Low-Cost Automated Flight Intercept Trap for the Temporal Sub-Sampling of Flying Insects Attracted to Artificial Light at Night

1. Trap construction

NOTE: All of the components required to build the traps can be found in the Table of Materials. Each trap was constructed as shown in Figure 1 and Figure 2 by one person within 2 h.

1. Use a jigsaw to cut the polycarbonate roofing sheets (8 mm x 610 mm x 2400 mm) into 610 mm x 230 mm sections (Figure 1, item 1 & 2). Then cut a 8 mm center groove halfway up the center of each (610 mm x 230 mm) pane to allow the two panes to slide together to form a cross baffle.
2. Slide the crossed baffles snuggly into the plastic funnel opening (Figure 1, item 4) and secure them to the funnel with 20 mm stainless steel angle brackets (Fig 1, item 5b).
3. With the angle bracket in place, pre-drill holes and then use M4 screws and nuts with washers (Figure 1, item 6b) to secure the cross baffles to the funnel.
4. Again using the jigsaw, cut a piece of the polycarbonate sheeting (230 mm x 305 mm) from remaining sheets and secure with 20 mm stainless steel angle brackets (Figure 1, item 5a) at a 90° angle to the top of the crossed baffles to form a protective roof (Figure 1, item 3).
5. With the angle bracket in place, pre-drill holes and then use M4 screws and nuts with washers (Figure 1, item 6a) to secure the roof to the baffle.
6. Trim the funnel spout to a length of ~30 mm with a hacksaw to ensure the sample trays of the automated pet feeder will rotate unobstructed at the programmed intervals.
7. Place the automated pet dispenser (Figure 1, item 8) within a 9 L (38 mm diameter) plastic basin (Figure 1, item 7) to protect the samples from weather conditions.
8. Drill a 20 mm hole into the top of the 9 L basin and place the funnel spout into the hole to position it directly above the sample tray.
9. Using a drill with a hex-head driver bit, secure the plastic basin covering the pet feeder to a 500 mm piece of treated pine fence paling (Figure 1, item 9) with galvanized hex-head screws (Figure 1, item 14).
10. To stabilize the entire trap for hoisting into the air via ropes, attach a wooden stake (17 x 17 x 1200 mm, Figure 1, item 10) to the piece of treated pine fence paling (Figure 1, item 9) with an angle bracket and tie wire (Figure 1, items 13, 15 and 16).

Figure 1: Schematic diagram of trap construction. (1 and 2) 610 mm x 230 mm x 8 mm polycarbonate sheets; (3) 230 mm x 305 mm x 8 mm polycarbonate sheet; (4) 24 cm diameter plastic funnel; (5a–b) 20 mm angle brackets; (6a–b) M4 x 15 mm screws, washers & nuts; (7) 38 cm diameter 9 L plastic basin; (8) automated pet food dispenser; (9) 150 mm x 12 mm treated pine paling; (10) 17 mm x 17 mm x 1200 mm wooden stake; (11) 125 mm x 150 mm angle bracket; (12) 16 mm x 16 mm hex-head screws; (13) angle bracket; (14) 16 mm x 16 mm hex-head screws; (15 and 16) wire stabilizer; (17) karabiner, used for lowering and raising into position. Please click here to view a larger version of this figure.

2. Trap deployment

NOTE: The traps were attached to trees 6 m above the ground (directly below the experimental or control lights) to capture flying insects (Figure 2). Emptying and collection of traps were done by three people on a single day. Further days can be sampled if required by lowering the trap to remove the collected samples, resetting the pet food dispensers, and placing the trap back in position every three days based on the sampling regime.

Figure 2: Low-cost automated flight intercept trap for sampling insects at user-defined time points. (A) Polycarbonate crossed baffles serve as the flight intercept area that allows for collecting insects from all four sides. The polycarbonate roof serves to direct insects downwards and protect the collected samples from the weather. The funnel beneath the flight intercept barrier servers to funnel insects that have collided with the polycarbonate barriers into the collecting trays housed within the circular basin. (B) Trap suspended below experimental light and secured to the tree by a wooden stake and angle bracket. The plywood box below the intercept trap contains a bat detector used to passively record echolocation calls produced by free-ranging insectivorous bats. Please click here to view a larger version of this figure.

1. Once at the sampling location, remove the automated pet food dispenser (Figure 1, item 8) from beneath the plastic basin.
2. Open up the automated pet food dispenser (Figure 3A) and place foil dishes containing soapy water or a preservative of choice in each food tray (Figure 3B, here 20 mL of propylene glycol was used as a preservative).
3. Follow the directions provided with the automated pet food dispenser to set the food tray rotation times. First, set the clock time, then program each pet food dispenser tray.
   ​NOTE: The automated pet food dispenser rotates food trays (1-6) at pre-programmed times. The 6-meal bowls can be set to open at any time of the day or night, with the trays rotating in sequential order. For this study, the aim was to sample nocturnal and diurnal insects separately. Tray 1 sampled from 8 PM on the first night and then moved to tray 2 at 7 AM the following morning, followed by tray 3 at 8 PM, tray 4 at 7 AM, tray 5 at 8 PM and tray 6 at 7 AM. A delay function allowed for a one-day delay in sampling because it took 2 days to set up all sites, thereby ensuring sampling commenced on the same day/time at all sites.

Figure 3: Automated pet food bowl. (A) Battery-operated 6-meal pet food bowl used to sample insects at user-defined intervals. The food bowls were programmed on alternating schedules to sample nocturnal and diurnal insects. For example, tray 1 opened at 8 PM (nocturnal day 1), tray 2 opened at 7 AM (diurnal day 1), tray 3 opened at 8 PM (nocturnal day 2), tray 4 opened at 7 AM (diurnal day 2), tray 5 opened at 8 PM (nocturnal day 3), and tray 6 opened at 7 AM (diurnal day 3). (B) Lid removed from automated pet food bowl to show the six collection trays. Foil dishes containing propylene glycol as a preservative allowed for the easy removal of the collected insects. Please click here to view a larger version of this figure.

4. Place the automated pet food dispenser back underneath the plastic basin and secure the basin to the timber fence piece with the galvanized hex-head screws (Figure 1, item 14).
5. Attach a rope to the top of the trap with a karabiner (Figure 1, item 17). With the use of a ladder, hoist the trap into position and secure it beneath experimental lights by the karabiner.
6. Attach a second wooden stake (17 mm x 17 mm x 1200 mm, Figure 2B) to the tree (or lamp post) with an angle bracket to stabilize the trap in high winds.
7. The trap sits on top of the stake; secure it with two large cable ties (Figure 2B).
8. To collect insect samples, lower the traps with a rope. Remove the automated pet food dispenser from beneath the plastic basin.
9. Remove the lid of the pet food dispenser (Figure 3A) and lift the aluminum trays out to pour the contents into pre-labeled sample vials (Figure 3B).