Astylus atromaculatus (Coleoptera: Melyridae): abundance and role in pollen dispersal in Bt and non-Bt cotton in South Africa

In South Africa, modified Bt (Cry1 Ac) cotton cultivars and organic ones coexist. This raises the question of the risk of dissemination of genetically modified (GM) pollen to non-GM crops by visiting insects. We inventoried the flower-visiting insects in Bt and non-Bt cotton fields of the South African Highveld region and investigated their role in pollen dispersal. Their diversity and abundance varied slightly among sites, with Astylus atromaculatus as the predominant insect on both Bt and non-Bt cotton flowers. The other major flower-visiting species were Apis mellifera and solitary Apidae. No differences were found in the abundance of each taxum between Bt and non-Bt cotton except for Scoliidae and Nitidulidae, which were scarce overall (<0.5%) but more abundant on the non-Bt flowers in the central area of the field at one site. The pollen load on A. atromaculatus was as high as on Apis mellifera. Cage tests showed that A. atromaculatus can pollinate female cotton plants by transferring pollen from male donor plants. In the field, the flight range of this insect was generally short (25 m), but it can occasionally reach up to 200 m or even more. This study therefore highlights that A. atromaculatus, commonly regarded as a pest, could be an unexpected but efficient pollinator. Because its population density can be high, this species could mediate unwanted cotton pollen flow when distances between coexiting fields are not sufficient.     

Visual and olfactory cues for mate orientation behaviour in male white-spotted longicorn beetle, Anoplophora malasiaca

Olfactory and visual cues were shown to mediate short‐distance orientation in Anoplophora malasiaca (Thomson) (Coleoptera: Cerambycidae). In a laboratory test, more than 80% (n = 42) of males walked straight upward when presented with an untreated surface with a 75° slope. When a freshly killed female was fixed at a short distance (10 cm ahead and 5 cm to left/right) from the starting point, 50% of males (n = 30) were oriented toward the female before direct contact. Similar behavioural responses were observed when female extract was directly applied to the slope or to a glass rod model fixed on the slope. When black, white, and transparent coloured rods with the extract were presented, the orientation response was significantly greater for black than to white and transparent rods, to which only a negligible response was observed.     

无翅桃蚜对龟纹瓢虫的视觉和嗅觉识别反应

为探明桃蚜Myzus persicae是否可以识别来自其捕食性天敌的嗅觉和视觉信息,本研究采用桃蚜和龟纹瓢虫Propylaea japonica这一猎物-捕食者系统,在室内测定了无翅桃蚜对龟纹瓢虫成虫体色和挥发物的识别反应。选择反应试验结果表明,无翅桃蚜既能通过视觉信息识别瓢虫的存在,也能通过嗅觉信息识别瓢虫的存在,说明桃蚜对龟纹瓢虫体色和气味信息的识别存在一定的冗余现象。剂量反应试验结果表明,龟纹瓢虫粗提物的剂量与其对桃蚜的驱避率呈现良好的线性关系,识别反应剂量的临界值在0.3~0.6个瓢虫当量之间,1.2~1.5个瓢虫当量的粗提物的驱避作用与20头活体龟纹瓢虫的驱避作用相当。结论认为,桃蚜可以识别龟纹瓢虫的存在,并对其作出一定的躲避反应,从而降低被捕食的风险。     

Interactions between the predators thanasimus formicarius (Col.: Cleridae) and rhizophagus depressus (Col: Rhizophagidae), and the bark beetle tomicus Piniperda (Col.: Scolytidae)

The occurrences of Thanasimus formicarius (L.) (Cleridae), Rhizophagus depressus (F.) (Rhizophagidae), and Epuraea marseuli Reitter (Nitidulidae) in cut Scots pines, Pinus sylvestris L., attacked by Tomicus piniperda (L.) (Col.: Scolytidae) were recorded in the field, and interactions between the species were studied in caged pine bolts attacked by T. piniperda. T. formicarius eggs and R. depressus adults were abundant in the T. piniperda attacked trees, whereas only a few individuals of E. marseuli were found. T. formicarius and R. depressus, but not E. marseuli, reproduced in the caged bolts. T. piniperda offspring production per unit area of bark was reduced by 41% when reared with R. depressus, by 81% when reared with T. formicarius, and by 89% when all three species were reared together, compared with T. piniperda alone. The interaction between T. formicarius and R. depressus was mutually antagonistic. When both species were present in the same bolt the total number of larvae was reduced by 49% for R. depressus and the number of large larvae (length > 10 mm) was reduced by 35% for T. formicarius compared with their respective production values when each species was present alone with the bark beetle. There was a positive relationship between T. piniperda egg gallery density and the production of R. depressus larvae per m². Larvae of both R. depressus and T. formicarius developed into new adults during the first summer.

