The Glasgow Naturalist (online 2016) Volume 26, part 3. Xx-xx

material ( varying in size between 0.9 and A prodigious collembolan 1.6 mm and blue/black in colour) as Hypogastrura ?litoralis based on Hopkin's key (2007), although I 'swarming' event on Kames Bay, did not have the best clearing chemicals available Millport (necessary for detailed appreciation of species- specific limb setation patterns). Their true identity P.G. Moore was subsequently confirmed authoritatively as the commoner H. viatica by Dr Peter Shaw, who informs 32 Marine Parade, Millport, Isle of Cumbrae KA28 me that many ' maritima' records are likely 0EF to be that species.

E–mail: [email protected] Davenport (1995) described zooplankton strandlines on the sub-Antarctic island of South Georgia that constituted a predictable food supply Alerted by a friend to the presence of “patches for shore-foraging sea birds. The unpredictability of looking like black oil but seething with minute the littoral collembolan bonanza herein described creatures” on the high- mark at Kames Bay, leaves open to question whether any shoreline Millport, Isle of Cumbrae (OS Grid REF: NS550173) predators might have benefited; birds would be the on 5 August 2016, I set out to examine the cause of most likely opportunists. Hopkin (1997) listed a his concern. Several reports exist concerning mass host of species recorded as preying on : strandings of insect swarms (Coleoptera, sawflies juvenile toads, lizards, birds and a number of and Tipulidae) dying at sea and being cast-up on the groups (harvestmen, pseudoscorpions, high-tide line of beaches in Britain (Scott, 1926a,b). beetles, mites, wasps), but these examples related to Anticipating, however, that the cause of this sighting fully terrestrial environments. might be stranded rafts of collembolans, my suspicion was soon confirmed. But I have never ACKNOWLEDGEMENTS seen patches of such size locally. The biggest patch, I am grateful to Mr Ian Frame for drawing my several animals deep and more-or-less rectangular attention to this phenomenon and to Dr Peter Shaw in shape, measured some 110×22 cm. It alone must, (Roehampton University) for definitive conservatively, have contained tens of millions of identification of my material. animals. Some dozen-or-so smaller patches were scattered about: in depressions in the sand, among REFERENCES the rocks and stranded seaweed, all within a few Barrett, J.H. & Yonge, C.M. (1958). Collins Pocket metres of one another. Guide to the Seashore. Collins, London. