Drilling into solid substrates with slender beam-like structures is a mechanical challenge, but is regularly done by female parasitic wasps. The wasp inserts her ovipositor into solid substrates to deposit eggs in hosts, and even seems capable of steering the ovipositor while drilling. The ovipositor generally consists of three longitudinally connected valves that can slide along each other. Alternative valve movements have been hypothesized to be involved in ovipositor damage avoidance and steering during drilling. However, none of the hypotheses have been tested in vivo. We used 3D and 2D motion analysis to quantify the probing behavior of the fruit-fly parasitoid Diachasmimorpha longicaudata (Braconidae) at the levels of the ovipositor and its individual valves. We show that the wasps can steer and curve their ovipositors in any direction relative to their body axis. In a soft substrate, the ovipositors can be inserted without reciprocal motion of the valves. In a stiff substrate, such motions were always observed. This is in agreement with the damage avoidance hypothesis of insertion, as they presumably limit the overall net pushing force. Steering can be achieved by varying the asymmetry of the distal part of the ovipositor by protracting one valve set with respect to the other. Tip asymmetry is enhanced by curving of ventral elements in the absence of an opposing force, possibly due to pretension. Our findings deepen the knowledge of the functioning and evolution of the ovipositor in hymenopterans and may help to improve man-made steerable probes.Diachasmimorpha longicaudata | ovipositor kinematics | buckling avoidance | spatial probing | minimally invasive probe F rom a mechanical perspective, it is very difficult to drill into a solid substrate with a very thin probe, because it can easily bend and break. Parasitic wasps, however, do this regularly when they use their slender ovipositors to search for hosts in solid substrates, such as fruits or even wood (1-3).The general morphology of the ovipositor is similar across all wasp species (4, 5); it consists of four elements, called valves, of which two are often merged such that three functional valves remain (Fig. 1). In most species, the distal part of the ovipositor is morphologically distinct (3, 6), which we will refer to as the tip. The valves can slide along each other (5, 7) and do not get dislocated under natural conditions, because they are longitudinally connected via a tongue-and-groove mechanism (5, 8-10). The ovipositor and the "wasp waist," a constriction of the body between the first and second abdominal segment (11), are essential in probing behavior and are therefore considered to be instrumental in the evolution of the order (11-15). The shape, structure, and mechanical properties of the ovipositors are putatively adapted to the substrates into which the animals need to probe (6,(16)(17)(18), and because both substrates and hosts are so diverse, this might have resulted in high species diversification of the hymenopterans (13,14). Howeve...
Background Monitoring of malaria vectors is important for designing and maintaining effective control interventions as changes in vector-feeding habits can threaten the efficacy of interventions. At present, human landing catches remain the most common method for monitoring malaria vectors of the Anopheles punctulatus complex, including the Anopheles farauti group. The aims of this study were to evaluate the efficacy of different lures and fan-powered traps, including an odour blend that has been demonstrated to be attractive to African anophelines, in Queensland, Australia. Methods To evaluate the performance of different lures in trapping An. farauti in the field, four Suna traps were baited with either: CO 2 -alone, a synthetic lure (MB5 or BG-Lure) plus CO 2 , or a human odour plus CO 2 and set in the field in Cairns, eastern Australia. A second study evaluated the performance of four traps: a Passive Box trap, BG-Suna trap, BG-Sentinel 2 trap, and BG-Bowl trap, for their ability to trap An. farauti using the best lure from the first experiment. In both experiments, treatments were rotated according to a Latin square design over 16 nights. Trapped mosquitoes were identified on the basis of their morphological features. Results BG-Suna traps baited with CO 2 alone, a BG-Lure plus CO 2 or a natural human odour plus CO 2 captured comparable numbers of An. farauti . However, the number of An. farauti sensu lato captured when the MB5 lure was used with CO 2 was three times lower than when the other odour lures were used. The BG-Sentinel 2 trap, BG-Suna trap and BG-Bowl trap all captured high numbers of An. farauti , when baited with CO 2 and a BG-Lure. The morphological condition of captured mosquitoes was affected by mechanical damage caused by all fan-powered traps but it was still possible to identify the specimens. Conclusions The BG-Sentinel 2 trap, BG-Suna trap and the BG-Bowl trap captured high numbers of An. farauti in the field, when equipped with CO 2 and an odour lure (either the BG-Lure or a natural odour). The most important attractant was CO 2 . This study shows that fan-powered traps, baited with CO 2 plus an appropriate odour lure, can be a promising addition to current vector monitoring methods in the Southwest Pacific.
Zoonotic Plasmodium infections in humans in many Southeast Asian countries have been increasing, including in countries approaching elimination of human-only malaria transmission. Most simian malarias in humans are caused by Plasmodium knowlesi, but recent research shows that humans are at risk of many different simian Plasmodium species. In Southeast Asia, simian Plasmodium species are mainly transmitted by mosquitoes in the Anopheles leucosphyrus and Anopheles dirus complexes. Although there is some evidence of species outside the Leucosphyrus Group transmitting simian Plasmodium species, these await confirmation of transmission to humans. The vectors of monkey malarias are mostly found in forests and forest fringes, where they readily bite long-tailed and pig-tailed macaques (the natural reservoir hosts) and humans. How changing land-uses influence zoonotic malaria vectors is still poorly understood. Fragmentation of forests from logging, agriculture and other human activities is associated with increased zoonotic Plasmodium vector exposure. This is thought to occur through altered macaque and mosquito distributions and behaviours, and importantly, increased proximity of humans, macaques, and mosquito vectors. Underlying the increase in vector densities is the issue that the land-use change and human activities create more oviposition sites and, in correlation, increases availably of human blood hosts. The current understanding of zoonotic malaria vector species is largely based on a small number of studies in geographically restricted areas. What is known about the vectors is limited: the data is strongest for distribution and density with only weak evidence for a limited number of species in the Leucosphyrus Group for resting habits, insecticide resistance, blood feeding habits and larval habitats. More data are needed on vector diversity and bionomics in additional geographic areas to understand both the impacts on transmission of anthropogenic land-use change and how this significant disease in humans might be controlled.
The epidemiology of human malaria differs considerably between and within geographic regions due, in part, to variability in mosquito species behaviours. Recently, the WHO emphasised stratifying interventions using local surveillance data to reduce malaria. The usefulness of vector surveillance is entirely dependent on the biases inherent in the sampling methods deployed to monitor mosquito populations. To understand and interpret mosquito surveillance data, the frequency of use of malaria vector collection methods was analysed from a georeferenced vector dataset (> 10,000 data records), extracted from 875 manuscripts across Africa, the Americas and the Asia-Pacific region. Commonly deployed mosquito collection methods tend to target anticipated vector behaviours in a region to maximise sample size (and by default, ignoring other behaviours). Mosquito collection methods targeting both host-seeking and resting behaviours were seldomly deployed concurrently at the same site. A balanced sampling design using multiple methods would improve the understanding of the range of vector behaviours, leading to improved surveillance and more effective vector control.
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