflies collected during the period 1866-1884 in Wiltshire, southern England. In general, species responded to increased temperature in the previous October by delayed appearance and to increased temperature in the current spring by advanced appearance. Thus, differential changes in temperatures of the autumn and spring could well affect changes in the relative pattern of the phenology of species. Attributes influencing the species' ecology were examined to see if they influenced temperature responsiveness. In general, few consistent effects emerged, though responsiveness to climate was found to be greater for species eclosing later in the year, specifically to the previous autumn temperatures, and to hibernal environment, increasingly for species less exposed to air temperatures. These findings warn against expecting simple responses to climate warming.

Females of the parasitoid wasp Dinocampus coccinellae are known to parasitise both male and female coccinellid hosts. It is suggested that female hosts provide more resources for developing wasp larvae because they tend to be larger than male hosts, and female coccinellids have a much greater food intake than males. Thus the wasp's lifetime reproductive success should be increased by ovipositing preferentially in female rather than male hosts when given a choice. Laboratory experiments, using Coccinella septempunctata as a host, show that such a preference does exist. Wasps preferentially oviposit in females, and this preference is not simply a result of the larger mean size of females compared to males. These results corroborate higher rates of prevalence in female compared to male hosts reported previously.

The predation rate of the polyphagous predator Macrolophus pygmaeus (Rambur) when offered two aphid species, Myzus persicae (Sulzer) and Macrosiphum euphorbiae (Thomas), was investigated. Equal or unequal numbers of nymphs of each instar of the aphids were offered to the predator alone or together. Aphids were placed on an eggplant leaf, together with a fifth instar nymph of the predator in a plastic Petri dish and kept in growth cabinets at 25°C, 65 ± 5% r.h., and a 16L : 8D photoperiod. The predation rate of M. pygmaeus was always higher on M. persicae than on M. euphorbiae. However, biomass consumption was highest when instars of M. euphorbiae were offered in unequal numbers. The predator showed a strong preference and higher biomass consumption of first and second instar M. persicae. In tests where M. euphorbiae was the prey, preference and biomass consumption were almost always higher for the first instar. Therefore, first and second instar M. persicae and first instar M. euphorbiae provide optimal prey for M. pygmaeus. The implication of the prey preference shown by M. pygmaeus for the biological control of these two aphid species is discussed.

The aim of the present study was to determine the factors that are involved in termination of a non-diapause type of ovarian arrest in the adult macropterous females of a flightless bug, Pyrrhocoris apterus (L.), reared under a long-day (18L : 6D) photoperiod. Application of an active analogue of juvenile hormone, methoprene, to adult macropterous females kept under the above conditions induced precocious termination of ovarian arrest and shortened the length of the pre-oviposition period. The results indicate that a temporary ovarian arrest in spontaneously fasting long-day macropterous females results from a deficiency of juvenile hormone. The length of the pre-oviposition period was shortened and ovarian arrest terminated also by de-alation, high temperature and by a prolonged period of starvation. Mating of long-day macropterous females with reproductively active males had no effect on the length of the pre-oviposition period. There was a relationship between the length of the starvation period and the post-feeding pre-oviposition period. The longer the starvation period, the shorter the period from when food was supplied to first oviposition. The results indicate that depletion of the fat body reserves resulting from prolonged fasting, followed by resumption of food intake are pre-requisites for full activation of the corpus allatum and egg development, and play a role in completion and termination of non-diapause ovarian arrest in long-day macropterous females. This phenomenon was never observed in short-day brachypterous females in reproductive diapause.

