(8) Yellow pan or Moericke trap
This is an excellent method of collecting chalcidoids, notably mymarids and encyrtids, as well as other groups of insects. Species that are rarely swept or collected in Malaise traps can often be collected using this technique. It relies on the fact that many insects associated with herbaceous vegetation are attracted to yellow. The trap consists of a shallow tray, about 60-75 mm deep and with an area of about 300-400sq cm. This is painted bright yellow on the inside. The tray is placed on the ground in a suitable habitat such as grassland, a forest trail or clearing, etc. It is filled with water (plus a drop or two of detergent to break the surface tension), saturated salt solution, or a 50/50 mix of ethylene glycol and water. If water only is used then the pan must be emptied at least once a day, otherwise specimens will become partly macerated, particularly in warm weather, Pans containing salt solution may be left a couple of days and those containing ethylene glycol/water mix can run for a week without being emptied.
To empty the trap it is easiest to use one of the types of net sold for cleaning domestic fish tanks. If this is run across the bottom of the pan most of the material will be disturbed enough to lift off the bottom and find its way into the net. Otherwise pour the contents of the pan through a piece of fine netting held in a 10-15cm diameter kitchen sieve. Using this method it is possible to service at least 100 traps in an hour with ease. Before transferring the specimens to alcohol it is essential to wash them thoroughly in clean, fresh water. This will prevent deposits forming on the specimens due to contamination from the detergent, salt or ethylene glycol.
Note. It has been found that correct siting of the trays is essential: even repositioning a tray by only 0.5-1m can increase the catch several times even where there is no obvious difference in the site chosen. Therefore it may be necessary to move the trays around until optimum sites are found.
Note. When microscope slides are to be made from the material, there is an increase in the antennae and/or head collapsing on final transfer to balsam (see below) if the specimens have been collected into ethylene glycol/water mix or salt solution. It is therefore best to use water/detergent as the collecting medium even though this means more frequent emptying of the trap.
Note. When a large number of traps are used at one time it is a good idea to number each trap in water-proof ink (eg "magic marker") on the floor of the tray to prevent overlooking traps when emptying them.
(9) Suction of vacuum sampler
A suction sampler is normally powered by a two-stroke motor that draws air through a length of tube about 5-30 cm in diameter. The open end of the tube is pushed into vegetation. Insects sucked in are trapped by a strong, fine net fitted across the inside of the tube within a few inches of the open end. The best method for sorting the catch is to transfer to the contents of the tube to a fine net bag for later examination using alight box or separation bag as described elsewhere. Another, more time-consuming method is dump the whole catch into alcohol or into a polythene bag and kill the insects by introducing a small piece of tissue soaked in ethyl acetate. The catch can then be sorted later under a stereo microscope (see "sorting material" elsewhere).
The suction sampler is ideal for sampling grassland, but may be used for sampling bushes, particularly those which are difficult to sweep, eg bushes with strong, sharp thorns. The main problem with this method is that most, if not all, of the larger species and also many of the smaller ones tend to escape. Other disadvantages of the suction sampler is that the apparatus is usually heavy and cumbersome to use and that only a limited sample can be taken at any given time. However, many otherwise rare species can be collected from grassy vegetation using this technique
(10) Suction trap
This is a reasonable method of collecting flying insects. The main disadvantage is that it needs an electric power source. The suction trap consists of a cylinder of 60cm diameter or so with a fine mesh gauze fitted inside. This leads into a collecting tube or chamber at the bottom containing saturated picric acid, water or alcohol. Air is drawn through the funnel by a fan. Passing insects are sucked down the gauze funnel and eventually fall into the collecting tube which must be emptied regularly. This type of trap is much less efficient than a Malaise trap and is less versatile than a yellow pan trap.
(11) Pitfall trap
This is a specialised method of collecting ground dwelling insects. In some areas the use of these traps can reveal chalcidoids that may otherwise be overlooked. It may be a suitable method of sampling in habitats where conventional method are not practical, eg in windy areas such as mountain tops. The pitfall trap consists of a jar or another suitable receptacle sunk in the ground and partly filled with saturated picric acid solution (see Note 4). This can be left for a week without servicing. The specimens collected in the pitfall trap must be washed thoroughly in clean water before transferring to 70% alcohol.Note. An advantage of using picric acid is that many specimens do not usually collapse very badly when dried in air. Unfortunately the gaster may become very distended in picric acid which may cause some taxonomic problems. Another disadvantage of using picric acid is that the dry crystals are highly explosive and the solution stains flesh very badly.
(12) Leaf litter or grass tussock sampling
In temperate regions many chalcidoids overwinter in leaf litter and grass tussocks. Specimens can be extracted by placing the litter/tussock in an emergence box or "Winkler" bag in a warm room. In many parts of he world, including the tropics a number of insects lay eggs on or near leaf litter and these may be subsequently parasitised by chalcidoids. These chalcidoids can be collected using the same techniques, but it may be necessary to keep the litter for up to three months before they emerge.
(13) Light trapping
This is perhaps one of the most overlooked methods for collecting chalcidoids. It is particularly efficient for collecting fig wasps in or near tropical forest habitats and also can collect species that are not known to fly at night, eg Copidosoma spp. (Encyrtidae).
Last updated 19-Aug-2003 Dr B R Pitkin