Mating behaviour of female Tuta absoluta (Lepidoptera: Gelechiidae): polyandry increases reproductive output

Tuta absoluta (Meyrick) is an important pest of tomato. Mass trapping of males has seldom proved an effective control measure, probably due to the pest’s reproductive biology. There are few studies on female mating behaviour. For this reason, this study aimed to determine female mating frequency and its effects on reproductive output and female longevity; the effects of male mating status on female reproductive output and longevity and the fate of the spermatophore inside the bursa copulatrix. The studied population of T. absoluta mated only once a day at the beginning of the photophase, females remated frequently and can be classified as polyandrous. The refractory period of both T. absoluta males and females was very short and was not observed in many cases. The lack of refractory period could be due to the female’s rapid metabolism of the spermatophore thus allowing the female to reduce the intermating interval and mate again. Remating had direct benefits for T. absoluta females increasing their fecundity, fertility and longevity. These benefits were greater when females could remate to virgin males instead of to the same male. In this species, therefore, polyandry has direct benefits for the female. The occurrence of polyandry together with other known or unknown reasons can explain the failure of control methods based on pheromones in the open greenhouses in some tomato-growing areas.     

Effects of X-rays on Tuta absoluta for use in inherited sterility programmes

Tuta absoluta is a key pest of tomato crops originating from South America. The consequences of X-radiation on this species were studied under laboratory controlled conditions. The effect of radiation on adult emergence was evaluated exposing male and female pupae to increasing X-rays. Adult emergence decreased as doses of X-radiation increased, with the appearance of deformities such as malformed wings and bent legs at doses ≥350?Gy. Besides, males and females obtained from irradiated pupae were out crossed with untreated counterparts to explore the effects of X-radiation on inherited sterility. (a) Irradiated male?×?untreated female crosses. Both fecundity and fertility of the untreated females were reduced by radiation, and the effect was stronger as the doses increased. Neither the longevity of parental males and F1 adults nor the sex ratios of the F1 and F2 generations were affected by X-radiation (F1 and F2: first and second generation of descendants of irradiated adults). Inherited sterility effects were manifested by a significant reduction in the F1 fecundity, F1 fertility, and the amount of larvae and pupae produced. Doses of 200–250?Gy could be used to induce inherited sterility in T. absoluta males. (b) Untreated male?×?irradiated female crosses. The minimum dose at which irradiated females were completely sterile was 200?Gy. The present study is the first study in T. absoluta that provides the starting point for implementing the inherited sterility in this species.     

Biological invasion of European tomato crops by Tuta absoluta: ecology, geographic expansion and prospects for biological control

The tomato leafminer Tuta absoluta (Meyrick) (Lepidoptera: Gelechiidae) is a devastating pest of tomato originating from South America. After its initial detection in eastern Spain in 2006, it rapidly invaded various other European countries and spread throughout the Mediterranean basin. If no control measures are taken, then the pest can cause up to 80–100% yield losses in tomato crops in recently invaded areas and may pose a threat to both greenhouse and open-field tomato production. The exceptional speed and extent of T. absoluta invasion have called for studies documenting its biology and ecology, while indicating an urgent need for efficient and sustainable management methods. The development of approaches to manage T. absoluta would be facilitated through a detailed revision of information on this pest in its area of origin. This review combines information on the invasion by T. absoluta, its ecology, and potential management strategies, including data that may help the implementation of efficient biological control programs. These programs, together with a variety of other management tactics, may allow efficient integrated pest management of T. absoluta in Europe and Mediterranean Basin countries.     

Pre-exposure to sex pheromone did not affect mating behavior in the sweetpotato weevil <Emphasis Type="Italic">Cylas formicarius</Emphasis>

In sterile insect technique (SIT) programs, the released sterile males are important for their effectiveness. The use of sex pheromones to collect males is economical; however, pre-exposure to sex pheromones may affect male mating behavior, and would thus reduce the effectiveness of the SIT programs. Males exposed to sex pheromone may become attractive to other males due to pheromone adsorption on their body impregnation, prevent mating and reduce the dispersal of sterile males. We examined the effect of pre-exposure to sex pheromone on the mating behavior of male sweetpotato weevil Cylas formicarius. Pre-exposure to high-dose sex pheromone for 24 h did not affect the male mating behavior of C. formicarius, and the exposed males did not attract other males. These results suggest that male C. formicarius that were collected from a mass-rearing facility using sex pheromone can be effectively used in SIT programs.     