Many aphidophagous coccinellids harbour male-killing bacteria. These maternally inherited bacteria kill males early in embryogenesis, female offspring of infected mothers gaining a large resource advantage from the consumption of their dead brothers. In this paper, the diversity of male-killing bacteria and their coccinellid hosts will be briefly reviewed. Thereafter, the impact that invasion by male-killers has on coccinellid hosts will be addressed in two ways. First, the selective effects due to the loss of male progeny, and the intra-genomic conflict resulting from the cytoplasmic inheritance of the bacteria will be considered. Reductions in mitochondrial diversity, effects on clutch sizes and the evolution of male-killer suppresser systems will be discussed. Second, the impact of female biased population sex ratios on the evolution of reproductive strategies and the primary sex ratio will be investigated. Preliminary results suggesting changes in male investment per copulation, reductions in female testing behaviour of males, and male biases in the progenic sex ratios of some uninfected male lines will be presented. Avenues for future work will be outlined.

The laboulbenialean fungi occur throughout the world and are closely associated with a range of arthropods, including many coleopteran hosts. Throughout the summer of 2004, coccinellids were collected from a Bluegrass savanna woodland ecosystem, dominated by blue ash Fraxinus quadrangulata and Chinkapin Oak Quercus muehlenbergii, and the adults were examined for the presence of Hesperomyces virescens using binocular and scanning electron microscopy. Over 80% of adult Harmonia axyridis, a species previously reported as having a persistent association with the fungus, were infected. No significant differences were observed in incidence on male and female hosts, however, the distribution of fungus differed between sexes. Female H. axyridis had a greater percentage of infection on their elytron compared to other parts of their body whilst male infection was concentrated around their elytra, legs and abdomen. Although infection rates were significantly lower, we report, for the first time, the presence of this fungus on the hosts Cycloneda munda, Brachiacantha quadripunctata and Psyllobora vigintimaculata. This is the first study documenting the incidence of this insect-associated fungus with these native coccinellids of North America. In the samples collected from the Bluegrass savanna, two species (Coleomegilla maculata and Hyperaspis signata) were not infected by this fungus.

In Mediterranean habitats, the specialist butterfly Euphydryas aurinia oviposits on Lonicera implexa. Previous work has shown that ovipositing females select and lay a higher number of egg clusters on certain plants. In this paper the results of a field study aimed at assessing whether females use plant size and/or plant or leaf greenness (i.e., chlorophyll concentrations) as cues for oviposition are described. Size of plants did not appear to be an important factor in determining host plant selection, probably because even small plants provide enough resources for the young larvae to reach the diapausing stage and because last instar larvae, the most likely to face resource depletion, can move great distances in search of food. Measurements of both spectral reflectance and chlorophyll concentration of plants failed to reveal differences between host and non-host plants. On the other hand, reflectance and chlorophyll concentration of leaves were found to be important in oviposition choice as egg clusters were generally located on the greenest leaves with the highest chlorophyll contents. This suggests that females use visual cues to select the leaves that will provide optimal growth opportunities for newly hatched larvae. Although there was some indication that plants receiving a greater number of egg clusters also had more leaves of high chlorophyll content, multiple egg batches on single plants could also be a consequence of females being attracted by the presence of conspecific egg clusters.

A laboratory study was carried out to determine the effects and interactions of temperature, host deprivation and adult feeding on the longevity of the parasitoid Venturia canescens (Gravenhorst) (Hymenoptera: Ichneumonidae). The effect of body size was also examined. Large wasps (hind tibia length > 1.96 mm) lived significantly longer than smaller conspecifics (hind tibia length < 1.89 mm). Adults reared at 15°C lived longer regardless of whether supplied with hosts or food. Correspondingly, adults had a shorter life at 30°C. Honey-fed adults lived significantly longer than starved adults at all temperatures and irrespective of host presence, while access to hosts resulted in a decrease in longevity at all temperatures, regardless of food supply. The Weibull distribution was used to describe the age specific survival, which in V. canescens is of "Type I", as the risk of death increases with age. Despite the significant effect of host presence on survival it was less than either temperature or feeding. The interactions between feeding, host presence and temperature proved to be significant. The objective of the study was to improve the effectiveness of V. canescens as a biological control agent of stored product pests.

