Gabriella Bonsignori

Courtship and mating behaviour in the fruit fly parasitoid Psyttalia concolor (Szépligeti) (Hymenoptera: Braconidae): the role of wing fanning.

Psyttalia concolor is a parasitoid of fruit flies (Tephritidae) which is used to control the olive fruit fly (Bactrocera oleae). Detailed knowledge of its reproductive biology is required to optimise mass rearing conditions and use in biological control. In this study, the mating behaviour of P. concolor was investigated in order to understand the factors that can influence the success of male mating, using both high-speed video and biological assays. P. concolor males were more likely to be successful in mating during the early morning as opposed to the afternoon, and their courtship behaviour was not affected by the female mating status (i.e. virgin or mated). Wing fanning and copulation attempts were also frequently displayed among males, but male mating status did not influence male–male courtship behaviour. Video data revealed that during wing fanning, male wings were kept raised and moved rhythmically in a dorsoventral fashion. Frequency, pulse duration and interpulse interval of the fanning males during female courtship differed significantly in successful mating attempts compared to unsuccessful ones. Wingless males had significantly lower mating success compared to winged males, suggesting that wing fanning increases the likelihood of attracting a mate. Overall, the study increases the knowledge of the reproductive biology of P. concolor and suggests the importance of fanning behaviour among the range of sensory modalities used by this parasitoid in intra-specific communication.

Male Wing Vibration in the Mating Behavior of the Olive Fruit Fly Bactrocera oleae (Rossi) (Diptera: Tephritidae)

The olive fruit fly, Bactrocera oleae (Diptera: Tephritidae), is a worldwide pest of olive fruits. To date, the mating behavior of this tephritid has not been fully clarified. Little has been reported regarding the characteristics and behavioral role of B. oleae male wing vibration. This study provides a detailed description of male wing vibration, recorded by a high-speed video camera and compared with a frame-by-frame analysis, prior to successful and unsuccessful matings. Experimental evidence is given of the importance of male wing vibration during courtship for successful mating. Firstly, when the males did not perform wing vibration, but simply jumped onto the female and immediately attempted to copulate, no successful matings were registered. Secondly, when the male’s wings were removed, the probability of successful mating was significantly reduced. Thirdly, the frequency and pulse duration of the male wing vibration during courtship were higher in successful matings than in unsuccessful ones. Lastly, a wing sexual dimorphism was found: length and total wing area were significantly higher among males. Overall, our research increases the knowledge of the reproductive behavior of B. oleae, by suggesting the importance of wing vibration among the range of sensory modalities used by this tephritid in sexual communication.

The green leafhopper, Cicadella viridis (Hemiptera, Auchenorrhyncha, Cicadellidae), jumps with near-constant acceleration

SUMMARY Jumping insects develop accelerations that can greatly exceed gravitational acceleration. Although several species have been analysed using different tools, ranging from a purely physical to a morpho-physiological approach, instantaneous dynamic and kinematic data concerning the jumping motion are lacking. This is mainly due to the difficulty in observing in detail events that occur in a few milliseconds. In this study, the behaviour of the green leafhopper, Cicadella viridis, was investigated during the take-off phase of the jump, through high-speed video recordings (8000 frames s−1). We demonstrate that C. viridis is able to maintain fairly constant acceleration during overall leg elongation. The force exerted at the foot–ground interface is nearly constant and differs from the force expected from other typical motion models. A biomechanical model was used to highlight that this ability relies on the morphology of C. viridis hind legs, which act as a motion converter with a variable transmission ratio and use the time-dependent musculo-elastic force to generate a nearly constant thrust at the body–ground interface. This modulation mechanism minimizes the risk of breaking the substrate thanks to the absence of force peaks. The results of this study are of broad relevance in different research fields ranging from biomechanics to robotics.

The production of female sex pheromone in Bactrocera oleae (Rossi) young males does not influence their mating chances

In Bactrocera oleae females attract males, which is in contrast to the majority of Tephritidae. However, the major component of the secretion of the female rectal ampulla glands, 1,7‐dioxaspiro‐[5,5]‐undecane (DSU), was also isolated from the glands of young males. The DSU produced by females and young males attracts males, but not females. In this study, we investigated the role of the production of DSU in young males. The mating performances of young and old males were evaluated, as well as the male‐male courtships by old males oriented at young and old males. Young males were found not to have a mating advantage. Young males were courted more by other males. Frame‐by‐frame analysis of male wing vibrations showed that this behavior did not differ when oriented at females and young males, highlighting that young males are perceived as females by the courting males. Overall, the production of DSU in young B. oleae males did not seem to be a case of female chemical mimicry. The hypothesis that young olive fruit fly males could benefit indirectly from the DSU production, simply distracting mature males away from females, is discussed.

Male Wing Fanning Performance During Successful and Unsuccessful Mating in the Parasitic Wasp Lariophagus distinguendus Förster (Hymenoptera: Pteromalidae)

Lariophagus distinguendus Förster (Hymenoptera: Pteromalidae) is a generalist solitary ectoparasitoid that parasitizes the immature stages of at least 11 foodstuff beetles from five families, including species developing in the seeds of Poaceae, Fabaceae and in dried natural products. In L. distinguendus, male wing fanning is a key phase in the courtship sequence and is elicited by a female-borne sex pheromone. However, studies aimed at understanding the role of wing vibration in L. distinguendus during courtship are lacking. In this research, the wing fanning performances of the L. distinguendus male towards other females and males were analyzed through high-speed video recordings and examined in relation to mating success. Only small differences were found between the fanning characteristics displayed toward females and young males, highlighting that young males are really perceived as females by older males. Male mating success was affected by the quality of the wing fanning in the courtship phase. Indeed, both immediately after the female perception and during mating attempts, fanning before a successful courtship differed compared to wing fanning performed prior to an unsuccessful courtship in terms of their mean frequency, but not their amplitude. Overall, our work increases knowledge of the courtship behavior of L. distinguendus and highlights the crucial importance of wing fanning among the range of sensory modalities used in the sexual communication of this parasitic wasp.

