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➤ Where do the bugs go in winter?

Published on May 3, 2015, by in All, News and musings.

As winter progresses and vegetation in the meadow plots dies back, some people will like the look of them more than others. Similarly, the appeal of the different plots will vary for different small creatures, looking for shelter and food. One of the aims of the experimental plots is to work out what insects need in a meadow to survive, and which of the treatments provides this for the greatest range of insects. We will then have a better understanding of how to support diverse and important invertebrate communities in our urban green spaces.

In summer, it is easy to see how bright flowers can attract important pollinating insects, or how lots of healthy green leaves can feed more caterpillars, which in turn attract more birds. But once attracted, how do the meadows retain these valuable species from one year to the next? To sustain a population of insects they have to be present throughout the year, to allow all the different life-stages to be completed. Adult and immature insects vary in their habitat needs. At each stage the animal can look quite different, eat different food and live in a different part of the meadow environment. For example, a butterfly may need flowers in June for it to feed, reproduce and colonise the area. It will lay eggs on leaves and produce a larval stage – a caterpillar in this case. They might need a specific food plant on which the caterpillar can feed. Once full grown an insect larva may need a curled leaf, a plant stem, a layer of leaf litter or an undisturbed patch of soil in which to ‘pupate’ or turn into a dormant chrysalis. When spring arrives, the adult will tentatively emerge and sit on a twig or stem to dry its wings before flying off in search of another suitable plant to start the cycle all over again.

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Collecting invertebrates using a pooter in the winter winds

One of the key elements of the meadow design is to have varying height and structure, in which different insect life-stages can survive. To see whether the structurally diverse plots are helping invertebrates survive over winter more effectively than traditional mown grass, the team from the University of Sheffield needed to take samples from within the meadow plots during February. This is not an obvious (or attractive) time of year to be out looking for insects. But, despite the cold, foggy and wet conditions, our team managed to record a great many species. You would be surprised how many spiders, beetles, caterpillars and flies are active down at the base of what seems to be just dead weeds. There is a thriving community of overwintering animals that call the meadows home all year round, whether as adults or a more dormant stage such as pupae or larvae. Without this continuous habitat throughout the year, many species would have to attempt to re-colonise as adults every year instead of establishing a home population.

To find these creatures during the winter required a more direct method of searching than during the summer. Nets, which work well in the warm sunshine, soon get wet-through in the winter. So, our team were down on the ground searching by hand and sucking out anything that moved with ‘pooters’ and tweezers. We also looked into the top layer of soil and broke open tall plant stems and seed heads to see what might be hiding in these warmer shelters.

When the data is analysed, their efforts in the freezing temperatures should reveal whether the brown and flattened vegetation – Teasel stems, seed heads, fallen grass, undisturbed soil and layers of dead leaves – is supporting more creatures than mown grass or other vegetation mixes during the cold winter months. We will then have a better understanding of whether the meadow plots help support healthy populations of the bees, butterflies and other insects we appreciate so much in summer.

Briony Norton

 
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