Side effects of selected insecticides on the <Emphasis Type="Italic">Tuta absoluta</Emphasis> (Lepidoptera: Gelechiidae) predators <Emphasis Type="Italic">Macrolophus pygmaeus</Emphasis> and <Emphasis Type="Italic">Nesidiocoris tenuis</Emphasis> (Hemiptera: Miridae)

Tuta absoluta is a pest native to South America that produces significant damage to tomato crops and was first detected in Europe in late 2006. Data obtained during 2008 from commercial tomato crops in which IPM was applied suggested that good pest control was possible through the combined action of the predatory mirid bugs Macrolophus pygmaeus and Nesidiocoris tenuis and the use of selective insecticides. The aim of our study was to evaluate the lethal and sublethal side effects of three of the insecticides most widely used to control T. absoluta on these predators: azadirachtin, spinosad and indoxacarb. Seven days after applying the treatment at the maximum recommended field rates, the mortality produced by indoxacarb ranged from 28% for nymphs of M. pygmaeus to 77% for females of N. tenuis and were significantly higher than those produced by azadirachtin, spinosad and the control (<13%). However, indoxacarb did not affect the number of descendants of females exposed to residues during the last days of their preimaginal development. In contrast, spinosad significantly reduced the offspring of M. pygmaeus and azadirachtin significantly reduced the offspring of N. tenuis females. The sublethal effects of azadirachtin and spinosad on predator reproduction should therefore not be ignored. This information could be useful when selecting the most appropriate insecticide to control T. absoluta in greenhouses and field crops in which M. pygmaeus and N. tenuis are used as biological control agents.     

Sexual communication and related behaviours in Tephritidae: current knowledge and potential applications for Integrated Pest Management

Tephritidae are an enormous threat to fruit and vegetable production throughout the world, causing both quantitative and qualitative losses. Investigating mating sequences could help to unravel mate choice dynamics, adding useful information to improve behaviour-based control strategies. We review current knowledge about sexual communication and related behaviours in Tephritidae, with a focus on six key agricultural pests: Anastrepha ludens, Bactrocera cucurbitae, Bactrocera dorsalis, Bactrocera oleae, Ceratitis capitata and Rhagoletis pomonella. We examine features and the role of male–male combat in lekking sites, cues affecting mating dynamics, and some fitness-promoting female behaviours that occur at oviposition sites [the use of oviposition marking pheromones (OMPs) and female–female fights for single oviposition sites]. We outline future perspectives and potential contributions of knowledge about sexual communication to Integrated Pest Management programs for tephritid pests. Sexually selected traits are frequently good indicators of male fitness and knowledge of sexual selection processes may contribute to the improvement of the sterile insect technique (SIT), to select genotypes with high reproductive success and to promote sexually selected phenotypes through mass-rearing optimization. Furthermore, males’ exposure to parapheromones, such as phenyl propanoids (PPs), ginger root oil and trimedlure can enhance the mating success of sterile flies used in SIT programs. PPs are also a powerful tool to improve reduced-risk monitoring dispensers and the male annihilation technique, with low side effects on non-target insects. Lastly, we outline the possibility to sensitise or train mass-reared parasitoids on OMPs during the pre-release phase, in order to improve their post-release performance in the field.     

Does indirect mating trophallaxis boost male mating success and female egg load in Mediterranean fruit flies?

Mating trophallaxis represents a fascinating strategy adopted by males of several animal species to affect the decision-making of females during mating. Among tephritids, few species perform mating trophallaxis. However, this phenomenon has been little studied in major tephritid pests. We reported the presence of indirect mating trophallaxis in Mediterranean fruit flies, Ceratitis capitata, showing its influence on the main mating traits, male mating success and female egg load. Of 219 mating pairs, only 27 of them showed mating trophallaxis, indicating that mating trophallaxis may represent a significant male energy investment. The duration of male wing vibration and the whole precopula phase was longer in pairs that mated without trophallaxis compared to the pairs displaying mating trophallaxis. Males that displayed trophallaxis performed a longer whole duration of the courtship and mating sequence, with no differences in copula duration. Male mating success was slightly increased by trophallaxis. The majority of males performing trophallaxis skipped wing vibration during courtship, while all males courting females without trophallaxis relied on wing vibration to attract females within short distances. No egg load differences were reported for females that consumed nuptial gifts over control females. Overall, our research sheds light on the relation between indirect mating trophallaxis and egg load production in medflies, providing a better understanding of sexual selective mechanisms as the basis of courtship and mating behaviour in tephritid flies. Furthermore, this behaviour could be used as a quality control parameter to assess medfly mass-reared strains, in order to improve sterile insect technique programmes.     

