The foraging behaviors of larvae of the ladybird beetle, <Emphasis Type="Italic">Coccinella septempunctata</Emphasis> L., (Coleoptera: Coccinellidae) towards ant-tended and non-ant-tended aphids

The foraging behaviors of larvae of the ladybird, Coccinella septempunctata L., towards both the ant-tended aphid, Aphis craccivora Koch, and the non-ant-tended aphid, Acyrthosiphon pisum Harris, were investigated in the field and in laboratory experiments. Although there were no differences in the development and growth of the ladybird larvae that preyed on either Ac. pisum or Ap. craccivora, the foraging efficiency of the ladybird larvae that preyed on Ap. craccivora was higher than that of the ladybird larvae that preyed on Ac. pisum in the absence of ants. This result was explained by the fact that the number of Ac. pisum that escaped by dropping off the plant was conspicuously larger than the number of Ap. craccivora that escaped in this fashion and derived from the non-ant-attendance associated with Ac. pisum. In the laboratory experiments, fewer ladybird larvae climbed onto a plant with Ap. craccivora in the presence of ants than onto a plant with Ac. pisum in the absence of ants. The ladybird larvae did not switch from foraging for Ap. craccivora to foraging for Ac. pisum, even after suffering attacks by ants on a plant with Ap. craccivora, and it would appear that ladybird larvae are unable to remember where they have previously been attacked by ants. These results could explain why the ladybird larvae in the field more frequently visited Vicia angustifolia plants with Ap. craccivora than those with Ac. pisum and made more visits when ants were absent than when they were present.     

Expansion of the geographical distribution of an exotic ladybird beetle, Adalia bipunctata (Coleoptera: Coccinellidae), and its interspecific relationships with native ladybird beetles in Japan

The first record of the exotic ladybird beetle, Adalia bipunctata (Coleoptera; Coccinellidae), in Japan was in 1993 at Osaka Nanko Central Park. Since that time, studies on the life history and geographical distribution of A. bipunctata have been ongoing, and its establishment in the Osaka Nanko area has been confirmed. A. bipunctata is a predacious ladybird beetle and a member of a guild that overlaps in habitat and prey with that of native ladybird beetles such as Harmonia axyridis and Menochilas sexmaculatus. We investigated the distribution of A. bipunctata and its interspecific relationships with native predacious ladybird beetles. In some areas, A. bipunctata was dominant in interspecific relationships with native ladybird beetles. For the first 10 years after A. bipunctata was discovered, it occurred only in the Osaka Nanko area, but the present geographical distribution indicates that it has expanded its range. Though the population density of this species was highest at the area recorded first, and tended to decrease in inverse proportion to the distance from Osaka Nanko Central Park, a satellite occurrence was observed in a remote area. The numbers of aphid and tree species (leaf shelter for aestivation and over-wintering) utilized by A. bipunctata have recently increased. Such increases will cause the rate of distribution of A. bipunctata to accelerate. Interspecific competition between H. axyridis and A. bipunctata, which occurs earlier than H. axyridis, may be avoided by desynchronization of the occurrence seasons, and another common predacious ladybird beetle, Coccinella septempunctata, may escape interspecific competition by habitat segregation.     

Genetics and selective breeding of variation in wing truncation in a flightless aphid control agent

Augmentative biological control by predaceous ladybird beetles can be improved by using flightless morphs, which have longer residence times on the host plants. The two‐spot ladybird beetle, Adalia bipunctata (L.) (Coleoptera: Coccinellidae), is used for the biological control of aphids in greenhouses and on urban trees. Flightlessness due to truncated wings occurs at very low frequency in some natural populations of A. bipunctata. Pure‐breeding strains of this 'wingless' genotype of A. bipunctata can easily be obtained in the laboratory. Such strains have not been commercialized yet due to concerns about their reduced fitness compared to wild‐type strains, which renders mass production more expensive. Wingless strains exhibit, however, wide intra‐population phenotypic variation in the extent of wing truncation which is related to fitness traits. We here use classical quantitative genetic techniques to study the heritability and genetic architecture of variation in wing truncation in a wingless strain of A. bipunctata. Split‐families reared at one of two temperatures revealed strong family‐by‐temperature interaction: heritability was estimated as 0.64 ± 0.09 at 19 °C and 0.29 ± 0.06 at 29 °C. Artificial selection in opposite directions at 21 °C demonstrated that the degree of wing truncation can be altered within a few generations resulting in wingless phenotypes without any wing tissue (realized h² = 0.72), as well as those with minimal truncations (realized h² = 0.61) in two replicates. The latter lines produced more than twice as many individuals. This indicates that selective breeding of wing truncation may be exploited to improve mass rearing of flightless strains of A. bipunctata for commercial biological control. Our work illustrates that cryptic variation can also be a source for the selective breeding of natural enemies.     

