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.

Soldiers and sailors line the lanes

Throughout the months of late spring and summer, the lanes of Norfolk are dressed with the soft white tones of umbellifers. These erect and architecturally interesting plants are members of the carrot family, with their narrow branching stems topped with groups of small white flowers. A succession of species flower as the months progress, starting with the cow parsley that is at its best during May. From late May through into July it is replaced by the somewhat less showy rough chervil, which in turn is replaced by upright hedge parsley come August. These are interesting and diverse plants, which occupy a range of habitats and include species that are edible (for example, alexanders), while others (such as hemlock) are deadly poisonous; hemlock is perhaps best known as the poison given to Socrates at his execution.

As a non-botanist, my interest in these plants is in the diversity of invertebrate life that they attract. Visit a patch of umbellifers on a fine day and you are almost certainly going to encounter some rather smart beetles, various small hoverflies and possibly even a scorpion fly or two. Some of the beetles most often encountered belong to a family called the Cantharidae, better known as soldier beetles. They are typically a couple of centimetres in length, with narrow parallel-sided bodies and brightly coloured wing cases (known as elytra), and they will be familiar to those who have spent anytime in the countryside during summer. There are 40 species of soldier beetle in Britain; many have red or yellow wing cases but others are dull blue or even black. Some authors refer to the dark coloured species as sailor beetles, reserving the name of soldier beetle for the red or yellow coloured species. While this may reflect an association with the traditional uniforms of the different branches of our armed forces, the distinction is pretty unhelpful in the field, especially when it comes to attempting an identification. This is because the colours shown by individual species of soldier or sailor beetle can be very variable; while one individual may be red, another of the same species may be a dirty brown or almost black.

The adult beetles and their larvae are fluid feeders and, while they may feed from plant material, they are typically carnivorous in their habitats, feeding on dead or injured insects. They will also tackle healthy live prey if it is small enough or slow enough to overcome without the risk of injury. These beetles, therefore, are not simply visiting the umbellifer flowers for nectar or pollen. Instead, they are here to find more substantial rewards, in the shape of other insects for food, or a mate to continue their lineage.