天牛类昆虫交配行为研究进展

天牛是一类在我国危害严重且防治难度较大的林木蛀干害虫.虽然其种类众多,经济和生态价值大,但国内外较少有对天牛繁殖交配行为的总结报道.梳理国内外对天牛交配行为的研究,发现天牛交配行为可分为求偶、性冲动、交配前准备、交配四个阶段,每个阶段都不可缺少,且有其阶段特征性的行为.在交配后,一些雄性天牛会表现出配后保护行为.天牛交...     

Biology of two key Palaearctic larval ectoparasitoids when parasitizing the invasive pest Tuta absoluta

During the last few years following the invasion of European tomato crops by the invasive South American tomato leafminer, Tuta absoluta (Meyrick) (Lepidoptera: Gelechiidae), several indigenous larval parasitoid species were recorded as natural enemies of this pest. Necremnus cf. artynes (Walker) and to a lesser extent Stenomesius sp. nr. japonicus (Ashmead) (Hymenoptera: Eulophidae) have been frequently reported attacking T. absoluta in tomato greenhouses in Europe and they are considered as possible biocontrol agents. Few biological data are available on these two species, notably when they parasitize T. absoluta. Therefore, the present study documents their biology when parasitizing T. absoluta, and provides scientific bases for potential development of biological control programs relying on larval ectoparasitoids in invaded areas. We demonstrated the ability of the two parasitoid species to reproduce on T. absoluta as host on tomato plants. On average, N. cf. artynes female parasitized 28.5 larvae and killed 26.2 larvae during its life time whereas S. sp. nr. japonicus female was more long-lived and consequently more efficient; it parasitized 144.3 larvae and killed 90.1 larvae. In a second step, we also explored the effect of T. absoluta larvae instar on parasitism by S. sp. nr. japonicus and subsequent development of the parasitoid offspring. Best results were obtained with the third larvae instar with a higher number of offspring produced, bigger individuals and a higher proportion of females. Our results support the hypothesis that the two species are good candidates for biological control programs targeting T. absoluta in Europe.     

Natural enemies of the South American moth, Tuta absoluta, in Europe, North Africa and Middle East, and their potential use in pest control strategies

The South American tomato leafminer, Tuta absoluta Meyrick (Lepidoptera: Gelechiidae), is an invasive Neotropical pest. After its first detection in Europe, it rapidly invaded more than 30 Western Palaearctic countries becoming a serious agricultural threat to tomato production in both protected and open-field crops. Among the pest control tactics against exotic pests, biological control using indigenous natural enemies is one of the most promising. Here, available data on the Afro-Eurasian natural enemies of T. absoluta are compiled. Then, their potential for inclusion in sustainable pest control packages is discussed providing relevant examples. Collections were conducted in 12 countries, both in open-field and protected susceptible crops, as well as in wild flora and/or using infested sentinel plants. More than 70 arthropod species, 20 % predators and 80 % parasitoids, were recorded attacking the new pest so far. Among the recovered indigenous natural enemies, only few parasitoid species, namely, some eulophid and braconid wasps, and especially mirid predators, have promising potential to be included in effective and environmentally friendly management strategies for the pest in the newly invaded areas. Finally, a brief outlook of the future research and applications of indigenous T. absoluta biological control agents are provided.     