Estimation of mortality by entomophages on exotic Harmonia axyridis versus native Adalia bipunctata in semi-field conditions in northern Italy

A semi-field experiment was carried out in two peach orchards in northern Italy to assess mortality due to predators and parasitoids on the exotic coccinellid Harmonia axyridis (Pallas) (Coleoptera: Coccinellidae) in comparison with the native coccinellid Adalia bipunctata L. (Coleoptera: Coccinellidae). The experiments were conducted in cages to avoid the possible escape of the exotic ladybird (not yet established in Italy). Two kinds of cage experiments were included: ‘exclusion cages’ (access by walking predators impeded) and ‘free cages’ (walking predators free to enter). The cages, containing all the stages of the two ladybird species, were placed in two localities and left for 24 h. All ladybird stages used for the semi-field experiments came from a laboratory rearing. The eggs of H. axyridis experienced less mortality than those of A. bipunctata. The ant workers were the most frequent predators in ‘free cages’ but A. bipunctata cannibalism on eggs was also detected. Larvae of both coccinellid species were predated equally but larval predation of L1 and L2 was higher in comparison to predation of L3 and L4. Pupae and adults of both exotic and native ladybirds were never attacked by predators. Predation on younger larval stages was higher in the ‘free cages’ in comparison with ‘exclusion cages’. No ladybird parasitisation was observed. The ‘free cage’ technique seems to provide a standardised and realistic estimation of predation impact but more studies are needed to evaluate ladybird parasitisation in semi-field conditions.     

Genetic basis and fitness consequences of winglessness in the two-spot ladybird beetle, Adalia bipunctata

The genetic basis and fitness consequences of winglessness were investigated in the two-spot ladybird beetle, Adalia bipunctata. By breeding lines from a wingless individual found at The Uithof, Utrecht in The Netherlands, the wingless condition was confirmed to be under the control of a major allele, recessive to the wild type. Wingless individuals, on average, had a longer developmental period, a lower egg production and a shorter lifespan than the wild type with wings, suggesting that the expression of the wingless allele has functionally interrelated gene actions involving a wide range of fitness components. While the wingless allele influences various traits, significant among-family variation in the degree of winglessness suggests that its phenotypic expression is also dependent on the genetic background and modifier loci. Furthermore, there was a consistent pattern of correlation between the degree of winglessness and life history traits; the most extreme wingless individuals showed the lowest fitness while those with more fully developed wings tended to have the highest fitness. This correlation suggests that the modifier genes influence both wing formation and fitness components. The significance of such epistatic effects to the evolution of flightlessness in insects is discussed.     

Sub-lethal effects of deltamethrin residues on the within-crop behaviour and distribution ofCoccinella septempunctata

