Monitoring Mosquito Abundance: Comparing an Optical Sensor with a Trapping Method

Abstract

Optical sensors have shown significant promise in offering additional data to track insect populations. This article presents a comparative study between abundance measurements obtained from a novel near-infrared optical sensor and physical traps. The optical instrument, named an Entomological Bistatic Optical Sensor System, or eBoss, is a non-destructive sensor operating in the near-infrared spectral range and designed to continuously monitor the population of flying insects. The research compares the mosquito aerial density (#/m³) obtained through the eBoss with trap counts from eight physical traps during an eight-month field study. The eBoss recorded over 302,000 insect sightings and assessed the aerial density of all airborne insects as well as male and female mosquitoes specifically with a resolution of one minute. This capability allows for monitoring population trends throughout the season as well as daily activity peaks. The results affirmed the correlation between the two methods. While optical instruments do not match traps in terms of taxonomic accuracy, the eBoss offered greater temporal resolution (one minute versus roughly three days) and statistical significance owing to its much larger sample size. These outcomes further indicate that entomological optical sensors can provide valuable complementary data to more common methods to monitor flying insect populations, such as mosquitoes or pollinators.

Keywords: culicidae; insect abundance; mosquitoes; optical sensors; population monitoring; trap; vector control.

Figure 1

Optical layout of the eBoss instrument.

Figure 2

(a) An example of an optical signal caused by a flying insect; (b) change in signal intensity due to the insect’s body (top) and wing (bottom) contribution. The optical extinction cross-section of the wings and body is derived from the drop in voltage $V_w$ and $V_B$, respectively.

Figure 3

(a) An example of an optical signal caused by a flying mosquito; (b) FFT analysis on the transit signal, showing harmonic peaks with first and fundamental peaks at around 500 Hz.

Figure 4

Location of physical traps (red markers) in Hudson County, NJ (red dotted line); the location of the eBoss instrument is indicated by the blue marker.

Figure 5

Distribution of different insect clusters showing aerial density; each bin is defined by optical extinction cross-section ratio and wingbeat frequency.

Figure 6

(a) Change in mosquito abundance throughout the entire season. (b) Mosquito aerial density as a date and time of the day; grey lines indicate sunrise and sunset times (EST, UTC-05:00).

Figure 7

(a) Mosquito abundance data from the physical trap (blue line) and eBoss instrument (red line); (b) a scatterplot showing the correlation between trap count per day and aerial density.

Figure 8

Top row: data collected by the eBoss and two light traps, the fitted within-year abundance trends, and two example simulations per device. Bottom row: The distributions of calculated proportional annual changes from pairs of simulations with the second simulation having a 5% increase added to the model (F’ is the normalized frequency density). The dotted vertical line shows the ‘true’ value of 0.05. The multiple curves for each device represent the combining of data from different numbers of devices.