Classy jumper

The recent improvement in the weather has triggered a burst of insect life as they respond to the early summer heat. This has shifted the hazards as I run the local lanes, from leaping giant puddles to avoiding swallowing the local insect fauna. Whilst on a slower ecological circuit, I was drawn to the numbers of flies, beetles and bees feasting on the abundant Alexanders flowers and other plants. It was however a red and black ladybird-coloured insect that particularly caught my eye, poised on a nettle. I took a couple of images before my macro lens became too intimate with the beast and in a flash it was gone. Back at home I was quickly able to identify it as one of our most visual frog hopper species, the Red-and-black Froghopper (Cercopis vulnerata). These bugs are also known as ‘spittle bugs’ and cuckoo-spit insects’, due to their nymphal stage habit of living in a protective mass of froth or spittle (Chinery, 1977).

When it comes to jumping stakes, few would bet against the flea when taking account of relative body weight. It turns out that froghoppers, such as C. vulnerata, produce a substantially better jumping performance. Starting with my puddle leaping efforts with a take-off force of about 2-3 times my body weight, the flea manages about 135 times, and froghoppers more than 400 times (Burrows, 2006). This is a very useful if you want to avoid predation or being eaten by a grazing cow. Researchers have shown that the key to this jumping performance is a spring-loading mechanism called the ‘pleural arch’, which the insect compresses like an archer’s bow in readiness for leaping to safety (Patek, et al., 2011). It is even cleverer than this when you consider the materials used to form the pleural arch; a sophisticated combination of chitinous material to store energy and ‘resilin’ to provide flexibility and shape restoration, has drawn comparisons with high performance composite bows (Patek, et al., 2011).

Such innovative mechanisms adopted by insects has inspired engineers and biologists to consider applications for human inspired devices. If we get another wet spell as bad as this April, I would be interested in a ‘human friendly pleural arch’ device to better avoid the puddles.

Burrows, M. (2006) Jumping performance of froghopper insects. Journal of Experimental Biology, 209: 4607-4621.

Chinery, M (1977) A Field Guide to the Insects of Britain and Northern Europe. London: Collins.

Patek, S.N., Dudek, D.M. and Rosario, M.V. (2011) From bouncy legs to poisoned arrows: elastic movements in invertebrates. Journal of Experimental Biology, 214:1973-1980.

Limestone lovers

Berry Head in South Devon is quickly becoming one of my favourite haunts with its rich botanical landscape and marine wildlife. Last September I blogged about one of its specialities, the White Rock-rose (Helianthemum apenninum), a nationally rare species (see http://nicksnaturenotes.blogspot.co.uk/2011/09/last-white-rock-rose.html). The unusual mix of physical geography and chemistry provided by the Devonian limestone sea cliffs of Berry Head provide conditions for the White Rock-rose shared only by a handful of other sites in the South West. I was visiting it again this weekend with friends and showed off the White Rock-rose amongst other more common plants. Towards the end of the afternoon we wandered up to the remains of the fort in search of summer migrant birds amongst the scrub. Resting my arms on the battlements and enjoying a Whitethroat and possibility of Cirl Buntings, I became curious about a stunted-looking plant which I had almost leant on. Closer inspection revealed what looked like a bonsai version of an umbellifer, a dwarf parsley or carrot plant. My companion with much pleasure eventually identified it as Honewort (Trinia glauca), which is indeed a member of the carrot family and another local limestone specialist. Apparently, in turf closely grazed by rabbits, plants of Honewort grow to no more than a few centimetres tall (BRC, 2012), as was the case with many of the Berry Head plants that we observed.

When I got home I looked at the distribution map on the National Biodiversity Network's Gateway (see http://data.nbn.org.uk/gridMap/gridMap.jsp?allDs=1&srchSpKey=NBNSYS0000003662) and fascinatingly it is found in almost the same isolated areas as the White Rock-rose. These rare fragmented habitats of dry limestone, with short-grazed south facing aspects have created almost identical conditions for such specialists to cling on to their slopes. However their hold is truly precarious, the species being listed as ‘Near Threatened’ (BRC, 2012). The challenge for the Honewort is made more challenging as it is dioecious (having separate male & female plants, requiring cross-pollination) and has poor seed dispersal, most likely reliant on ants (Carvalheiro, et al., 2008).

These two limestone loving species are literally hanging on in Britain, exposed to human disturbance.  This makes it all the more important to value these wonderful wildlife hotspots and for me to take more care where I lean my tired ‘binocular-ed’ arms.

BRC (2012) Online Atlas of the British and Irish flora [online] http://www.brc.ac.uk/plantatlas/index.php?q=plant/trinia-glauca [Accessed 7/5/12]

Carvalheiro, L.G., Barbosa, E.R.M. and Memmott, J.(2008) Pollinator networks, alien species and the conservation of rare plants: Trinia glauca as a case study. Journal of Applied Ecology, 45: 1419–1427

National Biodiversity Network's Gateway  (NBN) (2012) Grid map of records on the Gateway for Honewort (Trinia glauca) [online] http://www.brc.ac.uk/plantatlas/index.php?q=plant/trinia-glauca [Accessed 7/5/12]