Dear Readers, this week I have decided to have a little break from the quiz: it may be that once a week was too much for people to fit into their increasingly busy lives. Tell me if I’m wrong, though! I do hate to disappoint.
Instead, I wanted to tell you about an insect that I had never knowingly met in my entire life. As I arrived home from the Post Office (always something of a palaver) I noticed something running down my neck. I gingerly reached behind me and pick it off and there, just about the size of a lentil, was a very shiny black beetle.
I lifted my hand to get a better look, and the creature launched itself into the air, with the kind of distinct ‘ping’ that I associate with fleas. I was so surprised that, there and then, I googled flea and beetle, and here we are.
Now, you allotment holders have probably made the acquaintance of flea beetles in your battles to preserve your brassicas, because the RHS website describes how some species of flea beetle munch on everything from turnips to cauliflowers. These are largely members of the Phyllotreta or Psylliodes genuses (genii??). Have a look at the splendid back legs on the beetle below.
And here is a lesser striped flea beetle (Phyllotreta undulata).
But how good are they at jumping? My new favourite beetle book, ‘Beetles’ by Richard Jones in the New Naturalist series, has this to say about flea beetles and their jumping prowess:
‘...a flea beetle achieves a take-off velocity of 2 m/s (10 kilometres per hour), accelerating at more than 270g, and can easily jump 100 times its own body length (Brackenbury and Wang 1995).
I looked to see if there were any videos of the little darlings performing their acrobatics, but sadly all there are are various films to ways to exterminate them. According to Jones, the beetle’s jumping ability used to be a way of controlling them:
‘A traditional method of controlling Phyllotreta nemorum flea beetles on turnips, cabbages and kale was to push a light wheeled framework of heavily tarred boards along the edge of the crop; the startled beetles jump and are caught on the sticky tarred surfaces (Anon 1895)‘.
But all is not lost, because Jones is sure that the beetles don’t just randomly ping into the air, but may have a targeted landing spot – as we saw a couple of weeks ago, beetles are among the many insects that have hidden wings and can fly.
Some flea beetles can be very pretty, too. Have a look at the Willow flea beetle (Crepidodera aurata) with its golden carapace.
And not all flea beetles are pests – the beetle below feeds on mallows and is Nationally Scarce. How smart it is, with its orange head and teal-green wingcases!
These days, many gardeners look for kinder methods to deter flea beetles. One is to grow radishes as a kind of ‘bait’ for the insects, because larval flea beetles don’t feed on roots, and so they will be unharmed. Companion planting of mint, thyme and catnip is supposed to disguise the smell of the brassicas (though with catnip you might not have any cabbages left anyway once the local cats have had a good role). Tachinid fly larvae also eat the beetles, and the adults are useful pollinators. In other words, put that tar-covered board down, people! There are better ways of resisting the excesses of these extraordinary invertebrates.
And finally, here’s a thing. On the island of Lundy in the Bristol Channel, there is a species of cabbage which only grows on this tiny scrap of land. The Lundy cabbage (Coincya wrightii) is not a particularly attractive plant (it looks rather like oil-seed rape) and, fortunately for it, it is not particularly toothsome – it has been said to taste of ‘triple-distilled essence of brussels sprout’ and we can all imagine what I think about that.
Now, living on the Lundy cabbage are several insects that are completely dependent on the plant and who live nowhere else. And one of them is the Lundy Flea Beetle (Psylliodes luridipennis), a tiny metallic beetle that has been isolated from all those other West Country flea beetles for long enough to become its own separate species.
I love the way that island plants and animals often go their own way and, over time, become separate species, but there is a high level of risk involved: if the Lundy Cabbage becomes extinct, so will the Lundy flea beetle (and several other insect species as well). The whole island is managed by the National Trust and the Landmark Trust, and they are well aware of the risks of alien species such as rhododendron, which at one point threatened to overwhelm the whole island (as it does). Fortunately, there has been much uprooting, and some burning, and it looks as if the Lundy Cabbage and its dependents are safe for the time being. It all goes to show how tightly linked natural communities are, and how removing one pillar, even in the form of a particularly noisome cabbage, can bring the whole lot tumbling down.
Photo One by gailhampshire from Cradley, Malvern, U.K / CC BY (https://creativecommons.org/licenses/by/2.0)
Photo Two By Udo Schmidt – Flickr: Psylliodes chrysocephalus (Linné, 1758) converted to .jpg, CC BY-SA 2.0, https://commons.wikimedia.org/w/index.php?curid=20047623
Photo Three byAfroBrazilian / CC BY-SA (https://creativecommons.org/licenses/by-sa/4.0)
Photo Four by gailhampshire from Cradley, Malvern, U.K / CC BY (https://creativecommons.org/licenses/by/2.0)
Photo Five By TristramBrelstaff – Own work, CC BY-SA 3.0, https://commons.wikimedia.org/w/index.php?curid=18917102
Photo Six by James Lindsey at Ecology of Commanster / CC BY-SA (https://creativecommons.org/licenses/by-sa/2.5)
Photo Seven By Rodw – Own work, Public Domain, https://commons.wikimedia.org/w/index.php?curid=4535009
Photo Eight by Roger Key from https://www.flickr.com/photos/roger_key/2677474521