Friday, 6 June 2014

The Hogweed Restaurant

Hogweed, Heracleum sphondylium, is a very important plant for insects,and therefore entomologists, and it is now coming into flower. This member of the Carrot family, Apiaceae. is now to be found in abundance on roadside verges, field margins and woodland edges.

Many members of the Carrot family only secrete small amounts of nectar and therefore only attract "small fry". Hogweed produces it in such quantities that even honey bees find it worth their while to work it. And of course, pollen is also available.

I visited the Wildlife Trust reserve of Boddington Meadow earlier today and decided it would be interesting to record a few of Hogweed's visitors. The umbels of white flowers were a feature of the meadow's edge and some were gaining a foothold (sorry, roothold) in the meadow itself.

Hogweed mined by the larvae of Phytomyza spondylii.
Boddington Meadow L.N.R.  5 June, 2012

Almost immediately I noticed that it wasn't just the flowers providing sustenance for insects; the leaves were being utilised too. These mines are the work of an agromyzid fly, Phytomyza spondylium. Like many two-winged flies, this species has no common name.

A male Volucella pellucens on hogweed.
Boddington Meadow L.N.R. 5 June, 2014

The handsome hoverfly, Volucella pellucens, was present. With the clear white patches at the front of the abdomen and the dark areas on the wings it is easily recognised. Being a common species an entomologist will soon become familiar with it, not least because it frequently visits gardens. The large compound eyes are almost touching, showing that it is a male.

Epistrophe diaphana on hogweed at Boddington
Meadow.  5 June, 2014

Another hoverfly - also a male - was present but little more care is needed to identify this species. It is Epistrophe diaphana, again a fairly common species, and seems to have become more widespread in recent years. I think we can all agree that it is a rather good wasp mimic.

Merodon equestris

Many hoverflies mimic bees too. This is Merodon equestris, a very variable insect which, in all forms, is a bumblebee mimic. Although a very handsome creature it can be a pest, and its common name of Large Narcissus Fly hints at the problem. Its larvae will burrow into the bulbs of daffodils but, in the wild, the bulbs of bluebells are more likely to be the target. There is a gap between the eyes, indicating that it is a female.

The next insect to present itself was a bee. Although not immediately obvious, it has four wings, whereas hoverflies and their relatives make do with two. I am not a hymenopterist and generally don't record bees, wasps and their kin, but I'm pretty confident that this is Andrena cineraria, one of the so-called mining bees. It is not infrequent in gardens.

A calliphorid fly, Lucilia richardsi, on hogweed at
Boddington Meadow.  5 June, 2014
Dozens of other fly species were present but not all could be called photogenic, so I will include just one more. This smart "greenbottle" is in fact a blowfly, i.e. a member of the family Calliphoridae. The females are very tricky to identify but fortunately the specimen I photographed was a male. It turned out to be the relatively uncommon Lucilia richardsi; in truth it is probably quite common but entomologists often seem to overlook bluebottles and greenbottles, so they get under-recorded.

So on to beetles.

Anyone studying beetles. i.e. coleopterists, soon becomes familiar with this distinctive species. It is Malachius bipustulatus and, with its green elytra (wing cases) tipped with red it is unlikely to be confused with any other beetle. It's common name is, unsurprisingly, The Red-tipped Flower Beetle.

But it is the Cantharidae which are most associated with hogweed. Indeed, one cantharid beetle, Rhagonycha fulva, is often referred to as The Bonking Hogweed Beetle because males and females meet on the flower umbels to mate. I was a little early in the year for the B.H.B. but several of its relatives were present. The one shown is Cantharis rustica, a fairly large cantharid common everywhere.

So, as can be seen, hogweed is a wonderful lure for insects of many kinds. This species will flower, albeit, more spasmodically, through to early December, but is at its best over the next few weeks. It hardly needs to be said that I will be keeping a close eye on the flowers from now on. 

Of course, insects were abundant elsewhere at Boddington Meadow. More about that later...

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