The behaviour and distribution of adultCoccinella septempunctata L. (Coleoptera: Coccinellidae) were recorded in two plots of winter wheat infested with the cereal aphidsSitobion avenae (F.) andMetopolophium dirhodum (Walk.) (Homoptera: Aphididae). One plot was sprayed with the pyrethroid insecticide deltamethrin at a rate of 6.25 g a.i./ha and the other was left unsprayed. Single ladybird beetles were released sequentially on the ground at the centre of the sprayed and unsprayed plots and their behaviour and position in the crop canopy were recorded at 30 second intervals for a total of 15 min per beetle. Assessments, with fresh beetles, continued for four days after spray application with a total of eighty ladybird beetles observed. The 15 min period was selected to avoid lethal effects and no ladybird beetles were killed or knocked down as a result of exposure to deltamethrin residues during this period. Significant differences were found between the overall behaviour patterns ofC. septempunctata in the untreated and deltamethrin treated plots up to three days after the spray application. Ladybird beetles exposed to deltamethrin residues were observed to walk and groom significantly more frequently and to rest significantly less frequently than those in the unsprayed plot. Significant differences were also found between the observed distribution of ladybird beetles in the sprayed and unsprayed crop canopies, with higher numbers of observations towards the bottom of the crop canopy and on the ground in the deltamethrin treated plot than in the untreated plot during the first two days after deltamethrin application. Upon the foliage itself, ladybird beetles were observed significantly more frequently on the abaxial leaf surface in the deltamethrin treated crop compared with the untreated crop. The results are discussed in terms of possible evidence for the repellency of deltamethrin toC. septempunctata and also the implications for integrated pest management of changes in predator behaviour and crop distribution resulting from sub-lethal uptake of insecticides.     

Ladybird population dynamics in potato: comparison of native species with an invasive species, Harmonia axyridis

Following the detection of the harlequin ladybird, Harmonia axyridis, in 2003 in potato crops in Belgium, a study was carried out between 2004 and 2006 on the phenology of this species compared to native species in potato. The results confirmed the success of H. axyridis, with high population levels in 2004 and 2005. In 2006, aphid populations were very low and no H. axyridis larvae were sampled in potato, but the indigenous species Coccinella septempunctata and Propylea quatuordecimpunctata were detected. A species by species comparison of the date of first larvae detection, the larvae population peak, and the difference between this peak and the aphid population peak was performed. Results showed a clear correlation between C. septempunctata and P. quatuordecimpunctata and potato aphids, with a delay of 3.5 and 6.5 days between the aphid and ladybird population peaks for the two native species. H. axyridis arrived 7–8 days after the two indigenous species and the larval peak population occurred 15.8 days after the aphid population peak. This meant that H. axyridis had to complete its larval development with very low aphid populations or even with no aphids at all. The reason for its late arrival and the possible food resources used by H. axyridis larvae are discussed.     

Development of a wingless morph in the ladybird beetle, Adalia bipunctata

SUMMARY Many taxa of winged insects have independently lost the ability to fly and often possess reduced wings. Species exhibiting natural variation in wing morphology provide opportunities to investigate the genetics and developmental processes underlying the evolution of alternative wing morphs. Although many wing dimorphic species of beetles are known, the underlying mechanisms of variation are not well understood in this insect order. Here, we examine wing development of wild type and natural wingless morphs of the two-spot ladybird beetle, Adalia bipunctata . We show that both pairs of wings are distally truncated in the wingless adults. A laboratory population of the wingless morph displays heritable variation in the degree of wing truncation, reflecting reduced growth of the larval wing discs. The coexistence of variable wingless morphs supports the idea that typical monomorphic wingless insects may be the result of a gradual evolution of wing loss. Gene expression patterns in wing discs suggest that the conserved gene network controlling wing development in wild-type Adalia is disrupted in the dorsoventral patterning pathway in the wingless morphs. Previous research on several species of ant has revealed that the anteroposterior wing patterning pathway is disrupted in wingless workers. Future investigations should confirm whether interruptions in both taxa are limited to the patterning pathways found thus far, or whether there are also shared interruption points. Nevertheless, our results highlight that diverse mechanisms of development are likely to underlie the evolution of wingless insects.     

