Saturday, 7 February 2009

Challenging times for the entomologist

The winter months can be difficult for those of us with an interest in invertebrates. The short days, low temperatures and relative lack of activity on the part of the objects of our chosen study, make a trip out seem hardly worth the effort. Roll on the warm days of summer, the air filled with the soft drone of a myriad of insects and the grass alive with chirping grasshoppers and bush crickets! Of course, the insects that we seek have not necessarily vanished with the arrival of winter; many are holed up, hidden within the stems of plants, under bark or in subterranean chambers awaiting the arrival of the warming days of spring. It is just a case of getting out there and finding them. In fact, winter can be a particularly rewarding time for finding certain creatures.

Finding invertebrates is very much about knowing where and when to look. This means that there are some habitats and microhabitats that are not worth examining during the winter because they will yield very little of interest. Others, however, are very much worth a look. One of these is flood debris, the vegetation and detritus that has been deposited by rivers that have topped their banks. The best of this debris is the finer material, formed from small pieces of grass and other vegetation. Within such material it is possible to find many hundreds of small beetles, from various families. The material needs to be examined carefully and, ideally, sieved so as to remove the larger debris. A hand lens can be particularly useful, especially as some of the beetles will remain motionless for some time after first being disturbed.

Another worthwhile microhabitat exists behind pieces of loose bark. In addition to finding some of our larger beetles, you may also find woodlice and other invertebrates protected, behind the bark, from the worst of the winter weather. Make sure that you do not remove too much bark and remember to replace what you can to ensure some shelter remains.

Other methods can also deliver some interesting species. Many entomologists give a piece of summer vegetation a good hard tap over a white tray to dislodge whatever happens to be feeding upon it. The same approach can work in the winter, revealing the smaller number of species still active on the tree, for example some of the weevils that feed on fungi. The first of the season’s catkins are also worth investigation, also producing a number of beetles of interest. You can even use pitfall traps (a small plastic tub sunk into the ground), baited with fish and placed in a Rabbit burrow. This should draw out some of the more interesting subterranean beetles!

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