Warren Chinn, our resident bug man, has been out and about, day and night, sampling invertebrates on many of the tiny islands, and also on the much larger Raoul Island. As it is such a big island he has just spent three days and two nights ashore there, trying to cover lots of ground with different types of habitat. His main method of collecting is to use a sweep net, which he swooshes back and forth through vegetation as he passes to dislodge critters into the net.
Bug man: Warren “swooshes” his sweep net in the hunt for new species on Raoul
If Warren is an area for a few hours he suspends an insect trap, called a malaise trap, from a tree. This is a very simple device that relies on basic insect behaviour to make a catch. The bottom part of the trap is a black net, which is effectively an invisible barrier to flying insects such as flies. The flies fly into the black net and then begin to crawl for the brightest part of the ‘sky’ they can find – which in this case is the white top half of the net. They crawl up, and into the whitest part of the net, which is a plastic white jar.
Another tool of the bug trade – the malaise trap
The jar has an inverted moat on the inside which is filled with alcohol, and the design of the trap essentially guides the insects into the moat. Warren can simple take the trap down, and pour any insects he collected into a small sampling jar for later sorting. Here is the haul from the malaise trap this morning – lots of flies, and a few moths.
Bugs in a jar: the latest haul from the malaise trap – lots of flies and a few moths
One of the main features of both Raoul and the smaller islands are the ants, especially large-headed ants, many of which are introduced. I asked Warren to sum up the invertebrate fauna of the islands and he said ‘lots of a few things’. So, not a great diversity of species, but the ones that are present are often quite numerous, and often small.
Although Raoul is now free of introduced mammals (two species of rats were eradicated in 2002) they almost certainly decimated any large insects such as weta and beetles that might have once been here.