Feeding and mating behaviour of Chinese citrus fly Bactrocera minax (Diptera,Tephritidae) in the field

The Chinese citrus fly, Bactrocera minax, is a major tephritid fruit fly pest that infests Citrus spp. fruits. The pest was removed from the national quarantine pest list in China in 2009 owing to its wide spread across the country, and it is currently considered a major threat to citrus industry in Asia. The frequent high infestation levels of B. minax in China emphasize the need for a more comprehensive understanding of its biology and ecology so that more efficient control measures can be developed and applied. In the framework of developing a sterile insect technique program against B. minax, we studied the feeding and mating activities of B. minax in situ (Citrus orchards and surrounding habitats) through open field surveys and video recordings. In the pre-oviposition period, sexually immature adults largely foraged for food (e.g. honeydew from aphids, nectar and sooty mould) on non-host plants. Then, sexually mature adult flies shifted to lick sooty moulds, bird faeces and, to a lesser extent, an unknown substance on the Citrus leaves and fruits during the mating and oviposition periods. Finally, during the post-oviposition period, the flies were observed feeding on ooze from grapes. The mating behaviour patterns of B. minax in the field were described as follows: first, the male established its territory close to the potential oviposition substrate (Citrus fruit), second, the female landed on the fruit and began inspection and ovipositor boring behaviour on the fruit surface (no male courtship observed e.g. wing vibration), and third, the male mounted and copulated with the female. The present study shed light on the feeding ecology and mating behaviour of B. minax in the field; this knowledge will facilitate development of better management strategies against this tephritid fly.     

For sex and more: attraction of the tephritid parasitoid Psyttalia concolor (Hymenoptera: Braconidae) to male sex pheromone of the olive fruit fly,Bactrocera oleae

The braconid parasitoid Psyttalia concolor foraging for larvae of Bactrocera oleae (Diptera: Tephritidae) uses olfactory cues from the larval microhabitat. However, it could rely on the sex pheromones of adults of its host, since B. oleae mating leks usually occur on olive plants and a high number of infested fruits can be easily located in their close proximity. We quantified the behavioural responses of P. concolor towards different doses of the two major sex pheromone components of B. oleae, the female-borne 1,7-dioxaspiro[5.5]undecane (DSU) and the male-borne (Z)-9-tricosene (ZT). Results showed that P. concolor females and males were attracted only to the highest amounts of ZT (10 B. oleae male equivalents), regardless of the mating status. Wasps remained longer on the surfaces treated with high ZT amounts over the control. P. concolor females could exploit the ZT produced by lekking olive fruit fly males as a foraging kairomone. This could allow them to rapidly track B. oleae-infested olive plants, thus raising their chances to locate host larvae during their lifespan. On the other hand, the perception of ZT by P. concolor males could raise their chances to locate receptive females emerging from parasitised B. oleae pupae or also ovipositing in olive fruits. This study increases the knowledge of the reproductive biology of P. concolor, highlighting a case of chemical espionage in which a sex pheromone component from adult stages of the host is exploited both as a foraging kairomone by female parasitoids and as a sexual kairomone by male wasps.     

Male multiple matings and reproductive success in commodity-adapted strains of <Emphasis Type="Italic">Sitophilus oryzae</Emphasis>

Multiple matings occur in many species of stored-grain insect pests, such as the rice weevil Sitophilus oryzae (L.), with both female and male mating more than once and with more than one partner. Multiple female mating in S. oryzae increased lifetime fecundity by extending the period of time progeny were produced, but consequences of multiple male mating in S. oryzae were not yet studied although it is likely to increase male fitness by increasing offspring production. Here, the effects of polygynous mating on male mating behavior, success, and fitness were assessed in two strains of S. oryzae, one adapted to barley and another to wheat. Two insect strains were considered because they may differ in response depending on the host grain, which present distinct nutritional value to the insects. Mating by pairs formed between the two strains did not impact mating success, but wheat-adapted females exhibited longer mating duration, which was positively correlated with progeny production. Wheat-adapted males exhibited higher fertility than barley-adapted males. When male multiple matings were considered in successive polygynous matings, late matings led to lower non-cumulative values of progeny production, but higher cumulative performance, and wheat-adapted S. oryzae always performed better. Thus, male fitness and grain losses in wheat are higher than in barley, even when S. oryzae was adapted to the latter.     

Genetic patterns as possible factors causing population cycles in oak leafroller moth,Tortrix Viridana L.

