Collectors

Ideal Collector 37k

Suspension systems are best for traps like the Nzi. There are many simple and economical options.

Practical details are provided for two situations typical of large catches in the Tropics, or small catches in the North. Use common sense to adapt these ideas to local conditions and materials.

For more detailed examples and technical discussion, see Systems for Collectors.

The system above has been used for many years for catches of tsetse and other biting flies (e.g. thousands per day) in Africa. It uses an initial exit from the cone consisting of a short funnel with an appropriate exit hole size (e.g. top of a 1.5 litre plastic water bottle). The funnel is used as a point of attachment for thin wires suspended from a flexible pole. This lifts and spreads the cone without putting too much tension on any single point. Another plastic bottle provides an intermediate chamber through which flies eventually find their way to the ultimate collecting chamber, a very large plastic bag. Any similar combination of bottles and plastic or mesh bags can be used to provide a stable collecting system that is easy to maintain. Systems like this can be left in place for long periods (e.g. a month) as the flies simply die from heat exposure, desiccate and accumulate in the bag.

Tabanus quinquevittatus
crawling in bottle collector

Flies crawl and fly about within collectors and can sometimes find their way back into the trap cone, and from there, escape out of the trap body. Hence, an important feature for any system is the creation of a large, transparent space away from the route back into the trap at the apex of the cone.

In the absence of any information on fly behaviour, the exit from the trap cone should be smaller rather than larger (e.g. roughly an inch or 20 - 25 mm may be best).

Other Traditional Collectors from Africa

Wire Frame Cage 21k

Vavoua Trap
Kenya 1993

For small catches in traps that are set with a central support pole (e.g. the biconical trap), researchers often use a wire cage (20 x 10 x 7 cm) with a long netting sleeve.

The sleeve is fastened with a thin wire to a special pyramidal or conical frame inserted into a central support (e.g. a hollow metal plumbing pipe). The frame spreads the cone and has a small hole of suitable size at the top (e.g. 10 x 20 mm is used in West Africa).

Here, a catch of 3,000 stable flies in one day in a Vavoua trap set in Nairobi National Park in Kenya is obviously too high for this type of collector.

Epsilon Cage 23k

Epsilon Trap
Zimbabwe 1997

A similar option for a trap suspended from above is the use of a netting sleeve and a wire frame around the top of a plastic bottle set into a ring at the apex of the cone.

This vertical arrangement is only suitable for short-term collections where flies remain alive and are not likely to die and accumulate at the base of the sleeve. For example, This option was used by John Hargrove for late afternoon collections with Nzi and Epsilon traps.

A compendium of considerable practical information is available at the Natural Resources Institute, United Kingdom

Bait Technologies