Interspecific interactions in a tri-trophic arthropod system: effects of a spider on the survival of larvae of three predatory ladybirds in relation to aphids

The effects of the crab spider, Misumenops tricuspidatus (Fabricius), on the larval survival of three ladybird species, Harmonia axyridis Pallas, Coccinella septempunctata L., and Propylea japonica L., in relation to aphids were investigated in the laboratory. Predation by the spider on the three ladybird species differed. All the larvae of C. septempunctata, none of H. axyridis, and an intermediate number of P. japonica were attacked and eaten by the spider. All the larvae of H. axyridis suffered mortality due to cannibalism or starvation in the treatments with and without a spider. In case of C. septempunctata, however, mortality in the early instars was significantly greater in the treatment with a spider than without a spider and no larvae developed into pupae due to predation. In the treatment without a spider, the majority of the larvae in the former treatment suffered mortality due to cannibalism or starvation, and only 13.3% of larvae developed into the adult stage. In the case of P. japonica, mortality was mainly attributed to predation in the treatment with a spider and only 26.7% became adult. In comparison, 86.7% of larvae survived to the adult stage in the treatment without a spider. In addition, in both H. axyridis and C. septempunctata, the development of young larvae was significantly slower in the presence of a spider, but this was not the case with the older larvae of H. axyridis, which indicates that the effect of the spider on larval development changed with the developmental stage of the larvae in this species. However, the spider had no significant effect on the developmental time of P. japonica larvae. Although both the spider and the ladybirds significantly affected the number of aphids, they did not have an additive effect on aphid abundance. The interactions between the spider and the ladybirds, such as intraguild predation or competition, caused them to reduce aphid population density less than the ladybirds did on their own. The effect of the spider on the larval performance of three predatory ladybirds was found to be unequal in terms of their vulnerability to predation and rate of larval development and it depended on the species and developmental stage of the ladybird.     

Negative dietary effects of Colorado potato beetle eggs for the larvae of native and introduced ladybird beetles

Aphidophagous ladybird beetles (Coleoptera: Coccinellidae) are attracted to and feed heavily on aphids, but many species will also feed opportunistically on other prey that they encounter. In potatoes (Solanum tuberosum L.) in Washington State, USA, coccinellids feed on both green peach aphids (“GPA,” Myzus persicae Sulzer) and eggs of the Colorado potato beetle (“CPB,” Leptinotarsa decemlineata Say). The guild of aphidophagous ladybirds includes two native species, Hippodamia convergens Guérin-Méneville and Coccinella transversoguttata Brown. Recently, an introduced species, Coccinella septempunctata L., has invaded and apparently displaced its native congener. A second exotic, Harmonia axyridis Pallas, has colonized the area and is becoming more abundant. We compared larval development of each species on a monotypic diet of GPA, a monotypic diet of CPB eggs, or a mixed diet of both GPA and CPB eggs. Our goal was to answer two questions: (1) do larvae of the four ladybird species benefit from including CPB eggs in their diet and (2) do the four ladybird species differ in their ability to utilize CPB eggs as prey? No larva of any species completed development on a pure diet of CPB eggs, and survivorship was highest for all species when they fed on a pure diet of GPA. One native species, H. convergens, and one exotic species, H. axyridis, exhibited significantly lower survivorship on a mixed diet of both CPB eggs and GPA, compared to a pure GPA diet; H. axyridis also took longer to develop from egg to adult when both prey were provided. Survivorship of the two Coccinella spp. was not altered by the inclusion of CPB eggs with GPA, although CPB eggs lengthened the development time of C. transversoguttata. Adult size was not consistently affected by diet for any of the coccinellids. Overall, no ladybird species benefited from the inclusion of potato beetle eggs in its diet. The two Coccinella species responded similarly to the inclusion of CPB eggs, and so we would not expect any difference in the success of coccinellid larval development in potato fields following the replacement of C. transversoguttata by C. septempunctata. Hippodamia convergens and H. axyridis, the two species whose survivorship was depressed by combining CPB egg and aphid prey, were also the two species that consumed the greatest number of CPB eggs during successful larval development. A comparison of total egg consumption by each species cohort suggested that displacement of the other species by H. axyridis would not alter CPB biological control, because the higher per capita feeding rate by H. axyridis larvae compensated for individuals’ greater mortality risk on a diet including CPB eggs.     

