Ground bottle traps
Ground bottle traps were designed as an easier-handling alternative to the Spurr wasp traps for generalised sampling, but work on a similar principle. The basic unit consists of a standard 3 litre plastic juice bottle (the rectangular ones) with the base cut off and six 20-mm-diameter entrance holes drilled around the sides. The bottle is placed on the ground over a small bait container and is held firmly in place by two high tensile wire pegs inserted through small holes on opposing corners of the bottle where the neck begins to narrow down. The bait container should have a large hole covered with insect screen to allow the scent of the bait out, but to prevent access to the bait by insects. A small Malaise-type collecting unit is connected to the threaded neck of the main bottle by a 45° angle joiner for a 32-mm pressure pipe. The smell of the bait attracts the insects to go into the main bottle, and after investigating the bait container they instinctively move upwards to get out. This quickly leads them into the collecting bottle where they are caught in a suitable preservative.
As with the Spurr wasp trap, the type and abundance of insects collected varies with the bait used. We used a solution of fermenting brown sugar and found this to be attractive to many things, including social bees and wasps, ants, grasshoppers, beetles blow flies, vinegar flies, and surprising numbers of mosquitoes.
Retrieving the sample from these traps is simply a matter of unscrewing the collecting jar. Refreshing the bait is also easy and most of the insects do not get caught in it, although we found that if the mesh size on the bait container was too large, ants got in. In testing the ground bottle traps with hanging Spurr wasp traps with the same bait at the same time, we found the ground traps collected significantly more flies, beetles, and bugs, but significantly fewer ants.