Ceratophysella sigillata (Collembola, Hypogastruridae) has a life cycle which may extend for >2 years in a temperate climate. It exists in two main morphs, a winter-active morph and a summer-dormant morph in central European forests. The winter-active morph often occurs in large aggregations, wandering on leaf litter and snow surfaces and climbing on tree trunks. The summer-dormant morph is found in the upper soil layers of the forest floor. The cryobiology of the two morphs, sampled from a population near Bern in Switzerland, was examined using Differential Scanning Calorimetry to elucidate the roles of body water and the cold tolerance of individual springtails. Mean (SD) live weights were 62 ± 16 and 17 ± 6 µg for winter and summer individuals, respectively. Winter-active springtails, which were two feeding instars older than summer-dormant individuals, were significantly heavier (by up to 4 times), but contained less water (48% of fresh weight [or 0.9 g g^-1 dry weight]) compared with summer-dormant animals (70% of fresh weight [or 2.5 g g^-1 dry weight]). Summer-dormant animals had a slightly greater supercooling capacity (mean (SD) -16 ± 6°C) compared with winter-active individuals (-12 ± 3°C), and they also contained significantly larger amounts of both total body water and osmotically inactive (unfrozen) water. In the summer morph, the unfrozen fraction was 26%, compared to 11% in the winter morph. The ratio of osmotically inactive to osmotically active (freezable) water was 1 : 1.7 (summer) and 1 : 3.3 (winter); thus unfrozen water constituted 59% of the total body water during summer compared with only 30% in winter. Small, but significant, levels of thermal hysteresis were detected in the winter-active morph (0.15°C) and in summer-dormant forms (0.05°C), which would not confer protection from freezing. However, the presence of antifreeze proteins may prevent ice crystal growth when feeding on algae with associated ice crystals during winter. It is hypothesised that in summer animals a small decrease in freezable water results in a large increase in haemolymph osmolality, thereby reducing the vapour pressure gradient between the springtail and the surrounding air. A similar decrease in freezable water in winter animals will not have such a large effect. The transfer of free water into the osmotically inactive state is a possible mechanism for increasing drought survival in the summer-dormant morph. The ecophysiological differences between the summer and winter forms of C. sigillata are discussed in relation to its population ecology and survival.

The development stages of a species may have an identical lower development threshold (LDT) and proportionally different durations. This phenomenon called "rate isomorphy" (RI) has been demonstrated for a number of insect species. In contrast, the growing day degrees accumulated over the period of larval development (sum of effective temperatures SET) should be plastic and vary with environment conditions. The prediction from RI is that, with changing conditions, the uniform LDT should be accompanied by differences in development time which remain proportional at different temperatures. This was tested by investigating the effect of diet on thermal requirements for development of larvae of the polyphagous species Autographa gamma (L.) (Lepidoptera: Noctuidae). The larvae were kept at 15.0, 20.3 and 26.7°C and fed on leaves of 13dicotyledoneous herb and tree species. The proportion of total development time spent on a particular diet was plotted against temperature. The existence of RI was inferred from a zero change in development time proportion with changing temperature. This rigorous test supported RI for 3 of 9 diets where development was completed in all temperatures. The LDT observed on 11 diets where the larvae completed development in at least 2 temperatures varied between 9.3 and 11.0°C while SET varied between 167 and 353 day degrees (dd). Assuming RI, LDT and SET for those 9 diets were recalculated. The recalculated LDT was 10.0°C and SET varied between 177-257 dd. The SET increased with decreasing water content and decreasing nitrogen content of food. Worsening food quality decreased food consumption, metabolic and food conversion efficiency, and the relative growth rate of the larvae. Increasing metabolic costs of development were thus positively correlated with SET. The standardized rate of growth (mg.dd^-1) was typical for particular diets. Pupal mass decreased with increasing temperature and, within each temperature, with development length.