Current and potential management strategies against Harmonia axyridis

This paper reviews the current and potential methods to control the harlequin ladybird, Harmonia axyridis (Pallas) (Coleoptera: Coccinellidae), an Asian predatory beetle invasive in Europe and the Americas where it has become a human nuisance, a grape and wine pest and a threat to native biodiversity. Current methods to manage this invasive species include: techniques to mechanically prevent adult beetles from entering buildings in autumn or to remove aggregates of beetles inside buildings, e.g. using various trapping methods; the use of insecticides on buildings or in vineyards to prevent aggregation in houses or on grapes; cultivation practices in vineyards to lower the impact of the ladybird on grape production and wine quality; remedial treatments for wine tainted by the ladybird. Other methods are presently being developed or considered. Semiochemicals could be used as deterrents or as attractants to develop more efficient trapping systems in buildings and open fields. Natural enemies include pathogens, parasitoids, predators and a parasitic mite but few of them show potential as biological control agents. While management methods presently used or under development may eventually solve the problems caused by beetles aggregating in buildings or vineyards, the issue of H. axyridis populations outcompeting native species is much more challenging. Only the sudden adaptation of a native natural enemy or the importation of a natural enemy from the area of origin of the ladybird may ultimately lower population densities. The problems linked to the importation of an Asian natural enemy of H. axyridis are discussed.     

Invasion history, habitat preferences and phenology of the invasive ladybird Harmonia axyridis in Belgium

Harmonia axyridis Pallas (Coleoptera: Coccinellidae) is native to Asia, and was widely introduced as a biocontrol agent of aphids and coccids in Europe and North America. In Europe, H. axyridis is considered to be an invasive alien species because of its potential to disrupt native ladybird communities. Since 1999, the Belgian Ladybird Working Group mapped all Belgian Coccinellidae and recorded data on substratum plants and habitat. The first feral H. axyridis population in Belgium was recorded in 2001, but the expansion rate is decreasing because it now colonised the whole country. Recorded occupancy in Belgium showed an average rate of increase of 189% between 2002 and 2006. In Belgium, H. axyridis occurred in a wide range of habitats, including those of high conservation value. However, habitat and land cover analysis showed that H. axyridis is more frequently found in urbanised landscapes than in semi-natural landscapes. A niche overlap analysis based on plant use data showed that the potential to affect native species is higher for generalist, deciduous and coniferous tree ladybird species than for heathland and wetland specialist species. Phenology data showed that H. axyridis is able to reproduce later in the year than native species. Based on recorded distribution, ecology and phenology, we discuss the potential of H. axyridis to disrupt native ladybird assemblages in Belgium.     

A study of nonrandom mating in a British population of the two-spot ladybird with a high frequency of the melanic morph

In some studies of the two-spot ladybird (Adalia bipunctata), melanic males have been found in excess over the typical morph in matings. Data suggest that a genetic female mating preference is responsible. The mating advantage of melanic males may be important in maintaining a polymorphism between melanic and typical ladybirds in many populations in the United Kingdom (U.K.). It has been reported that preference frequency varies linearly with melanic frequency throughout most of the U.K. One particular population ofAdalia bipunctata near Aberdare, South Wales, is noted for its high frequency of melanic individuals. It has been suggested that local environmental factors account for the high melanic frequency in this population. It is also possible, however, that a female mating preference may be at least partly responsible for the high frequency of melanics (as has been proposed for the rest of the U.K.). In this study, experiments have been performed to determine the level of female mating preference in the Aberdare population. No evidence was found for any mating advantage to melanic males. There was inconsistent and unexpected evidence that melanic females were overrepresented in matings, but the cause for this was unclear. Female mating preference does not appear, therefore, to be responsible for the high melanic frequency in the population ofAdalia bipunctata near Aberdare. There is not a simple association between mating preference and melanic frequency in U. K. populations of the two-spot ladybird.     