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Résumé Interactions entre les prédateursThanasimus formicarius (Col.: Cleridae) etRhizophagus depressus (Col.: Rhizophagidae) et le scolyteTomicus piniperda (Col.: Scolytidae) La présence deThanasimus formicarius (L.) (Cleridae),Rhizophagus depressus (F.) (Rhizophagidae), etEpuraea marseuli Reitter (Nitidulidae) a été étudiée sur le terrain dans des pins sylvestres (Pinus sylvestiris L) abattus, attaqués partomicus piniperda (L.) (Col.: Scolytidae) et les relations entre les espèces ont été étudiées sur des rondins de pin attaqués parT. piniperda et placés sous cage. Le nombre d’∄ufs deT. formicarius et d’adultes deR. depressus était important dans les arbres attaqués parT. piniperda, alors que seuls quelques individus deE. marseuli ont pu être trouvés.T. formicarius etR. depressus, mais pasE. marseuli, se sont reproduits dans les rondins sous cage. La production de descendants deT. piniperda par unité de surface d’écorce était réduite de 41% quand le scolyte était élevé avecR. depressus, de 81% en élevage avecT. formicarius et de 89% quand les trois espèces sont élevées ensemble, par comparaison avecT. piniperda seul. Les interactions entreT. formicarius etR. depressus étaient mutuellement antagonistes. Quand les deux espèces étaient présentes dans le même rondin, le nombre total de larves était réduit de 49% pourR. depressus et le nombre de grosses larves (longueur > 10 mm) était réduit de 35% pourT. formicarius comparé aux valeurs respectives quand chaque espèce était présente isolément avec le scolyte. Il y a une corrélation positive entre la densité de galeries avec des ∄ufs deT. piniperda et la production de larves deR. depressus par m². Les larves deR. depressus et deT. formicarius se sont transformés en adultes l’été suivant.

     

The importance of olfactory and visual cues in developing better monitoring tools for Sirex noctilio (Hymenoptera: Siricidae)

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Responses to olfactory and visual cues by over-wintered and summer generations of the pollen beetle, Meligethes aeneus

Abstract.  Behavioural responses to odours of oilseed rape in bud and flower stage and to green and yellow colours are studied for the two main phenological stages of pollen beetles, Meligethes aeneus , a major pest of oilseed rape, Brassica napus . Over-wintered individuals oviposit in buds of oilseed rape. Adults of the new generation (i.e. the summer generation) feed on flowers of different plant species before over wintering. In olfactometer experiments, the over-wintered beetles display a higher preference for odour of oilseed rape at the bud stage compared with the summer generation, both with and without colour stimuli. Flower odours are preferred in combination with yellow colour. Colour stimuli presented alone do not affect the behaviour. The summer generation beetles respond to both bud and flower odour. Adding colour stimuli changes the summer generations preference towards yellow and flower odour.     

Close-range, in-flight integration of olfactory and visual information by a host-seeking bark beetle

A long‐standing controversy questions whether foraging bark beetles assess the suitability of individual host trees using cues at close range while flying or engage in random landing followed by contact assessment. In most cases, visual discrimination mechanisms are ignored. We show that pheromone‐responding mountain pine beetles (MPB), Dendroctonus ponderosae Hopkins (Coleoptera: Scolytidae), can visually discriminate between ‘host’ (black) and ‘non‐host’ (white) traps arranged in small clusters, in the absence of additional host olfactory information, and that males (but not females) demonstrate a greater preference for combined host visual and olfactory cues. However, white, non‐host traps baited with a host volatile were as attractive as unbaited, black host traps. Our results support the hypotheses that when deciding to land, the MPBs integrate visual and olfactory information and can process cues in both sensory modes at relatively close range (≤2 m). Thus, host selection mechanisms in this species are unlikely to be random with respect to either sensory mode.     

