MALAISE/FLIGHT INTERCEPT SAMPLING PROTOCOLS
M.J. Sharkey
Eastern Cereal and Oilseed Research Centre, Agriculture
and Agri-Food Canada, Ottawa, Ontario, Canada K1A 0C6
The Malaise trap is constructed according to the
specifications of Townes (1972). In that article Townes
provides detailed measurements for construction of a Malaise
trap. Those measurements will not be repeated here.
Malaise traps catch flying insects. Most flying insects
that hit the central panel (Fig. 1) of the Malaise trap
respond by flying upward, presumably in an attempt to fly
over the barrier. The slanted roof directs insects toward the
high point of the trap and a bottle of alcohol into which
they are collected. There are two modifications that should
be applied to the Townes style trap. The first is a strip of
black material about 2 m long and 15 cm wide that is placed
along each edge of the roof of the trap. This acts as a
barrier to insects that try to fly out of the trap. The
result is that many more fast flying insects with good
eyesight are captured. The second modification is the size of
the mesh that is used. Instead of 10 meshes per cm as
suggested by Townes (1972), a mesh size of at least 24 per cm
has been shown to increase the diversity of the catch albeit
at the expense of some of the larger specimens with better
visual acumen.
Those insects that drop and those that fly down (e.g.
many Pompilidae) when encountering the central panel of the
Malaise trap are not sampled efficiently by Malaise traps. To
capture this component of the insect fauna a trough is placed
under the central panel of the trap. The trough runs the
length of the trap (about 2 m), is about 7 cm deep and 60 cm
wide. The trough is lined with thick, yellow vinyl that is
sealed at the corners. It can be filled with a variety of
fluids. Minimally the fluid consists of water saturate with
salt, and a small amount of detergent (20 ml) as a
surfactant. The trough should be flat and almost full so as
to maximize the time required for evaporation.
This combination trap now functions in four different
ways: 1) a Malaise trap to capture flying insects; 2) a
flight intercept trap to capture insects that drop when
encountering the central panel (mostly beetles); 3) a yellow
pan trap that attracts flying insects directly to the trough;
and 4) a pitfall trap if the trough is sunk to its depth in
the ground. Sinking the trough is not recommended if
surface-active fauna is to be analyzed separately from the
actively flying community.
Perturbations by large mammals (especially cattle) can
be a serious problem with Malaise traps. Avoid placement of
traps on or near game trails and construct exclosure fencing
for cattle if necessary. Fencing should be constructed of
materials that do not present a barrier to insect flight so
as not to cause insects to fly upwards over the fence and
over the trap.
It may be sufficient to place one of these traps in each
community sampled if species richness is the only parameter
under consideration. Malaise trap replicates should be
considered to avoid problems associated with trap damage or
loss and to demonstrate that existing richness has been
adequately sampled. Three replicates are suggested as the
minimum in richness studies; depending on the statistical
design additional replicates may be required in quantitative
studies.
References
Townes, H. 1972. A light-weight Malaise trap.
Entomological News 83:239-247.
