| An optical sensor that was designed to remotely detect flying insects (OFIDIS; www.qubitsystems.com) was evaluated outdoors under full sunlight. Shadows cast by an artificial insect (an electric toothbrush oscillating at 53 Hz over a 120° angle), were detectable up to 35 m away from the sensor: they weakened with distance at a rate of y = 902e-0.11x (r2 = 0.9 at p < 0.001). Shadowed signals were undetectable when sunlight intensity was reduced below 20,000 lux. Sunlight signals reflected from a mirror attached to the oscillating toothbrush remained detectable and strong (y = -0.24x + 86; r2 = 0.33) beyond 25 m. The ability of this sensor to detect differences in abundance, as well as density in flying insect populations, was evaluated in three replicated site types: old-field, wetland, and parking lot. Insect signal abundance (based on differing fundamental wing-beat frequencies of each signal) at both old-field and wetland locations were higher than that of the parking lot and control (F = 8.85; df = 8; P > 0.0001). Signal richness was greatest in the old-field (R = 259) and least rich in the parking lot (R = 88). However, diversity was greatest at the wetland (H' = 2.26; H' max = 2.7), showing a high richness that was most evenly distributed from 100--1000 Hz. Combined with an appropriate data logger, this year 2000 sensor is a promising development for remote sensing of insects with wing-beat frequencies over 100 Hz, notably Diptera and Hymenoptera. |