两种诱集方式对田间金龟甲诱集效果的比较研究

为了明确灯诱和引诱剂对田间金龟害虫的诱捕效果,利用自动虫情测报灯和2种引诱剂诱捕器对同一块花生田发生的金龟甲的诱集效果进行了对比试验。结果表明,两种方式对金龟甲的诱集效果差异明显。诱虫灯对东北大黑鳃金龟Holotrichia diomphalia和铜绿丽金龟Anomala corpulenta的日均诱虫量分别为3.30头和1.27头,引诱剂诱捕器对两种金龟甲的日均诱虫量分别为1.25头和0.34头。自动虫情测报灯的诱虫总量和持效性较好,均明显优于引诱剂诱捕器的诱捕效果。引诱剂诱捕器对雌性东北大黑鳃金龟的特异诱集效果优于自动虫情测报灯。尽管两种诱捕方式全年诱虫量存在较大差异,但两者所监测得到的金龟甲发生动态趋势基本一致,且特殊气象条件诱集数据可相互补充,并提出大面积防治工作中应以虫情测报灯为主,引诱剂诱捕器可作为重要辅助手段。     

Pollinator attraction in Cornus capitata (Cornaceae): the relative role of visual and olfactory cues

Aims It is generally accepted that visual displays and floral scent play important roles in communication between flowering plants and their pollinators. However, the relative role of visual and olfactory cues in pollinator attraction is largely unknown. In this study, we determined the roles of both types of cue in attracting pollinators to Cornus capitata, a medium sized tree with each capitulum surrounded by four large, white, petaloid bracts.Methods Pollinator observations and pollination experiments were conducted in a natural population; the inflorescences' visual and olfactory signals were characterized by spectral and chemical analyses; the responses of pollinators to visual and olfactory cues were tested using dual-choice behavioural bioassays; the relative roles of visual and olfactory cues in pollinator attraction were tested by comparing the responses of pollinators to inflorescences subjected to three experimental treatments (intact, all bracts removed, and capitulum removed) within the natural population.Important findings For fruit set, C. capitata is entirely dependent on pollinators, with a bee, Anthophora sp., being the main pollinator. Bracts present high colour distance and green contrast against the leaves. Twelve volatile compounds in the floral scent were detected, most of which have previously been reported to be attractive to a broad spectrum of bee species. Behavioural bioassays showed that both, visual cues alone and olfactory cues alone, are attractive to pollinating bees. However, visual cues alone attracted significantly more approaches than olfactory cues alone, while olfactory cues alone elicited a significantly higher landing percentage than visual cues alone. The finding suggests that, in the C. capitata – Anthophora sp. interaction, visual cues are mainly used for location from long distances, while olfactory cues mainly aid landing from short distances. Our results indicate that different modalities of floral cues should be considered together to understand fully the communication between flowering plant and pollinators.     

Laboratory and greenhouse evaluation of a synthetic host volatile attractant for Colorado potato beetle, Leptinotarsa decemlineata (Say)

Abstract 1 The attractiveness of potato plants treated with a synthetic host volatile blend [(Z)‐3‐hexenyl acetate (+/–)‐linalool, and methyl salicylate] to newly emerged and 5‐day‐old adult Colorado potato beetle, Leptinotarsa decemlineata (Say), was compared at four doses against untreated control plants and plants treated with an azadirachtin‐based antifeedant in greenhouse cage arenas. 2 Attractant‐treated plants (derived release rates of 0, 5.7, 17.1 or 57 µg/h) were significantly more attractive than untreated control plants to newly emerged and 5‐day‐old adults only at 57 µg/h. 3 Attractant‐treated plants were significantly more attractive than antifeedant‐treated plants to newly emerged and 5‐day‐old adults at the 5.7 µg/h treatment level and higher. Mean insect density on attractant‐treated plants in the attractant/antifeedant study was significantly higher than in the attractant/control study. 4 Habituation to the synthetic attractant was evaluated by exposing adult beetles to the synthetic attractant for 0, 1, 2.5, 4, 8, 12 or 16 h, before release into a wind tunnel in which an attractant‐baited plant model was placed at the upwind end. Insects exposed to the synthetic host attractant for ≤ 8 h moved to the synthetic attractant‐baited plant model whereas insects exposed to the synthetic host attractant for 12 and 16 h did not. Furthermore, beetles exposed to the synthetic attractant for 0 and 1 h moved at rates greater than, or equal to, the median whereas beetles exposed for longer time periods moved at rates significantly less than the median. 5 These results demonstrate the potential for using the synthetic plant attractant and an antifeedant as components in a stimulo‐deterrent strategy for management of the Colorado potato beetle as shown by us in another study.     

