Day (9,10,11): eight large black carabids, one large blueish carabid (Leistus spinibarbis – see below), two Bembidion-looking carabids (Bembidion tetracolum, possibly), three staphylinids. One more unidentified small black beetle. Fly larvae hatched and very active on the bait.
Day (12,13,14): six large carabids (largest ~17mm), two smaller Notiophilus-looking carabids, one small staphylinid, one larger staphylinid (~9mm). Another one of those little black beetles.
Days 15-21 (total): two small staphylinids, one larger staphylinid, one carabid, another of those little black beetles (maybe some kind of nitidulid?).
While more insects were caught in the second week than in the first, very few were caught in the third week. This could be a result of the increasing attractiveness of the trap to predatory and carrion-associated insects as time progressed, followed by a period of temperatures low enough to inhibit insect activity.
- The box protected the trap and bait very effectively. However, it is possible that it trapped the VOCs associated with decomposition rather than allowing them to spread, meaning that fewer insects were attracted to the trap. Holes in the side of the box, allowing air to pass through it, would eliminate this concern.
- The bottle trap caught a great number of flies – possibly due to the fact that it contained a small amount of the bait. Being unable to escape from the trap themselves, and difficult to encourage to leave the food source inside it, flies soon overpopulated the trap. In future, no bait will be placed in the bottle trap and the flies caught in it will be collected regularly.
- The pitfall trap was subject to the usual pitfall trap annoyances – difficult digging a deep enough hole, soil falling into the trap, difficulty ensuring the top of the trap was flat with the soil, and collapse of the hole when removing the pitfall trap to collect captured insects. A slightly more complex trap might remove these annoyances.
Pitfall trap 2.0:
Requires two identical pots (e.g. yoghurt pots).
The first pot is placed in the ground as normal, level with the soil. A centimetre or so of the top of the second pot is removed, and then the second pot is placed within the first. The second pot will be able to be removed without risk of damaging the hole, and replaced without requiring re-leveling of the soil.
- Both traps were non-lethal. Since several of the insects collected were predatory, it is very possible that more insects were captured than were collected. A lethal trap has its own pros and cons, but could give a more complete picture of the local insect community.
- It is questionable whether the bait specifically attracted any particular insects, since all of the insects caught were fairly ubiquitous. Bait may not be necessary for future projects – or, alternatively, different baits may be tested to see which are the most effective.
- I was unable to check the trap daily. This may have resulted in the loss of specimens. Checking traps daily in future is likely to be beneficial.
- The cold weather is probably responsible for the decrease in the number of insects captured. Projects undertaken in warmer weather may yield better results.
- Most specimens captured in the pitfall trap were released shortly after collection. Keeping specimens would have allowed easier identification. Which leads me to…
- Identification to species level. The aim of this project was to identify captured insects to family level. A future project could use lethal traps (or non-lethal traps, followed by collection and freezing of interesting specimens) to collect insects and aim to identify them to species level in the lab.
If anyone’s interested, I’ve found this site to be a really useful resource for beetle identification: http://www.thewcg.org.uk/