异色瓢虫对白毛蚜捕食作用的研究

试验研究了异色瓢虫Leis axyridis(Pallas)各龄幼虫和戌虫对白毛蚜Chaitophorus po-pulialbae无翅成蚜的捕食功能反应及其成虫的寻找效应。功能反应均属Holling II型。异色瓢虫成虫寻找效应和自身密度之间的关系用Hasell & arley(1969)模型E=QP-m 和Beddington(1975)模型E=aT/［1+btm(P-1)]进行了模拟,Beddington模型更好地反映寻找效应和瓢虫密度之间的 关系。寻找效应与瓢虫成虫自身密度和蚜虫密度之间的关系用Bcddington(1995)模型E＝aT/[1+aT_mN十bt_m(P-1)]进行描述,表明寻找效应(E)随瓢虫密度(P)和猎物蚜虫密度(N)的增大而下降     

The cabbage aphid: a walking mustard oil bomb

The cabbage aphid, Brevicoryne brassicae, has developed a chemical defence system that exploits and mimics that of its host plants, involving sequestration of the major plant secondary metabolites (glucosinolates). Like its host plants, the aphid produces a myrosinase (beta-thioglucoside glucohydrolase) to catalyse the hydrolysis of glucosinolates, yielding biologically active products. Here, we demonstrate that aphid myrosinase expression in head/thoracic muscle starts during embryonic development and protein levels continue to accumulate after the nymphs are born. However, aphids are entirely dependent on the host plant for the glucosinolate substrate, which they store in the haemolymph. Uptake of a glucosinolate (sinigrin) was investigated when aphids fed on plants or an in vitro system and followed a different developmental pattern in winged and wingless aphid morphs. In nymphs of the wingless aphid morph, glucosinolate level continued to increase throughout the development to the adult stage, but the quantity in nymphs of the winged form peaked before eclosion (at day 7) and subsequently declined. Winged aphids excreted significantly higher amounts of glucosinolate in the honeydew when compared with wingless aphids, suggesting regulated transport across the gut. The higher level of sinigrin in wingless aphids had a significant negative impact on survival of a ladybird predator. Larvae of Adalia bipunctata were unable to survive when fed adult wingless aphids from a 1% sinigrin diet, but survived successfully when fed aphids from a glucosinolate-free diet (wingless or winged), or winged aphids from 1% sinigrin. The apparent lack of an effective chemical defence system in adult winged aphids possibly reflects their energetic investment in flight as an alternative predator avoidance mechanism.     

Variation in the effectiveness of abdominal shields of cassidine larvae against predators

The abdominal shields of the larvae of two tansy [Tanacetum (Chrysanthemum) vulgareL., Asteraceae] feeding species of Cassida (Coleoptera: Chrysomelidae) were tested for their ability to deter attacks by predatory insects. Cassida stigmatica Suffr. which carries an abdominal shield made of the exuviae only, and C. denticollis Suffr. which builds a compact faecal shield, were compared. Adult earwigs (Forficula auriculariaL., Dermaptera: Forficulidae), adult ladybird beetles (Coccinella septempunctata(L.), Coleoptera: Coccinellidae), and larval lacewings (Chrysoperla carnea Steph., Neuroptera: Chrysopidae) were used as predators and tested in dual choice bioassays. Against earwigs, shields of both cassidine species acted as a protective device. Earwigs preferred to feed on larvae without shields over larvae with intact shields. Adult ladybirds did not differentiate between C. stigmaticalarvae with and without exuvial shields. However, C. denticollis larvae with faecal shields were contacted at a higher frequency by ladybird beetles, even though they were less often consumed, i.e., their shield served as protection. In an olfactometer assay, faecal shields of C. denticollis were shown to have no attractive effect on the ladybird beetles. The protection for larvae with shields is likely to be caused by mechanical effects, namely the ability to move the shields. Control insects, where faecal shields of C. denticollis were glued on larvae of Galleria mellonella L. (Lepidoptera: Pyralidae), could not move their shields and were consequently consumed by the predator. Feeding by larvae of lacewings was not influenced by the presence or absence of the faecal shield. Thus, the effectiveness of the abdominal shields of tansy-feeding cassidine larvae varies with predator species, and might be based more on mechanical, than on chemical modes of action.     