Wild females of Pyrrhocoris apterus exhibit seasonal changes in neuroendocrine activity and, consequently, reproduction. Long days (18 h light/6 h dark) (LD) stimulate reproduction, whereas short days (12 h light/12 h dark) (SD) induce reproductive arrest (diapause). This study reveals how photoperiod influences the expression of the circadian clock gene, period (per) in the insect's head. There is only a weak diurnal rhythm in per mRNA expression under LD and SD. However, levels of per mRNA are consistently higher (up to 10-fold) under SD than under LD. The influence of photoperiod on per gene expression is linked to a developmental output (diapause vs. reproduction); mutant females, reproducing under both LD and SD, show low per mRNA levels under both photoperiodic conditions. Thus, the magnitude of per gene expression may be important to the translation of photoperiodic signals into a hormonal message. Levels of per mRNA are related to properties of locomotor activity rhythms. Low per mRNA levels (displayed by wild females in LD and mutant females in both LD and SD) are associated with long free-running periods (τ~26-27 h) and late peaks of activity (ψR,L~10-12 h), whereas high per mRNA levels coincide with short free-running periods (τ~24 h) and early peaks of activity (ψR,L~4-6 h). Overall, the data provide a background for a molecular approach to the long-standing question about the role of the circadian system in insect photoperiodism.

Effect of photoperiod on the duration of summer and winter diapause was investigated in the cabbage butterfly, Pieris melete. By keeping naturally induced aestivating and hibernating pupae under various photoperiods, it was shown that diapause duration of aestivating pupae was significantly longer at long than at short daylengths, whereas diapause duration of hibernating pupae was significantly shorter at long than at short daylengths, suggesting both aestivating and hibernating pupae require opposite photoperiodic signals to promote diapause development. By transferring diapausing pupae, induced under various photoperiods, to 20°C with a naturally changing summer daylength, the diapause induced by short daylengths was easier to terminate than diapause induced by long daylengths. When naturally induced aestivating and hibernating pupae were kept under natural conditions, aestivating pupae had a long diapause (mean 155 days) and wide range of emergence (90 days), whereas hibernating pupae had a short diapause (mean 105 days) and a relatively synchronized emergence (lasted 30 days). Finally, the ecological significance of photoperiodic regulation of diapause duration is discussed.

We describe augmentation of managed populations of Osmia cornuta and O. rufa in the vicinity of Belgrade (Serbia). Annual augmentation of O. cornuta populations was more than five-fold during the six years of our study. This was achieved by watering the soil near the Osmia augmentation shelters used for nest building. However, populations of O. rufa under the same treatment only doubled annually. Data are also presented on sex ratios in these managed populations, the sex ratio being an important factor in increasing population numbers and raising pollination efficacy. Sex ratio values (♂ : ♀) varied from 1.46 : 1 to 3.22 : 1 in the populations of O. cornuta and from 1.35 : 1 to 2.68 : 1 in those of O. rufa.

The number of larval moults, larval head capsule width and pupal weight were investigated in both direct-developing and diapausing individuals of a South-West European population of Coenonympha pamphilus. The frequency distributions of head widths of successive larval instars overlapped, partly due to variation in the number of larval moults. The larvae that entered diapause went through five instars, instead of the four reported from this species. The evidence indicates that the five instar developmental pathway represents a plastic response rather than an example of compensatory growth. This alternative growth pattern was expressed in response to short photoperiods in parallel with, or as a consequence of, larval diapause. On average, the larvae with five instars had larger heads than their normal siblings. This resulted in comparatively heavier male pupae, while the opposite trend occurred in females. It is concluded that the variation in the number of larval instars is a plastic response to diapause when temperatures remain mild and that it might have an adaptive value in areas with mild winter climates. The sexually dimorphic expression in the larval growth patterns, in terms of pupal weight, may well imply different patterns of allocation of larval resources to adult structures, although sex-dependent differences in investment into purely larval structures cannot be discounted.