Behavioural and electrophysiological responses of the olive fruit fly, Bactrocera oleae (Rossi) (Diptera: Tephritidae), to male- and female-borne sex attractants

In the olive fruit fly, Bactrocera oleae, females attract males by producing 1,7-dioxaspiro[5.5]undecane (olean), the main component of the sex pheromone secreted by rectal glands. It has been recently demonstrated that males are able to produce (Z)-9-tricosene (muscalure) in rectal glands, a compound that selectively attracts females. In this study, a male grooming reaction that may transfer the male-borne compounds from rectal to urotergal glands was observed, suggesting that urotergal glands could be involved in B. oleae sexual communication. GC/MS, EAG, GC/EAD analyses and behavioural assays were carried out to compare the role of male rectal and urotergal glands during courtship. In both male glands, olean and muscalure amounts were age dependent. Extracts of rectal glands contained higher amounts of olean and/or muscalure than urotergal ones. Extracts of rectal and urotergal glands of males and females elicited EAG responses in both sexes. GC/EAD showed that female EAG response to male rectal extracts was mainly due to olean and muscalure. Synthetic compounds evoked EAG dose-dependent responses in both sexes, and the EAG response to muscalure was higher as compared to olean. Rectal and urotergal glands from old males were able to attract females, while urotergal glands from young males attracted only males. Overall, our results add knowledge to the mating system of B. oleae, giving first evidences on the electrophysiological activity of muscalure towards both sexes, as well as on the involvement of male urotergal glands in the chemical sexual communication of this pest.

Jumping mini-robot with bio-inspired legs

This paper presents a bio-inspired concept for an autonomous centimeter-scale robot for locomotion on un-even terrains with bionic legs. Our previous work, the jumping robot “GRILLO I” (Fig. 1A), is firstly introduced, as well as its limitations. For improving the performance of this prototype, we made biological observations on jumping insects by means of a high speed camera. It was found that the legs configuration let map muscle-like force into a constant force at feet-ground interface, which represents an optimum design for jumping. That gives us the bionic inspiration to redesign the legs that can reproduce the dynamic characteristics of insect jumping. Based on this idea, a new jumping robot prototype, GRILLO II (Fig. 1B), is then presented, as well as jumping details measured by the high speed camera and accelerometer.

May the wild male loose? Male wing fanning performances and mating success in wild and mass-reared strains of the aphid parasitoid Aphidius colemani Viereck (Hymenoptera: Braconidae: Aphidiinae)

Aphidius colemani Viereck (Hymenoptera: Braconidae) is a pan-tropical broadly oligophagous endoparasitoid of many aphids of economic importance, including Aphis gossypii Glover and Myzus persicae (Sulzer). While the trophic interactions occurring among A. colemani and its hosts have been extensively studied, little is known about the male- and female-borne cues that guide mating dynamics. Male wing fanning has been found to play a key role in A. colemani courtship, as successful mounting of females without initial wing fanning has never been observed. In this research, we analyzed wing fanning performance and mating ability of males from three different strains of A. colemani: wasps commercially mass-reared on A. gossypii, wild wasps from parasitized A. gossypii, and wild wasps from parasitized Aphis nerii Boyer de Fonscolombe. Results showed that virgin females did not rely on particular male fanning features during mate choice. Moreover, when A. colemani individuals developed on A. gossypii, no major differences were detected in courtship and mating ability between field collected and mass-reared wasps. In contrast, courtship performance and mating success varied between wild A. colemani males reared on different hosts, with those developing on A. nerii having lower quality wing fanning performance during the mounting attempt phase, and reduced ability to compete for females with other males reared on A. gossypii.

Cumulative annual dung beetle diversity in Mediterranean seasonal environments

Species diversity assessments should consider the dynamic nature of ecological communities, especially in highly seasonal ecosystems. Here we provide a comprehensive framework for analysing seasonal changes in species composition, richness and diversity in two local dung beetle (Coleoptera: Scarabaeoidea: Aphodiidae, Geotrupidae, and Scarabaeidae) communities from Western Tuscany (Italy), in the Mediterranean ecoregion. We test whether, in this highly seasonal region, cumulative annual diversity is an oversimplification of well differentiated seasonal communities. Data were obtained through repeated standardised samples collected regularly over an entire year. We clearly identify different summer and winter communities at each site based on species composition and abundance. Seasonal richness and diversity values are different from the cumulative annual values, as a consequence of beta diversity between seasons, and some dung beetle species are identified as idiosyncratic of each particular season. Both ecological (niche partitioning) and biogeographical factors are suggested as drivers of these temporal variations. Thus, because local inventories of fauna that include records over long time periods actually reflect situations where coexistence and interactions are unlikely to occur, highly seasonal sites must be viewed as having temporally differentiated communities in order to reach feasible and reliable baselines for local diversity assessments.

Bioinspired Jumping Locomotion in Small Robots: Natural Observation, Design, Experiments

In this paper we present the results of biological observation on jumping insects, and how to relate them to legged robots. In particular, by observing jumping Leafhoppers with a high speed camera, we found out how the legs’ configuration during take-off let the insect map muscle-like force into constant force, which represents an optimal design for jumping. We then implemented the same design in a 20 grams jumping prototype, verifying the optimality of such bio-inspired solution for locomotion of a small robot.