The genetic patterns and their possible effects on population dynamics were studied in Tortrix viridana L. (Lepidoptera: Tortricidae) – a serious pest of oaks in Europe. The following empiric results were obtained: (1) The trends revealed at the Est-4 and Pts-4 loci were directly related to this insect's population dynamics. Heterozygosity at the loci was high during the outbreak phase and low during the population decline and depression phase. In all the cases genetic changes preceded the changes in population density. (2) Plant–larva interactions resulted in strong gene–environment relationships which indicated that carriers of alternative Pts-4 and Est-4 genotypes inhabited different food micro-niches. These gene–environment relationships were shown to be caused by the differential larvae survival. (3) Natural selection (differential survival) at the larva stage worked in favor of the same genotypes in both the males and females within each of the micro-populations. These genotypes further showed, longer body length in adults, and higher fertility in comparison to those genotypes which were `unfit' during the larva phase. (4) Body size appeared to be subjected to sexual selection as well. Females always tended to mate with larger males. Male's mate selection was related to the phase of the population cycle with smaller females having sexual advantage during the outbreak phase and larger females being selected prior to the population decline and, probably, during the depression phase. This mating system based on body size evoked assortative mating for the Est-4 and, probably, Pts-4 genotypes. It was negative-like during an outbreak, and positive at population decline and during depression phase. These results allowed the construction of a model, probably, describing the population cycles in T. viridana. During outbreaks, genetic heterogeneity was high, and numerous two-locus genotypes prevailed in many different food micro-niches. This strategy thus optimized the entire food resource available to the insect. Conversely, when the heterozygosity was low, only the micro-niches of two-locus homozygotes were filled generating heavy competition among the larvae, leading to a high larval mortality. Assortative mating at allozymic loci is suggested to be the main factor regulating genetic heterogeneity in T. viridana. This mechanism could be incorporated into predictive models used to study the population dynamics of T. viridana.     

The use of water traps and presence of spermatophores to evaluate mating disruption in the almond moth, Ephestia cautella, during exposure to synthetic sex pheromone

The purpose of the study was to verify the efficacy of a mating-disruption system (MD) applied in a confectionary factory infested by almond moths, Ephestia (Cadra) cautella (Walker), using pheromone traps and the presence of spermatophores in females caught with water traps. Results obtained confirmed that water is a considerable attractant for E. cautella, as a great number of males and females were caught. The presence of spermatophores in females allowed determination of mating status: most captured females were mated; in the area where MD was applied to the percentage of unmated females was lower as compared to the control area (the proportion of unmated females was much higher in the control area). In an integrated pest management programme, the combined use of MD and water traps eliminates large numbers of male and female almond moths. This information will be useful in developing strategies for suppressing E. cautella infestation.     

Potential for combined use of parasitoids and generalist predators for biological control of the key invasive tomato pest Tuta absoluta

The tomato leafminer Tuta absoluta (Meyrick) (Lepidoptera: Gelechiidae) has recently invaded Mediterranean countries and is a major pest in tomato crops. Trichogrammatid oophagous parasitoids have shown promising potential for controlling the pest before the yield decreases in the greenhouse. In protected tomato crops (greenhouse), mirid predators are commonly used for biological control of whiteflies and they also prey on T. absoluta. These predators do not attack Trichogramma adults but they may partially decrease the overall impact of parasitoids on T. absoluta if intraguild predation (IGP) occurs on parasitized eggs. Under laboratory conditions, we tested if the mirid predator Macrolophus pygmaeus shows preference between parasitized and unparasitized T. absoluta eggs. We also tested if the predator reduces the number of parasitized eggs on caged tomato plants (microcosms) and assessed the efficacy of natural enemies used alone or together in limiting T. absoluta populations. We found that IGP is inflicted on the parasitoid Trichogramma achaeae by M. pygmaeus and that the risk of IGP depends on the developmental stage of T. achaeae inside the egg because the larva is at risk mostly early in its development (when parasitized egg is still yellow). In addition, we observed that non-consumptive events, likely probing of the predator on parasitized eggs, may induce mortality in parasitoid offspring without actual feeding on parasitized eggs. However, both IGP and non-consumptive events decreased when the predator was not confined with parasitized eggs in small arenas. Despite negative effects of the predator to the parasitoid, results demonstrate that adding Trichogramma parasitoids may significantly increase the level of control of the pest over what could be attained when only the mirid predator M. pygmaeus is present on tomato. Implications of results are discussed regarding potential of these natural enemies for biological control of T. absoluta in greenhouse tomato crops.     

