Like Moths around a Flame

Wednesday, June 15, 2011
Steve Goddard

Insect trap

Several days ago I came across two primate specialists in the forest. One was wearing a loudspeaker on her head that was emitting monkey calls (calls of the saddle-backed tamarin, I believe). This got me to thinking about the ways we stretch to get our data, to study animal and plant behavior, to collect specimens, and to document the comings and goings of species. It's hard work that demands a staggering array of equipment from a butterfly net to a portable mass spectrometer. It also requires smart, fit, capable, adaptable people with highly specialized training and lots of imagination. Everyone who contributes to the community at the CICRA field station shares these characteristics — the permanent staff, the visiting researchers and the students. The sense that just being here is fragile and very special engenders a work ethic in which nothing is wasted; not time, not materials, and not effort. Need ethanol to store you specimens in? It will come over the Andes by truck, then by small boat up the Rio Madre de Dios to be carried by hand up the near vertical ascent from the riverbank to CICRA.

So, back to the loudspeaker-on-the-head thought — what do the specialists working with our K.U. entomology team use to trap and study insects? I've been keeping track:

insect trap

Malaise Trap

This is a mesh trap that insects fly into. Once they have hit the mesh they tend to cling onto it and start to climb – ultimately into a trap. The traps are often jars or pans of water with a little detergent in them to break the surface tension. There are two variations on this theme:

The Terrestrial Malaise trap sits on the ground

The Canopy Malaise Trap is like a rigid tent that gets raised 20-30 meters up into the forest canopy. It also has a trap to collect insects that that don't grab the mesh but fall after hitting it.

Flight intercept trap

This is similar to a terrestrial malaise trap but it has only a vertical mesh, stretched taught, with pans underneath it to catch flying insects that crash into it and fall

Pan Trap

Another terrestrial trap is the pan trap -- little dishes of water and detergent that are set on the ground or, in the case of the pitfall trap, set into the ground so the lip is level with the ground. The K.U. team uses yellow and blue plastic ware dishes as some insects prefer these colors. Gardeners will recognize the pitfall trap because it is nearly identical to the standard trap for slugs: a container of beer set into the ground with the lip of the container level with the ground.

Chemical Lure Trap

These are just what they sound like: traps that rely on an insect's interest in certain smells. These need not be fancy pheromones; Reed Niemack of our group has been testing eucalyptus oil, methyl salicylate (wintergreen), vanilla, and Listerine to attract orchid bees. The trap consists of a length of clothesline dipped in one the above solutions and suspended from a branch. The researcher passes by the traps after a set period of time and collects any orchid bees to be had. Eucalyptus oil and wintergreen seem to be the big winners. [photo shows a bumble bee attracted to wintergreen]

Light Traps

Two varieties of light trap have been used by the K.U. team on this research trip — all depend on the “moths around a flame” principle: Ultraviolet Light Trap - this is sheet draped over a rope with an ultraviolet light shining on it. This attracts all kinds of insects, including (one night) a large rhinoceros beetle.

CDC light trap These light traps use a narrow UV spectrum and are designed especially for for mosquitoes

Multilure traps

These generally use some combination of scent, bait and light to capture insects, especially flies.

Mouth Aspirator, aka "pooter"

This device is essentially a collecting jar with a long rubber tube and a short metal tube coming out of it. One sucks on the rubber tube while aiming the metal tube at a small insect to vacuum it into the bottle. This device was used by Tom Radocy of our group in order to sample the mosquito populations at the CICRA field station (happy birthday, Tom!) [photo courtesy of Jeff Miller]

Hand Methods

I suppose there is no end of what these might include. On this trip I have seen our team wield the butterfly net, the sweep net, use their cupped hands, and tap insects into small bottles, baggies etc.

I wonder what techniques are used to trap the mass-marketed insect displays from Amazonia that are available in the shops in Lima; and I wonder if the distinction between specimen and trophy has been lost?