Three secondary compounds, pyrocatechol, gramine and ferulic acid from wheat were separately incorporated into artificial diets and fed to cotton bollworm Helicoverpa armigera (Hübner) larvae to determine their effects on larval and pupal weights and the nutritional indices of the larvae. The results show that these three secondary compounds can decrease the mean larval and pupal weights of cotton bollworm, with the mean larvae weights differing significantly between treatments. Mean pupal weight was only significantly reduced by ferulic acid and gramine, but not pyrocatechol. There were significant correlations between mean larval weight and concentration of the three secondary compounds tested, and between mean pupal weight and concentration of ferulic acid and gramine. The three secondary compounds tested affected the nutritional indices of cotton bollworm larvae differently. Compared with the control, ferulic acid and gramine significantly decreased RGR (the relative growth rate), AD (approximate digestibility) and ECD (conversion efficiency) of cotton bollworm larvae, and pyrocatechol only reduced ECD. All three indices were the lowest for cotton bollworm larvae fed on the diet with gramine (0.0984 ± 0.0114 g/g/day, 14.2670 ± 1.1541% and 31.1337 ± 1.1213%).

Proteinase activity in the midgut of the pentatomid stinkbug Podisus maculiventris was investigated. The optimal pH for adult and nymph proteolysis was pH 6.0 and pH 6.5, respectively. Proteinase activity was characterised using a range of diagnostic inhibitors. Activity of both adult and nymphal gut extracts, detected by the hydrolysis of Z-Phe-Arg-pNA, was inhibited to <20% of control levels by several inhibitors (e.g. E-64 and chicken egg white cystatin) associated with the inhibition of cysteine proteinases. The less specific inhibitor leupeptin reduced proteolytic activity to around 1.0% of the control values. In-gel analysis of the enzymes revealed that proteolytic activity was due to at least four proteinases, of ca. 30, 36, 50 and 110 kDa, which were all susceptible to E-64 inhibition. Salivary gland extracts gave maximal activity at pH 8.0 when tested for general proteolytic activity using fluorescent BODIPY-FL casein substrate, and showed moderate levels of inhibition when incubated with inhibitors of serine-, cysteine-, aspartic- and metallo-proteinases. Leupeptin and PMSF gave the highest levels of inhibition of salivary proteolytic activity, at ca. 50%, whilst the plant-derived inhibitors SKTI, CpTI and OC-1 did not inhibit proteolysis.

The first and third larval stages of Nearctic Anisotoma blanchardi (Horn, 1880) are described in detail and figured for the first time; measurements and chaetotaxy of head, mouthparts, thorax, abdomen, leg and urogomphi are given. Larval morphology of the blanchardi group is discussed. The blanchardi species group, proposed after a study of adult characters, is very important phylogenetically because it is a basal group in the genus and sister group to all the remaining groups. Larval characters confirm the monophyly of the group. The common larval characters of the blanchardi species group are: (i) presence of primary setae below the posterior row of terga, (ii) secondary microsculpture on the head, dense, present from the base of the head to the anterolateral arms of the epicranial suture and fronto-clypeal furrow, (iii) sclerotization around sockets of primary posterior setae of thorax of instar III, (iv) presence of clypeal furrow in the third stage, (v) presence of setae Dc1, Dd1, Dc2, Dd2a on head in instar III, (vi) urogomphomere 1 and 2 similar in length and proportion.

The first part of a revision of the European species of the genus Rhabdomastix Skuse, 1890 is presented. The history of taxonomic research on Rhabdomastix is reviewed, relationships of the genus are discussed, and the subgeneric classification outlined and re-assessed. A new subgenus, Lurdia subgen. n., is established for species centred around R. lurida (Loew, 1873), and Palaeogonomyia Meunier, 1899 and Sacandaga Alexander, 1911, previously considered subgenera, are synonymized with Rhabdomastix. A revision of the European species of Lurdia subgen. n. is presented. Two species are redescribed, Rhabdomastix (Lurdia) lurida (Loew, 1873) and R. (L.) inclinata Edwards, 1938, and the lectotype of the former is designated. Descriptions are provided of seven species, viz. R. (L.) mendli sp. n. (Switzerland, Germany, Italy), R. (L.) sublurida sp. n. (Czech Republic, Slovakia), R. (L.) furva sp. n. (Slovakia), R. (L.) loewi sp. n. (Switzerland, Germany, Austria, Italy), R. (L.) robusta sp. n. (Czech Republic, Slovakia), R. (L.) falcata sp. n. (Switzerland, Germany, Bulgaria) and R. (L.) tatrica sp. n. (Slovakia). Male and female terminalia are illustrated for all the species (except female falcata), and a key to species is appended.