Cytogenetic analysis of Astylus antis (Perty, 1830) (Coleoptera, Melyridae): Karyotype, heterochromatin and location of ribosomal genes

Cytogenetic analysis of Astylus antis using mitotic and meiotic cells was performed to characterize the haploid and diploid numbers, sex determination system, chromosome morphology, constitutive heterochromatin distribution pattern and chromosomes carrying nucleolus organizer regions (NORs). Analysis of spermatogonial metaphase cells revealed the diploid number 2n = 18, with mostly metacentric chromosomes. Metaphase I cells exhibited 2n = 8II+Xyp and a parachute configuration of the sex chromosomes. Spermatogonial metaphase cells submitted to C-banding showed the presence of small dots of constitutive heterochromatin in the centromeric regions of nearly all the autosomes and on the short arm of the X chromosome (Xp), as well as an additional band on one of the arms of pair 1. Mitotic cells submitted to double staining with base-specific fluorochromes (DAPI-CMA(3) ) revealed no regions rich in A+T or G+C sequences. Analysis of spermatogonial mitotic cells after sequential Giemsa/AgNO (3) staining did not reveal any specific mark on the chromosomes. Meiotic metaphase I cells stained with silver nitrate revealed a strong impregnation associated to the sex chromosomes, and in situ hybridization with an 18S rDNA probe showed ribosomal cistrons in an autosomal bivalent.     

Prolonged development time of the bark beetle predator Thanasimus formicarius (Col.: Cleridae) in relation to its prey species Tomicus piniperda (L.) and Ips typographus (L.) (Col.: Scolytidae)

1 The generation time of the bark beetle predator Thanasimus formicarius (L.) (Col.: Cleridae) was found to be predominantly two years both in the field and in rearing experiments conducted with two of its main prey species, the pine shoot beetle Tomicus piniperda (L.) and the spruce bark beetle Ips typographus (L.) (Col.: Scolytidae). 2 Emergence of T. formicarius adults in the first summer was only observed in one of the two rearing experiments, and these individuals represented only 6% of that generation. 3 All individuals not emerging as adults in the first summer remained as larvae in their pupal chambers until the second summer. Pupae were found starting around mid-June, and adults (in pupal chambers) were found from late July through to the end of August. 4 Newly emerged adults had to feed in order to survive hibernation. 5 The existence of T. formicarius races, specialized on certain bark beetle species and with phenologies matching their hosts, could not be demonstrated. After hibernation there was no difference in feeding activity, timing of egg-laying or proportion of egg-laying females between the T. formicarius adults reared as larvae on T. piniperda (flight period in April) and those reared as larvae on I. typographus (main flight period generally starting in late May or early June) when exposed to a temperature and day-length typical of the early spring conditions prevailing during the flight period of T. piniperda. 6 T. formicarius was parasitized by Enclisis vindex (Tschek) (Hym.: Ichneumonidae) in the pupal chamber. 7 The importance of these findings for the population dynamics of bark beetles is discussed.     

Integration of visual and olfactory cues of hosts and non-hosts by three bark beetles (Coleoptera: Scolytidae)

Abstract.  1. There has been a long-standing pre-occupation with how phytophagous insects use olfactory cues to discriminate hosts from non-hosts. Foragers, however, should use whatever cues are accurate and easily assessed, including visual cues.
2. It was hypothesised that three bark beetles, the mountain pine beetle (MPB), Dendroctonus ponderosae Hopkins, the Douglas-fir beetle (DFB), D. pseudotsugae Hopkins, and the western balsam bark beetle (WBBB), Dryocoetes confusus Swaine, integrate visual and olfactory information to avoid non-host angiosperms (e.g. paper birch, trembling aspen), that differ in visual and semiochemical profile from their respective host conifers (lodgepole pine, Douglas-fir, interior fir), and tested this hypothesis in a series of field trapping experiments.
3. All three species avoided attractant-baited, white (non-host simulating) multiple-funnel traps, and preferred attractant-baited black (host-simulating) traps. In experiments combining white, non-host traps with non-host angiosperm volatiles, bark beetles were repelled by these stimuli in an additive or redundant manner, confirming that these species could integrate visual and olfactory information to avoid non-host angiosperms while flying.
4. When antiaggregation pheromones were released from white traps, the DFB and MPB were repelled in an additive-redundant manner, suggesting that beetles can integrate diverse and potentially anomalous stimuli.
5. The MPB demonstrated the most consistent visual preferences, suggesting that it may be more of a 'visual specialist' than the DFB or WBBB, for which visual responses may be more contingent on olfactory inputs.     