Development of natural waxes dispensers for pheromones and use in mating disruption of the ambrosia beetle <Emphasis Type="Italic">Megaplatypus mutatus</Emphasis> in poplar (<Emphasis Type="Italic">Populus</Emphasis> spp) plantations

Megaplatypus mutatus (= Platypus mutatus) (Chapuis) is an ambrosia beetle native to South America that attacks live trees, mining deeply into the xylem through large tunnels. This activity weakens the structural integrity of the tree, causing severe stem-breakage and mortality. Attacks are initiated by pioneer males that select a host tree and build short nuptial galleries, to which they attract females using a sexual pheromone. Previously, we showed the potential for the strategy of pheromone-mediated mating disruption of M. mutatus in commercial poplar and hazelnut plantations in South America and Europe using polyethylene reservoir dispensers for pheromones. In the present work we replaced the polymeric reservoir dispensers by monolithic dispensers made by dispersion of the pheromone in natural waxes and the addition of kaolin and we found that: prior to pheromone deployment, the mean number of galleries per tree did not differ significantly between the control and treated plots and the same was observed after the mating disruption treatment for the control plot but not for treated plots, where the mean number of galleries were reduced. These findings confirm that mating disruption is a viable tool for management of M. mutatus in poplar plantations. Using natural wax dispensers has obvious advantages from an environmental point of view.     

Reflections on structure and function of pheromone glands in storage insect species

