There has been much going on so far this summer with our
Wheat Midge Natural Enemies Project. So
far, we have seeded our
plot
trial and have been collecting samples from the plots using a method
called pitfall trapping. This is similar
to what Hannah described
here
for the pea leaf weevil but these traps do not use a lure. The pitfall traps
used for this study are comprised of two containers and a funnel made out of
the top portion of a 2-Liter pop bottle.
As they are walking along the soil surface, arthropods fall into the funnel and
slide down into the trap, which contains a mixture of antifreeze and
water. This solution kills and preserves
them until we collect them each week.
Figure 1. (A) The
pitfall trap sits flush with soil in the middle a row in each plot. (B) The
pitfall sample after the inner container has been removed. Specimens are preserved in antifreeze
solution which is the pink liquid that can be seen in the photo.
The pitfall traps collect a variety of arthropods which includes a fascinating array of beetle species.
The beetles we collect come in all shapes and vary from 2 mm to 4 cm in
length. Some of the most exciting of
these are the beetle predators which are one of the main focuses of this study. The goal of this project is to provide a
unique comparison of beetle diversity and the rotation practices utilized by
growers in the Peace River region.
Figure 2. The biodiversity of beetles collected in wheat
can be seen in this sample from the 2015 pitfall trap collections.
Ground Beetles
Carabidae, commonly known as ground beetles, is the largest
family in the suborder, Adephaga, which comes from the Greek adephagos or ‘gluttonous.’ Gluttonous goes a long way in describing this
family, as ground beetles are voracious feeders and often are cited as important
predators. Ground beetles are known to
feed on aphids, cabbage root flies, Lepidopteran larvae, and many other pest
species. Carabid beetles make up the
vast majority of the beetles we pick up in our pitfall traps. Keep an eye out for them in the field; they
have long slender legs made for running and vary in color. Dark coloration generally denotes nocturnal
species and metallic coloration usually indicates species that are active
during the day.
Tiger Beetles
Though they may look quite different, tiger beetles are a
sub-order in the Carabidae family. Tiger
beetles have long, sickle shaped mandibles (mouthparts made for chewing) and
bulging eyes. The larval stage of these
beetles is known to create tunnels in the soil substrate. There, they lie in wait to ambush prey at the
opening of the tunnel. When their prey
walks by, the larva grabs it and drags it down to the bottom of the tunnel to
feed. The adults of these species are
rapid fliers and have distinctly long legs that allow them to run quickly over
the soil surface.
Rove Beetles
Staphylinidae, or rove beetles, are another important family
in terms of predation. Rove beetles
typically have shortened elytra that do not completely cover their abdomen. Elytra are the hardened forewings that characterize
all beetles. Having shortened elytra
allows rove beetles to maneuver more readily in the field. However, there is a trade off - shortened
elytra expose them to a greater risk of desiccation which makes them dependent
on humid habitats. Rove beetles are
great predators and can even be parasitic.
Check out this
link
to see one of the parasitic rove beetles (
Aleochara
spp.) that emerged from a cabbage root fly pupa that we collected in October
2015.
