INVERTEBRATE CAPTURE TECHNIQUES

CHAPTER 4

Trapping Methods:

 - Light Traps:

Many insects and other invertebrates have a reaction to light and this has often been satirised in various newspapers when certain politicians are attracted to unethical procedures "like moths to a flame". However, the truth is very far from being as simple as it seems. Even now, after many decades of research, the real reason why so many insects and especially particular families of insect (e.g. moths), are attracted to light is not fully understood. The theories propounded have included the idea that moths migrate by using the moon and stars as navigational aids and that the placement of a light on the ground causes subtended angles of  light at the insects eye to alter so rapidly that it flies in a spiral to reduce the angular change - this resulting in the insect flying into the trap. However, there is much work to be done in this area before the actual mechanism of attraction and/or repulsion is understood and why the degree of attraction or repulsion differs with different insect species, families and orders.

  - Open Bulb Trap:
 

  - MV with Sheet:
 

  - MV with Trap:
 

   - Robinson Trap:
 

   - Skinner Trap:
 

   - Night-time:

      - Moths, Lacewings, Parasitic Hymenoptera, Dung-beetles, Bugs, Lesser earwigs, etc.

   - Day-time:

       - beetles from compost-heaps
 

  - Aerial Light-trapping:
 

  - Actinic Traps:

     - Portables:

     - Heath, ????
 

  - Tungsten:

     - Rothamsted:

     - live and/or poisoned
 

  - Underwater Light Traps:

     - Caddis, Beetles, Boatmen, etc.
 

 - Pitfall Trapping:
 
    - empty traps:

    - preservative traps:

    - baited traps:
      - meat:
      - fish:
      - fruit:
      - chemical (e.g. ammonia):

 - Manitoba Trap:

 - Malaise Trap:

The Malaise Trap is used mainly for the capture of flying insects, especially flies, wasps, and bees.

It is composed of a large tent built of netting, approximately 4 to 6 feet in height and 3 to 5 feet in width. The side walls of a conventional tent are removed and a central wall running through the middle of the tent is put in place. The roof of the tent slopes, along the ridge, from the front of the tent to the rear and a small entrance to a killing bottle is provided at the top most part of the roof.

How does it work? The answer is very simple. The insects fly into the central wall of the tent by which time they are under the main roof. They then fly upwards trying to escape from the obstruction whereupon they encounter the sloped ridge of the roof. Again, they move up the slope of the ridge until they encounter the entrance to the killing jar and that is the final receptacle. Malaise traps work exceptionally well for Diptera (Flies), and Hymenoptera (Wasps and Bees). Occasional specimens of moths, butterflies, and beetles will be taken. It has been suggested that a smaller version standing only 2 feet high may prove useful for micro-lepidoptera (micro moths) though this has yet to be proven.

  - Aerial Malaise Trapping:

 A form of Malaise Trap with a netting base and a rigid roof ridge pole may be hoisted up into the eaves of tall-buildings or the canopies of trees to trap high flying migrant insects or to sample the fauna associated with such specific habitat niches.

 - Interception Net Trapping:

This is a very simple form of netting trap which has only recently begun to find favour in Britain despite its use in America, Canada and the tropics for a great many years. It appears to be useful for catching a range of beetle species which are not normally found by more 'normal' sweep-netting or habitat searching techniques. Traps of this general design have also been used to trap Hymenoptera (Bees and Wasps).

The trap consists of a netting screen approximately 6 feet long by 3 feet high and may be fitted with a rain-deflecting roof - this 'extra' is particularly useful in Britain with its rainy climate , especially if the trap is to be left for a few days or more. The netting should preferably be black Dacron or Terylene and should not be a material which would allow an insect a foothold. The rectangle of net should be bound around its edges with tape and loops attached at the sides through which two supporting poles may be passed. The net should be set up vertically with the poles supported by guy ropes and the whole structure should be taut in order to both present the least chance of a foothold to obstructed insects and also to produce the minimum of movement should a wind or breeze arise.

A row of aluminium food containers of the sort normally associated with take-away Chinese food should be placed under the lower edge of the net. If the trap(s) can be inspected daily then this is all that is necessary, however, if the trap must be left for a day or so then there is a need to place a preservative in the containers in order to prevent losses due to carnivores or to rotting due to dampness. This should be composed of either water with a few drops of detergent added if the trap can be visited every couple of days or an ethylene glycol based car-antifreeze if the gaps between visits is likely to be longer than 2 days.

These traps are very noticeable and should therefore be set up away from the public gaze in order to reduce vandalism. They should be sited across a woodland ride or at 90° to a woodland or forest edge or in some natural corridor but preferably where they will not be visited by deer, horses, cattle or other large mammals.

  - Aerial Interception Net Trapping:

  A form of interception net trap has been devised for the trapping of beetles in the canopies of trees. This net is composed of two small panels of net approximately four feet square set at right angles to each other to form a cross. A sloped net roof is constructed, and the lower part has a polythene catching funnel made which leads down to a killing jar half-filled with ethylene glycol. The beetles fly into one of the net covered arms of the cross, drop into the polythene funnel and slide down into the killing jar.

 - Pheromone Trapping:
    - Moths, Micro-moths, Pest Species, Cockroaches

 - Log and Dead Wood Emergence Traps:

 - Leaf-Miner Emergence Traps:
    - Micro-moths:
    - Diptera:
    - Beetles:
    - Parasitic Hymenoptera:
    - Parasitic Diptera:

 - Tree Belts:
    - Corrugated Cardboard:
    - Bubble Plastic:
    - Hessian & Peat:
    - Spiders:
    - Lacewings:
    - Lepidoptera Pupation Sites:

 - Floating Bottle Traps:

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