In praise of rat tails

The other week, a fellow wildlife gardener tweeted her delight at attracting rat-tailed maggots to her nettle feed. It might seem an odd thing to be delighted about but not if you are a gardener and happen to know what these unpleasant-sounding creatures turn into. Rat-tailed maggots are the larval stage of certain hoverflies and hoverflies, as any wildlife gardener will tell you, are considered to be great allies in the garden.

Looking rather, well, ‘maggot-like’ these larvae get their name from the long breathing tube at their rear. A number of different hoverfly species produce larvae of this form, including the familiar drone-fly Eristalis tenax, which (as an adult fly) mimics a bee. In some species the ‘tail’ can be several centimetres in length, allowing the larva to remain hidden in the detritus that gathers at the bottom of a pool while still enabling the larva to take air from the surface. rad-tailed maggots are typically found in stagnant water, such as that which forms in farmland ditches or garden water troughs. Others make use of slurry, rot holes in trees and sap runs; it is easy to see how nettle feed emulates some of these peculiar habitats.

Not all hoverfly larvae live such a damp existence though. Some live under bark or within dead wood, while others live on the surface of plants where they hunt aphids – something which may seem surprising for a maggot-like creature lacking legs. It is these aphid-eating larvae that are really the gardener’s friend, rather than the other species that have no impact on potential pest populations. There are even some species that, dare I say it, feed on plants! Each of these larvae tends to show adaptations to its particular way of life. Aquatic species, for example, may have modified mouthparts that enable them to filter feed and to take organic matter from the ‘soup’ in which they live.

Quite a few species have larvae that are similar in appearance so that, even with a guide (believe it or not there is a field guide to these creatures) you have to rear them through to adulthood in order to find out what you have been looking at. I am not quite sure that I am ready to have a go at those species that live in manure or slurry but I think I could manage some of the stagnant water or dead wood forms. It is amazing to discover this part of the hoverfly lifecycle and to find creatures making the most of the opportunities that these rather unusual microhabitats provide. It is also amazing to see the adult hoverfly and to know just how very different things were when it was a larva.

The lure of Fennel

The fennel that dominates the small bed outside of our kitchen window is alive with insect life. To be honest this is the main reason why I have not moved it elsewhere, tolerating its scruffy domineering form because of the fascination I derive from a few minutes stood watching the many and varied insects that arrive to feast on its juices. At the moment it is the small yellow and black forms of hoverflies that catch my eye, so great is their number. This sudden influx suggests that these are immigrants, newly arrived from continental Europe and part of a wave of immigration that has also delivered the Silver-Y moths that emerge as soon as darkness falls.

Hoverflies have always struck me as interesting insects and, importantly, a group which it is possible to tackle because of the relatively small number of British species (roughly 270) and the relative ease by which most can be identified. Just as there is diversity in their adult forms, with some excellent bee mimics and others strongly reminiscent of certain solitary wasps, so there is diversity in their pupal forms. Some spend their pupal stage in tree sap, some in decaying vegetation and others in water or even dung! I didn’t say they were pleasant, merely interesting.

Of course, it is not just hoverflies that are attracted to the fennel. There are many other small flies, most belonging to families of flies that I have never been brave enough to tackle, plus various beetles, including many familiar ladybirds and soldier beetles. A walk around the rest of the garden soon reveals that the fennel is the main draw at the moment, with the very dry conditions of earlier in the year having greatly reduced nectaring opportunities elsewhere. Fennel has a deep tap root, allowing it to survive well in such dry conditions and, incidentally, making it rather persistent once established.

The attractiveness of the fennel has an obvious parallel away from the garden. Walk along a quiet Norfolk lane or explore a bit of waste ground and you will encounter other plants from the same family as fennel. These other umbellifers also do well for insects, with soldier beetles in particular a common sight feeding on the tiny flower heads. I would imagine that many of these visiting insects are rather short-tongued and that this is why they visit these smaller flowers.

Although fennel is a familiar culinary herb, sometimes used as an ornamental in borders, it has also become established beyond the garden gate. Its Mediterranean origins explain why the Romans brought it to Britain and also why, outside of gardens, it is largely restricted to southern parts of Britain.