Attraction Versus Capture II: Efficiency of the BG-Sentinel Trap Under Semifield Conditions and Characterizing Response Behaviors of Male Aedes aegypti (Diptera: Culicidae)

Aedes aegypti (L.) is an important vector of viruses causing dengue, Zika, chikungunya, and yellow fever and as such presents a serious threat to public health in tropical regions. Control programs involving ‘rear and release’ of modified male Ae. aegypti are underway and require effective trapping methods for surveillance of both the released insects and the impacted wild mosquito population. The BG-Sentinel trap (BGS) is widely used in Ae. aegypti surveillance but its level of efficiency, that is, what proportion of the mosquitoes encountering the trap are captured, is unknown. This is especially true for male mosquitoes, the behavior of which is incompletely understood. We tested the efficiency of two versions of the BGS for capturing male Ae. aegypti under semifield conditions with and without CO2 and a human skin odor mimic lure and with these baits combined. A navy-blue BGS trap emitting CO2 and a human skin odor mimic captured 18% of the released male Ae. aegypti, with a capture efficiency of 9 % (of the total encounters with the trap). Male Ae. aegypti had multiple encounters with the BGS that did not result in capture; they crossed over the trap entrance without being captured or landed on the sides of the trap. Swarming behavior around the BGS was also recorded, even when only a visual cue was present. Understanding male Ae. aegypti behaviors during an encounter with the BGS can inform improvement of trap design and therefore capture efficiency for surveillance in control programs.

Attraction Versus Capture: Efficiency of BG-Sentinel Trap Under Semi-Field Conditions and Characterizing Response Behaviors for Female Aedes aegypti (Diptera: Culicidae)

Aedes aegypti (L.) is an important vector of viruses causing dengue, Zika, chikungunya, and yellow fever and as such is a threat to public health worldwide. Effective trapping methods are essential for surveillance of both the mosquito species and disease presence. The BG-Sentinel (BGS) is a widely used to trap Ae. aegypti but little is known of its efficiency, i.e., what proportion of the mosquitoes encountering the trap are captured. The first version of the BGS trap was predominantly white, and the current version is mostly navy blue. While this trap is often deployed without any olfactory lure, it can also be deployed with CO2 and/or a human skin odor mimic lure to increase capture rates. We tested the efficiency of capturing Ae. aegypti under semi-field conditions for the original white version without lures as well the blue version with and without various lure combinations. None of the configurations tested here captured 100% of the mosquitoes that encountered the trap. A navy-blue trap emitting CO2 and a skin odor mimic produced the highest capture (14% of the total insects in the semi-field cage), but its capture efficiency was just 5% (of mosquitoes encountering the trap). Mosquitoes often had multiple encounters with a trap that did not result in capture; they crossed over the trap entrance without being captured or landed on the sides of the trap. Understanding these behaviors and the factors that induce them has the potential to suggest improvement in trap design and therefore capture efficiency.

Development of a trap for collecting Cochliomyia hominivorax (diptera: caliphoridae) flies

The insect Cochliomyia hominivorax (Diptera: Caliphoridae) causes primary cutaneous myiasis, and the use of traps is an alternative to monitor this fly in the field. Thus, the objective of this work was to develop a low-cost trap for collecting C. hominivorax in the field. Three experiments were conducted, with six replications, in the experimental field of the Brazilian Agricultural Research Corporation (Embrapa - Agropecuária Oeste), in Ponta Porã, State of Mato Grosso do Sul, Brazil. Traps were developed using two-liter polyethylene terephthalate (PET) bottles cut in half, with 30 grams of bovine liver and water covering 90 % of the liver mass placed in the bottom half, using the upper half as a cover funnel to keep the captured flies in the bottom half. The experiments consisted of evaluations of different opening diameter of the trap entrance (3, 4, 6 and 7 mm) with traps installed at 1.16 m from the ground (Experiment 1), heights of installation of the traps (0.00, 0.40, 0.80, 1.20, 1.60 and 2.00 m from the ground) (Experiment 2) and bottle colors (yellow, blue, white, green, red and transparent) (Experiment 3). The collected data were subjected to Tukey’s test (p < 0.05). The ideal traps for collecting C. hominivorax in the field were those with opening diameter of 6 mm, height installation of 1.20 m from the ground, using transparent PET bottles.

Application of a putative alarm cue hastens the arrival of invasive sea lamprey (Petromyzon marinus) at a trapping location

The sea lamprey Petromyzon marinus is an invasive pest in the Laurentian Great Lakes basin, threatening the persistence of important commercial and recreational fisheries. There is substantial interest in developing effective trapping practices via the application of behavior-modifying semiochemicals (odors). Here we report on the effectiveness of utilizing repellent and attractant odors in a push–pull configuration, commonly employed to tackle invertebrate pests, to improve trapping efficacy at permanent barriers to sea lamprey migration. When a half-stream channel was activated by a naturally derived repellent odor (a putative alarm cue), we found that sea lamprey located a trap entrance significantly faster than when no odor was present as a result of their redistribution within the stream. The presence of a partial sex pheromone, acting as an attractant within the trap, was not found to further decrease the time to when sea lamprey located a trap entrance relative to when the alarm cue alone was applied. Neither the application of alarm cue singly nor alarm cue and partial sex pheromone in combination was found to improve the numbers of sea lamprey captured in the trap versus when no odor was present — likely because nominal capture rate during control trials was unusually high during the study period. Behavioural guidance using these odors has the potential to both improve control of invasive non-native sea lamprey in the Great Lakes as well as improving the efficiency of fish passage devices used in the restoration of threatened lamprey species elsewhere.

Ultra-fast underwater suction traps

Carnivorous aquatic Utricularia species catch small prey animals using millimetre-sized underwater suction traps, which have fascinated scientists since Darwin's early work on carnivorous plants. Suction takes place after mechanical triggering and is owing to a release of stored elastic energy in the trap body accompanied by a very fast opening and closing of a trapdoor, which otherwise closes the trap entrance watertight. The exceptional trapping speed—far above human visual perception—impeded profound investigations until now. Using high-speed video imaging and special microscopy techniques, we obtained fully time-resolved recordings of the door movement. We found that this unique trapping mechanism conducts suction in less than a millisecond and therefore ranks among the fastest plant movements known. Fluid acceleration reaches very high values, leaving little chance for prey animals to escape. We discovered that the door deformation is morphologically predetermined, and actually performs a buckling/unbuckling process, including a complete trapdoor curvature inversion. This process, which we predict using dynamical simulations and simple theoretical models, is highly reproducible: the traps are autonomously repetitive as they fire spontaneously after 5–20 h and reset actively to their ready-to-catch condition.

Modified Lobster Traps for Catching Crabs and Keeping Lobsters Out

Before redesigning lobster traps for capturing crabs and excluding lobsters, laboratory tests were done to determine the ability of both crabs Cancer irroratus and lobsters Homarus americanus to pass through simulated trap entrances and escape holes of various sizes and shapes. A long rectangular opening 44.5 mm (1.75 inches) wide allowed most crabs to enter, yet prevented passage of most legal-size lobsters. For use as escape holes in traps, round openings were found to be more effective than square ones to allow escape of lobsters while retaining commercial-size crabs.Lobster traps were then modified by closing the fishing heads and providing a long rectangular entrance at the top of the trap. Trap entrance widths of 44.5 and 51 mm (1.75 and 2.0 inches) fished crabs equally well; traps with a 38-mm (1.5-inch) entrance, and unmodified lobster traps caught fewer crabs. No lobsters were caught in the modified traps with entrance at the top.