The cost of being able to fly in the milkweed-oleander aphid,Aphis nerii (Homoptera: Aphididae)

Summary In the wing dimorphic milkweed-oleander aphid,Aphis nerii, winged aphids begin reproducing about 1.5 days after wingless aphids. The longer maturation period is primarily due to slower development since even adult eclosion by winged aphids takes place after wingless aphids begin reproducing. The delay is not due to a post-eclosion, pre-reproductive flight since, beginning with the fourth instar, larval winged aphids were reared at a density of one per plant and the vast majority were not stimulated to fly under such low-density conditions. Thus, the ability to fly incurs a fitness cost in terms of delayed reproduction, irrespective of whether flight actually occurs. We did not observe a difference between morphs for lifetime fecundity, even though wingless aphids have larger abdomens than winged aphids and for both morphs there is a significant correlation between abdomen width and fecundity. Offspring produced by wingless aphids over the first four days of reproduction are larger than those produced by winged aphids, and the size difference at birth is maintained into adulthood. However, there are no differences in life history traits between these offspring, including maturation period and lifetime fecundity. Thus, reduced body size does not increase the cost of being able to fly, at least under the conditions of these experiments. The cost of being able to fly in this species should favor reduced production of winged individuals in populations that exploit more permanent host plants.     

Natural flightless morphs of the ladybird beetle Adalia bipunctata improve biological control of aphids on single plants

The challenge of using ladybird beetles for biological control of insect pests such as aphids is that the adult beetles tend to fly away from the host plants. Therefore, flightless ladybirds might improve biocontrol. There are several artificial ways to obtain flightless beetles, but it may be preferable to use natural variation in flight ability. We investigated, for the first time, biocontrol by inundative augmentation of natural flightless morphs of the ladybird beetle Adalia bipunctata. Microcosm experiments using single leaves with one of three species of aphid revealed no differences in consumption behavior between flightless and winged beetles. Monitoring for 48 h of single, caged pepper plants infested with aphids of Myzus persicae nicotianae or Aulacorthum solani showed that flightless beetles had a longer residence time on the plants than winged beetles. This only translated into significantly better biocontrol of M. persicae. Despite their difference in residence time, both beetle morphs reduced the population growth of A. solani. This is probably explained by the tendency of A. solani to drop from the plant upon disturbance, and we predict that flightless beetles may outperform winged ones in the long term. Overall, our results provide a proof of principle that natural flightless A. bipunctata can improve biocontrol of aphids by ladybird beetles. However, we recognize that the effect of biocontrol will vary with the species of aphid used and that further examination in long term and large scale experiments is required.     

Queen polymorphism in the North American harvester ant,Ephebomyrmex imberbiculus

Summary In the North American harvester antEphebomyrmex imberbiculus, in addition to dealate queens, wingless female reproductives occur that have greatly reduced ocelli and thoracic sutures (intermorphic queens). Both queen types are equivalent in function, and do not differ in ovarian morphology. Colonies may contain several inseminated and egg-laying intermorphic queens. We discuss queen polymorphism in respect to the biology of this desert-dwelling species.     

Prey mediated effects of Bt maize on fitness and digestive physiology of the red spider mite predator Stethorus punctillum Weise (Coleoptera: Coccinellidae)

The present study investigated prey-mediated effects of two maize varieties expressing a truncated Cry1Ab, Compa CB (event Bt176) and DKC7565 (event MON810), on the biology of the ladybird Stethorus punctillum. Although immuno-assays demonstrated the presence of Cry1Ab in both prey and predator collected from commercial maize-growing fields, neither transgenic variety had any negative effects on survival of the predator, nor on the developmental time through to adulthood. Furthermore, no subsequent effects on ladybird fecundity were observed. As a prerequisite to studying the interaction of ladybird proteases with Cry1Ab, proteases were characterised using a range of natural and synthetic substrates with diagnostic inhibitors. These results demonstrated that this predator utilises both serine and cysteine proteases for digestion. In vitro studies demonstrated that T. urticae were not able to process or hydrolyze Cry1Ab, suggesting that the toxin passes through the prey to the third trophic level undegraded, thus presumably retaining its insecticidal properties. In contrast, S. punctillum was able to activate the 130 kDa protoxin into the 65 kDa fragment; a fragment of similar size was also obtained with bovine trypsin, which is known to cleave the protoxin to the active form. Thus, despite a potential hazard to the ladybird of Bt-expressing maize (since the predator was both exposed to, and able to proteolytically cleave the toxin, at least in vitro), no deleterious effects were observed.