Low-Cost Automated Flight Intercept Trap for the Temporal Sub-Sampling of Flying Insects Attracted to Artificial Light at Night
Summary
To study the impacts of artificial light at night (ALAN) on nocturnal flying insects, sampling needs to be confined to nighttime. The protocol describes a low-cost automated flight intercept trap that allows researchers to sample at user-defined periods with increased replication.
Abstract
Sampling methods are selected depending on the targeted species or the spatial and temporal requirements of the study. However, most methods for passive sampling of flying insects have a poor temporal resolution because it is time-consuming, costly and/or logistically difficult to perform. Effective sampling of flying insects attracted to artificial light at night (ALAN) requires sampling at user-defined time points (nighttime only) across well-replicated sites resulting in major time and labor-intensive survey effort or expensive automated technologies. Described here is a low-cost automated intercept trap that requires no specialist equipment or skills to construct and operate, making it a viable option for studies that require temporal sub-sampling across multiple sites. The trap can be used to address a wide range of other ecological questions that require a greater temporal and spatial scale than is feasible with previous trap technology.
Introduction
There are many arthropod sampling techniques1,2,3, but ecologists often have difficulty applying these methods in ways that are appropriate to their research questions (see4). When choosing an appropriate method for sampling insects, ecologists must consider the targeted species, time, effort, and cost involved in different techniques. For example, a common limitation is that it can be logistically challenging to sub-sample during specific time periods over replicated sites to quantify temporal variables which influence species activity, such as changes in weather or circadian activity (but see5). Most passive-survey insect traps are set for long periods (e.g., over multiple days, weeks, or even months), lacking fine-scale temporal resolution1. For surveys targeting specific time periods across multiple replicate sites (such as nocturnal sampling only across distinct sites), a large team may be required to visit sites over multiple days at the same time points (e.g., within 30 min of sunrise and sunset) to collect specimens and reset traps6; otherwise, an automated trapping device is required5,7,8.
There is a growing field of work on the impacts of artificial light at night (ALAN) on insect activity patterns and localized population dynamics9,10; and on the interactions between ALAN and rates of insect predation4,11,12,13. However, to study the impacts of ALAN on nocturnal insect taxa, sampling needs to be confined to nighttime. Several different active light traps have been described and used for automated temporal sampling of nocturnal insects14. Some examples include simple falling disk-type separation devices, where the catch falls into a narrow tube with a disk falling every hour to separate the catch15, or turn-table separation devices that rotate collection bottles at timed intervals7,16,17. These previous automated light traps address the sampling challenges involved with temporal survey requirements but are often large and unwieldy and use outdated or unreliable technology. A new automated passive sampling device was recently developed and tested8. This device utilized a commercially available flight-interception trap paired with a lightweight custom-designed collection device consisting of a turn-table holding sampling cup that allows for collecting trap contents at user-defined intervals8. This new automated trap employs sophisticated programming that can be operated by a smartphone but is prohibitively expensive to build at around EURO 700 (AUD 1,000) per trap8.
Flight intercept traps are one of the most efficient ways to survey flying insects1,18,19 and work on the principle that flying insects fall to the ground when they collide with a vertical surface. Flight intercept traps come in a variety of designs. However, most are typically constructed with a transparent or mesh surface and a collecting container filled with water and/or a preservative. The new trap described here uses a cross vane/baffle type or multidirectional intercept trap20, given that cross baffles have been shown to increase capture rates14,21 and sample insects from all directions. The purpose of this trap is to survey nocturnal flying insects that are attracted to artificial lights. This phototaxis results in insects circling the light source22; hence a multidirectional trap is most suitable.
Described here is a low-cost automated intercept trap that requires no specialist equipment or skills to construct and operate. The trap uses a commercially available automated pet food dispenser and common items available from hardware stores. This design costs less than EURO 66 (AUD 105) per trap to construct (Table 1), making them a viable option for studies requiring temporal sub-sampling across multiple sites simultaneously.
Protocol
Representative Results
Discussion
Despite the automated flight-intercept trap described by Bolliger et al. (2020)8 being well designed and very effective at sampling at user-defined time periods, they are likely to be cost-prohibitive for many researchers. This study shows that passive trapping surveys using automated traps for sub-sampling flying insects at user-defined periods can be carried out on a modest budget. Traps were built to sample at six pre-defined time points by utilizing a commercial pet food dispenser and material…
Divulgazioni
The authors have nothing to disclose.
Acknowledgements
The research was funded through the La Trobe University Net Zero Fund, sponsored by Sonepar. The research was conducted under Department of Environment, Land, Water and Planning scientific permit no. 10009741. We thank Martin Steinbauer for comments on an early draft and two anonymous reviewers.
Materials
| Batteries (C cell) – 10 pack | Duracell | MN1400B10 | https://www.duracell.com.au/product/alkaline-c-batteries/ |
| Battery operated automated 6 meal pet food bowl – each | OEM China | XR-P006-002 | Automated 6-meal pet food bowls range in price dependent on supplier, for example in the UK they can be purchased for £19 GBP ($36 AUD). |
| Galvanised hex-head screws (10-16 x 16 mm) – 100 pack | Bunnings Warehouse | 1-311-9151-CTPME | Bunnings Warehouse is an Australian hardware chain with stores in Australia and New Zealand. Items purchased from Bunnings Warehouse can be found at most hardware stores. https://www.bunnings.com.au/ |
| Galvanised steel angle bracket (125 x 150 mm) – each | Bunnings Warehouse | AZ11 | https://www.bunnings.com.au/ |
| Galvanised tie wire (0.70 mm x 75 m) – per roll | Bunnings Warehouse | 50218 | https://www.bunnings.com.au/ |
| Plastic basin (38 cm, 9 L round) – each | Ezy Storage | FBA31541 | https://www.ezystorage.com/product/laundry/basic-accessories/9l-round-basin/ |
| Plastic funnel (24 cm) – each | Sandleford | Pf24 | https://www.sandleford.com.au/plastic-funnel-24cm |
| Stainless steel angle bracket (20 mm) – 16 pack | Bunnings Warehouse | WEB2020 | https://www.bunnings.com.au/ |
| Stainless steel screws & nuts (M4 x 15 mm) – 18 pack | Bunnings Warehouse | SFA394 | https://www.bunnings.com.au/ |
| Stainless steel washers (3/16” & M5) – 50 pack | Bunnings Warehouse | EBM5005 | https://www.bunnings.com.au/ |
| Sunlite Polycarbonate roofing sheet (8mm x 610 mm x 2.4 m) – each | Suntuf (Palram Industries Ltd) | SL8CL2.4 | https://www.palram.com/au/product/sunlite-polycarbonate-multi-wall/ |
| Treated pine paling (150 x 12 mm) – each | STS Timber Wholesale P/L | n/a | https://www.ststimber.com.au/sts-timber-wholesale-products/fencing |
| Wooden stakes (1200 x 17 x 17 mm) – 10 pack | Lattice Makers | n/a | https://latticemakers.com/product/tomato-stakes-17x17mm-pack-of-10/ |
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