Several polyphagous coleopteran and lepidopterous species, presently known as storage insects, have presumably evolved from free-living ancestral species, being capable of growth and reproduction on stored, desiccated and often nutritionally deficient foodstuffs. These potentially harmful insect species have probably adapted themselves to the newly acquired storage biotope by means of a well-developed sensory equipment serving food acquisition, aggregation and mate finding.Information by molecules may be communicated among the individuals of an insect species by means of relatively volatile pheromones (Greek, pher=convey) being emitted by exocrine glands and mainly carried by moving air to the sensilla of responsive individuals, or among the internal organs of an insect by means of relativelynonvolatile hormones (Greek, horma=impel), secreted fromendocrine glands and transported by the haemolymph to the receptors of target organs. It was postulated that pheromones were among the first chemical messengers utilized during evolution of animal behaviour, and that the pheromones of primitive protozoans could have been precursors of the hormones of metazoans. Hormones of the neurosecretory cells and corpora allata were found to induce sex pheromone biosynthesis in femaleTenebrio molitor, while dietary intake of a juvenile hormone analogue was shown to significantly enhance the production of aggregation pheromones in the males of certain silvanid and cucujid species.Aggregation pheromones are usually produced by the longlived and feeding males of several coleopteran species (Table 2) which deposit those chemical messengers to the substrate, where they induce the formation of bisexual assemblies supporting feeding, mating and reproduction. Sex pheromones are mostly produced by the short-lived and non-feeding females of several coleopteran and lepidopterous species (Table 2); females of those species usually release their sex pheromones to the air space during calling, and thus attract conspecific males for mating (Fig. 5 a–c).In some dermestid species, pheromone emission differs from the above scheme. Females of the short-lived and non-feedingTrogoderma granarium andT. inclusum release a phromone acting as a sex attractant for conspecific males and—in synergistic combination with tactile stimuli—as an assembling scent for conspecific females (Figs. 1 a, b, 2 and Table 1), females of the short-lived and feedingAntbrenus verbasci, Attagenus megatoma andAtt. elongatulus produce a sex pheromone for conspecific males, while females of the long-lived and feedingAn. scrophulariae emit a sex pheromone which lures conspecific males.Males of the long-lived and non-feeding bruchid speciesAcanthoscelides obtectus release a sex pheromone which attracts conspecific females. Androconial pheromones are discharged during courtship from the alar scales and abdominal tufts found in males of several microlepidopteran species (Phycitidae) includingAnagasta kuebniella, Cadra cautella, Ephestia elutella andPlodia interpunctella (Fig. 6 b–c); those aphrodisiac pheromones are known to enhance the specific responsiveness of the females to their mates. Electrophysiological recordings revealed that aggregation pheromones elicit considerable receptor potentials in the antennal olfactory sensilla of both sexes, whereas sex pheromones induce high receptor potentials in the antennal olfactory sensilla of one sex only. It was assumed that aggregation pheromones may be the evolutionary precursors of sex pheromones.Pheromone-producingexocrine glands are essentially groups of modified epidermals cells which are found in different body regions of male and/or female storage insect species. A simple pheromone gland, consisting of a single layer of adjacent secretory cells beneath the endocuticle of the 5th visible abdominal sternite, occurs in femaleTrogoderma granarium (Fig. 3 a). A more complex design, comprising an intra-abdominal semiglobular pheromone gland with numerous secretory cells being connected to tubuli which lead to an invaginated cuticular cribellum, is available in maleDermestes maculatus (Figs. 3 c, d and 4 c). The cribellum, provided with a caudally curved brush of fluted brisles, occurs in the centre of the 4th visible abdominal sternite (Figs. 4 a, b and 7 b). An apodemous exocrine gland is found in the lumen of the second abdominal segment of femaleLasioderma serricorne (Fig. 3 b). This lobate gland comprises many secretory cells, being connected by numerous tubuli to a sheath-like conical duct enveloping a V-shaped skeletal apodeme, which terminates in the abdominal tip. In maleTribolium castaneum, the secretory cells of both pheromone glands are connected by tubuli to two cribella, being densely covered by fluted bristles, and found in the femora of both forelegs (Fig. 7 a). Females of the phycitid speciesAnagasta kuebniella, Cadra cautella, Ephestia elutella andPlodia interpunctella are equipped with an intersegmental pheromone gland, situated between the 8th and 9th abdominal segment near the genital opening. The exocrine gland of the four moth species consists of a single layer of columnar secretory cells, lined by a spongy cuticle which seems to be permeable to the sex pheromone (Fig. 6 a). The latter is disseminated by calling females (Fig. 5 a, b) while their exocrine glands are widely exposed. Males of the above phycitid species are furnished with alar and abdominal androconia which become exposed during courtship and discharge aphrodisiac pheromones. The base of each of the androconial bristles and scales is immersed to an underlying unicellular, pheromone-producing gland (Fig. 6 d, e). The aphrodisiac pheromones, being secreted by the above glandular cells, are passing the lumen and walls of the bristles and scales, and evaporate from the surface of the latter. For example, malePlodia interpunctella possess 2 pairs of scent tufts (a small and a large one) on both sides of the 8th abdominal tergiet as well as 2 pairs of scent tufts (a small and a large one) near the base of the costal margin of the forewings (Fig. 6 b, c). Females of several phycitid species respond to the aphrodisiac pheromone of conspecific males by a pronounced readiness to mate.In the course of time, about 3 dozens of insect species (3/4 coleopteran and 1/4 lepidopterous species) have undergone sympatric speciation by sharing desiccated food in stores as a common habitat. Fertile matings between such heterogeneous species are often prevented by morphological and anatomical incompatibilities as well as physiological and behavioural barriers. Most of the species living in the storage habitat are reproductively isolated due to the molecular structure and blend composition of their pheromones (Table 2). Interestingly, some species (listed below) deviate from the majority by sharing the structure of their main pheromone components (mentioned in parenthesis), and are thus poorly separated: the curculionidsSitophilus oryzae andS. zeamais ((4S,5R)-5-hydroxy-4-methyl-3-heptanone), the tenebrionidsTribolium castaneum andT. confusum ((4R,8R)-dimethyldecanal) as well as the dermestidsTrogoderma inclusum andT. variabile ((R,Z)-14-methyl-8-hexadecenal). Theinsufficient reproductive isolation of the above species is compensated, i.a., by additional availability of a sex pheromone in femaleTribolium confusum, by different calling periods and emission rates of (R,Z)-14-methyl-8-hexadecenal in females of the forementionedTrogodema species.Trogoderma glabrum andT. granarium areincompletely isolated by sharing (R,E)-14-methyl-8-hexadecenal as a pheromone component; they are indeed capable of cross-mating, but produce sterile hybrids. Moreover, maleOryzaepbilus mercator andO. surinamensis incorporate (Z,Z)-3,6-dodecadien-11R-olide as a common chiral component to their aggregation pheromones. The females of 5 phycitid species share (Z,E)-9,12-tetradecadien-1-yl acetate as their main pheromone component, while they are reproductively separated by additional emission of (Z)-9-tetradecen-1-yl acetate and (Z,E)-9,12-tetradecadien-1-ol as secondary pheromone components, by the production of different androconial pheromones in conspecific males as well as different circadian calling activities.In the course of their research engagement on pheromones of storage insect and mite species (during the past 2.5 decades), the authors enjoyed fruitful collaboration with several renowned investigators working in Athens, Berlin, Hamburg, New York, Pantnagar, Tiantsin, Tokyo, Wisconsin, Yokohama and Zürich (chapter 6).Motto ...In addition to the amazing range of physiological activities of which it is capable during the process of moulting and cuticle formation, the epidermal cell is potentially an embryonic cell, with latent powers of differentiating in several different directions. The ordinary epidermal cell may divide to give rise to a pair of oenocytes. It may divide into four and produce a dermal gland cell with associated cells that form the glandular duct. Or the four daughter cells may differentiate into the bristle-forming and socket-forming cells which give rise to the sensillum and into the sense cell with its neurilemma cell both of which grow inwards to become a part of the central nervous system ...V B. Wigglesworth, 1959With 2 tables and 7 figuresDedicated to the memory of Prof. Dr. Sir Vincent BrianWigglesworth who died on February 12th, 1994.     