Fruit of two almond, Prunus amygdalus Linnaeus, cultivars (Retsou and Truoito) containing diapausing larvae of Eurytoma amygdali Enderlein, were collected in early August from coastal areas in northern Greece. Some larvae were removed from the fruit and maintained singly in open plastic vials and others left in the fruit until the end of the low-temperature period. They were kept at a low temperature of 10°C from the beginning, or after 8 weeks at 20°C. The larvae were subsequently maintained at 20°C and whether they completed the two diapause stages was recorded for 60 more weeks. When the larvae in vials, were kept initially for 8 weeks at 20°C, most of those from Retsou and all of those Truoito almonds completed the first stage of diapause. Of the larvae in the fruits, most of those in Truoito but less than 50% of those in Retsou almonds completed the first stage of diapause after 8 weeks at 20°C. Larvae from different orchards and different almond cultivars differed in diapause intensity. When the larvae were kept at a low temperature of 10°C from the beginning for 4, 8 or 16 weeks and then at 20°C they completed the second diapause stage synchronously, but the time of completion was delayed, and depended on the duration of the low temperature treatment. In several cases the time to diapause completion was bimodally distributed and the relative size of peak depended on the duration of the early exposure to low temperature.

Geographic subspecies of several ithomiine butterflies on the lower east Andean slopes display a black and orange "melanic tiger" aposematic wing pattern that occurs from Colombia to Bolivia, while geographically adjacent lowland subspecies typically bear a coloured, "tiger" pattern. However, it is not clear whether subspecies with similar wing patterns in different regions have arisen through independent events of convergent adaptation, possibly through parapatric differentiation, or result from allopatric differentiation, as proposed by the refuge hypothesis. Here, we examine geographic patterns of divergence in the widespread and common ithomiine butterfly Hyposcada anchiala. We present phylogenetic hypotheses for 5 subspecies of H. anchiala, based on 1567 bp mitochondrial DNA. All topologies indicated that a single switch in mimetic pattern best explained the wing patterning of the H. anchiala studied here. This finding suggests that the subspecies of H. anchiala studied here result from at least two stages of differentiation, and is consistent with a single colonisation into a novel altitudinal zone coincident with a wing pattern switch, followed by subsequent divergence within, rather than across altitudinal zones. The subspecies divergences indicated diversifications were consistent with the Pleistocene. Furthermore, the lowland subspecies were more recently derived than the montane taxa, in contrast to predictions of the "Andean species pump" hypothesis.

Many gregarious insects aggregate in naturally occurring refuges on their host plants. However, when refuges are filled, they may be forced to aggregate on exposed areas of the plant. This study examines the effects of refuge saturation on group size and defence against parasitism in larvae of Ammalo helops Cramer (Lepidoptera: Arctiidae) that form day-resting groups on the trunks of weeping laurel, Ficus benjamina L., in El Salvador. Population densities, group sizes and parasitism were recorded on eight trees for each of four generations in 1995 and 1996. When population densities were low, all larvae were located in small groups in naturally occurring structural refuges (rotted out holes, spaces between crossing branches and under aerial roots) on the host plant. In contrast, when population densities were high and structural refuges were full, many larvae formed significantly larger groups (density refuges) on the open trunk. Between 20 and 24% of late-instar larvae were parasitized and this was inversely dependent on the size of within tree populations, in spite of populations being fragmented among structural refuges. Similarly, in a study carried out at a different location on young trees without structural refuges, parasitism of larvae was inversely related to group size. Although parasitism rates decreased with increasing group size, most larvae preferentially selected the small naturally occurring refuges, where groups were restricted to low densities. If this behaviour is an adaptive trait, I speculate that parasitism (or some other unmeasured mortality factor) is lower in naturally occurring refuges than in large open groups.