Food preferences and the value of animal food for the carabid beetle Amara similata (Gyll.) (Col., Carabidae)

Abstract:  Several studies have shown that the mainly granivorous carabid beetles, e.g. Amara spp., include animal food in their diet to a considerable extent. We therefore hypothesized that the performance of these beetles would be enhanced by dietary mixing including both seeds and animal food. In order to test this, we conducted laboratory feeding experiments with adults and larvae of Amara similata . Both adults and larvae were subjected to different diet treatments including: seeds, houseflies, grasshoppers, earthworms, slugs and snails in pure and mixed diets. Larval survival, development time, pupal and teneral weights were used as indicators of food quality for the larvae. For the adult beetles, mass change was used as an indicator of food quality. We found seeds to be high-quality food, while all pure animal diets were of low quality for both adults and larvae. Animal foods added to the seed diet had both positive and negative effects. A mixed diet of all foods enhanced the mass gain of adults compared with the seed diet, but reduced larval performance dramatically. Earthworms and grasshoppers added to seeds increased the pupal and teneral weights, while reduced larval survival. Thus, A. similata is omnivorous with a mainly granivorous feeding habit. It may gain benefits on some fitness parameters and incur costs on others from preying or scavenging on animal food. Therefore, the overall fitness consequences of a mixed seed-animal diet are uncertain.     

Role of visual and olfactory cues from agricultural hedgerows in the orientation behavior of multicolored Asian lady beetle (Coleoptera: Coccinellidae)

Harmonia axyridis Pallas is an introduced lady beetle common in eastern North American agroecosystems. Two-choice behavioral bioassays were performed to determine whether visual and olfactory stimuli from prey and host habitats could elicit taxis in wild-collected H. axyridis adults and whether beetles exhibit a preference among stimuli. Soybean aphid (Aphis glycines Matsumura) spends much of the year in agricultural hedgerows residing on buckthorn (Rhamnus cathartica L), and H. axyridis is frequently observed feeding on aphids in this habitat. Olfactory bioassays were performed in a Y-tube olfactometer and tested the response of beetles to the odor of buckthorn leaves, apple leaves (Malus domestica Borkh.), and buckthorn leaves both naturally and artificially infested with A. glycines. No differences were observed between the numbers of beetles moving toward the odor of buckthorn artificially infested with A. glycines and uninfested buckthorn, but more beetles preferred naturally infested buckthorn over uninfested buckthorn. Visual bioassays were performed in an acrylic tube arena,and tested beetle response to silhouettes and to apple and buckhorn leaves. Beetles were significantly more likely to choose silhouettes over blank space in visual trials. Significantly more beetles moved toward buckthorn leaves than blank space, but beetles did not discern between apple and buckthorn until olfactory cues were also included. This study lays the foundation for future work examining the response of H. axyridis to visual and olfactory cues in Ontario agroecosystems, which could help enhance effectiveness of H. axyridis as a biological control and mitigate its impacts as a pest species.     

Establishment of the Amplified Fragment Length Polymorphism (AFLP) technique for genotyping of pollen beetle (Meligethes aeneus) - a noxious insect pest on oilseed rape (Brassica napus)

In order to conduct studies concerning genetic variability of pollen beetles (Meligethes aeneus), a genotyping protocol was established. No genome information is available for pollen beetles so the amplified fragment length polymorphism (AFLP) technique was chosen since it does not depend on any prior sequence information of the samples and also is a sensitive and robust technique. However, several modifications were needed in order to adapt the method for analysis of pollen beetles. Basic modifications included (i) alterations of DNA purification, (ii) use of two six-cutter restriction enzymes, (iii) and modified PCR conditions. This protocol resulted in a favourable number of fragments of an appropriate size range for standard gel analysis by a DNA sequencer applicable to a single insect and even body parts enabling different assays to be conducted on a single specimen. Pollen beetles from different areas of Sweden were analysed to verify the reproducibility and efficacy of the protocol as well as for phenetic analysis. The high reproducibility of the modified AFLP protocol allows it to be used as a reliable tool for genotype analysis of pollen beetles.     

Evaluating a predator–prey interaction in the field: the interaction between beetle larvae (predator) and tadpoles (prey)

The larval amphibian community of temporary pond ecosystems has served as a model for studies in community ecology, with a majority of this work being conducted in mesocosms. Recent research has suggested that mesocosms may overestimate ecological effects; therefore, experimental studies conducted under field conditions are required to gauge the results of mesocosm studies. To assess a species interaction under more natural conditions, we conducted a series of field experiments examining the predator–prey interaction between beetle larvae ( Dytiscus sp.; predator) and larval wood frogs Rana sylvatica (prey) in central Pennsylvania, USA. Quantitative sampling of woodland ponds indicated that beetle larvae of the genus Dytiscus were the most common predator of tadpoles. In a field enclosure experiment, dytiscids were effective predators of tadpoles in the pond environment. Moreover, tadpoles avoided areas in a pond containing caged dytiscids, demonstrating that tadpoles recognize the chemical stimuli of predators in complex environments. The results of this study are consistent with data from prior laboratory and mesocosm studies and suggest that these venues can produce reliable interpretations of predator–prey dynamics in this community.