Asymmetry of mating behaviour affects copulation success in two stored-product beetles

Lateralization (i.e. left–right asymmetries in the brain and behaviour) has been documented in all vertebrate classes, while evidences for invertebrates are limited. To the best of our knowledge, there is no information about behavioural asymmetries in the order Coleoptera. In this research, we investigated the lateralization of mating traits in two major pests of stored products: the rice weevil, Sitophilus oryzae (Coleoptera: Curculionidae), and the confused flour beetle, Tribolium confusum (Coleoptera: Tenebrionidae). Both T. confusum and S. oryzae males showed population-level left-biased copulation approaches of potential mates. Interestingly, T. confusum and S. oryzae males performing left-biased copulation attempts achieved higher mating success over right-biased males. Furthermore, S. oryzae males periodically exhibited a typical head wagging behaviour, which consists of waving the rostrum laterally across the female thorax and then resting the rostrum on the mid thorax. This behaviour was right-biased, even in the majority of males that previously showed left-biased copulation attempts. The quantification of mating displays could allow comparisons with other strains, in order to evaluate the impact of a given host or of the rearing methods on the mating traits of S. oryzae and T. confusum. Overall, this is the first report of lateralization of mating traits in Coleoptera. Furthermore, this research adds basic knowledge to the reproductive behaviour of S. oryzae and T. confusum.     

Sterile insect technique and <Emphasis Type="Italic">Wolbachia</Emphasis> symbiosis as potential tools for the control of the invasive species <Emphasis Type="Italic">Drosophila suzukii</Emphasis>

Drosophila suzukii, a vinegar fly originated from Southeast Asia, has recently invaded western countries, and it has been recognized as an important threat of a wide variety of several commercial soft fruits. This review summarizes the current information about the biology and dispersal of D. suzukii and discusses the current status and prospects of control methods for the management of this pest. We highlight current knowledge and ongoing research on innovative environmental-friendly control methods with emphasis on the sterile insect technique (SIT) and the incompatible insect technique (IIT). SIT has been successfully used for the containment, suppression or even eradication of populations of insect pests. IIT has been proposed as a stand-alone tool or in conjunction with SIT for insect pest control. The principles of SIT and IIT are reviewed, and the potential value of each approach in the management of D. suzukii is analyzed. We thoroughly address the challenges of SIT and IIT, and we propose the use of SIT as a component of an area-wide integrated pest management approach to suppress D. suzukii populations. As a contingency plan, we suggest a promising alternative avenue through the combination of these two techniques, SIT/IIT, which has been developed and is currently being tested in open-field trials against Aedes mosquito populations. All the potential limiting factors that may render these methods ineffective, as well as the requirements that need to be fulfilled before their application, are discussed.