Paleoripiphorus deploegi gen. n., sp. n. and Macrosiagon ebboi sp. n., described from two French Albo-Cenomanian ambers (mid Cretaceous), are the oldest definitely identified representatives of the Ripiphoridae: Ripiphorinae. They belong to or are closely related to extant genera of this coleopteran subfamily. Together with Myodites burmiticus Cockerell, 1917 from the Albian Burmese amber, they demonstrate that the group is distinctly older than suggested by the hitherto available fossil record. By inference after the biology of the extant Ripiphorinae, Macrosiagon ebboi may have been parasitic on wasps and Paleoripiphorus deploegi on bees, suggesting that Apoidea may have been present in the Lower Cretaceous.

1. A study was made by knockdown sampling and branch clipping of the arthropod fauna of two native oaks (Quercus petraea and Q. robur) and of two introduced species (Q. cerris and Q. ilex) in woods near Oxford, U.K., and of two native species (Q. ilex and Q. pubescens) in southern France. Sampling was undertaken for five years in England and four years in France. All the phytophagous species except Acarina and Cecidomyidae from the Oxford samples were identified to species.
2. In England a marked seasonal pattern was observed in all years: chewing insects peaked in May, followed sequentially by sucking species, leaf miners and gall formers. The May peak on the native trees is much larger in terms of individuals, and especially in biomass, than on the introduced species. This peak is well known to provide an important food source for several species of woodland bird.
3. Most phytophages were much less abundant on the introduced oaks than on the native species. This is probably due more to the features of the leaves, than to the introduced status per se.
4. The species richness of the fauna was estimated by three methods on the basis of the total projected number of species (S_max), and its specificity to oak by reference to the known host range as recorded in the standard reference works.
5. The species richness of Heteroptera and Coleoptera on the deciduous oaks in their natural habitats (Q. petraea and Q. robur in England, Q. pubescens in France) are similar.
6. The fauna of the evergreen Q. ilex has a similar species richness both in France, where it is native, and in England, where it is introduced and where its phytophage guild is smaller than that of the deciduous species. In England the extent of oak specificity on Q. ilex is less than that of the deciduous species.
7. In England the phytophage fauna of the deciduous and introduced Q. cerris has a species richness considerably greater than that found on Q. ilex, but somewhat less than that of the deciduous and native oaks. However, the specificity of this fauna to oaks was not significantly different to that of the fauna on the native oaks.

While the ultimate causes and adaptive significance of sexual size dimorphism (SSD) have been extensively studied, the developmental mechanisms behind this phenomenon have received little attention. Going through an additional larval instar may form a specific way of achieving SSD in arthropods. In the present study, the mechanisms of SSD determination of two lymantriid moths, with marked SSD, were studied. In both species, females tended to go through an additional instar compared to males, and form pupae that were more than twice the weight of the males. To reveal the role of an extra instar, larval growth was monitored in the laboratory and the growth parameters were analysed as dependent on sex and developmental type (number of instars). Prolongation of growth by means of adding an additional larval instar in females turned out to be the key mechanism in the determination of the highly female-biased SSD in the species studied. There is thus a developmental mechanism available that permits achieving a larger size by means of extending the growth period. This provides evidence against constraint-based evolutionary explanations for body sizes in insects. There was no considerable accumulation of SSD during earlier larval life when females went through more instars than males. In contrast, in those cases in which males and females had the same number of instars, SSD accumulated gradually during the course of several larval instars. Longer growing period turned out to be a crucial mechanism leading to the female-biased SSD even when instar number did not differ between sexes, although higher instantaneous relative growth rates of females also played a complementary role in the latter case. Within sexes, an additional instar was characteristic of initially smaller larvae, as predicted by the "threshold size" hypothesis.

Haemolymph levels of amino acids, sugars and glycerol were investigated in the tenebrionid Physadesmia globosa during dehydration and rehydration. The absolute amount of amino acid decreases during dehydration and increases during rehydration, indicating active regulation of this solute (the osmolal contribution of amino acids is large - approx. 25%). Changes in the amino acid content of the haemolymph during dehydration are not the result of interchange with soluble protein; the possibility exists during rehydration (between 1 h and 48 h). Trehalose and glucose are the only sugars found in appreciable quantity in the haemolymph of this species. Their osmolal contributions (total sugar: 2.6%), and contributions to osmoregulation, are not great. Glycerol is a minor osmolar effector in the haemolymph of Physadesmia, and changes in its levels do not contribute importantly to the regulation of haemolymph osmotic pressure.

Larvae of three genera representing the staphylinid subfamily Pseudopsinae are described for the first time and illustrated with 33 morphological drawings: Pseudopsis Newman, Zalobius LeConte and Nanobius Herman. Thirty-six characters (mainly of larval morphology) were scored for representatives of six staphylinid subfamilies and a phylogenetic analysis was carried out. The monophyly of the subfamily Pseudopsinae is supported by the presence of a short oblique ridge on ventral side of larval head capsule laterad of maxillary foramina. The monophyly of each of the subfamilies Paederinae and Staphylininae is discussed based on the characters of the immature stages. The subfamily Pseudopsinae is confirmed to be a sister-group of the subfamilies Paederinae + Staphylininae on the basis of six larval synapomorphies. The latter clade is confirmed to be monophyletic on the basis of five larval synapomorphies. A larval identification key to the studied Pseudopsinae genera is provided.

Knowledge of semiochemically-mediated behavioural mechanisms of the seven-spot ladybird, Coccinella septempunctata L., is limited but sufficient to encourage further studies in the behavioural ecology of this well known insect. Recent findings on semiochemicals are discussed in relation to the main traits in the ecology of C. septempunctata. A putative autumn aggregation pheromone, and effects of allelobiotic plant interactions on habitat preferences of adults are reported. Mechanisms for interaction between an aphid alarm pheromone and plant substances are described, and the kairomonal functions of volatiles from C. septempunctata on the parasitoid Dinocampus coccinellae (Schrank) (Hymenoptera: Braconidae) are discussed. Considering the polyphagous diet of C. septempunctata, investigations on the importance of associative learning of chemical cues in foraging behaviour, and further studies on interactions with other third trophic level organisms will provide interesting lines of research.

Mass releases of Trichogramma confusum Viggiani and T. maidis Pintureau & Voegele are widely used to control lepidopterous pests. They have long been considered to be the subspecies of T. chilonis Ishii and T. brassicae Bezdenko, respectively. To re-examine the taxonomic status of these closely related Trichogramma species, the internally transcribed spacer 2 (ITS2) of ribosomal DNA was used as a molecular marker to detect between-species differences. The ITS2 regions of 7 different Trichogramma species collected from China, Germany and France were sequenced and the inter-species distances were calculated. To quantify within-species sequence variation, the ITS2 regions of 6 geographical populations of T. dendrolimi Matsumura collected from across China were sequenced and compared. The results show that the ITS2 sequences of T. confusum and T. maidis are sufficiently different from those of T. chilonis and T. brassicae, respectively, that it is difficult to group them as cryptic species, whereas there are only minor differences between the T. dendrolimi populations. The ITS2 sequences identified in this study, coupled with 67 ITS2 sequences from a wide geographical distribution retrieved from GenBank, were then used for phylogenetic analyses. The results support previous records of minor within-species ITS2 sequence divergence and distinct interspecies differences. The cladograms show the T. maidis sequence clustered within T. evanescens Westwood, while the ITS2 sequences of T. confusum and T. chilonis are clustered in different branches. Taken together, these data suggest that T. maidis is not T. brassicae, but a cryptic or sibling species of T. evanescens; T. confusum and T. chilonis are not cryptic species but two closely related sister species.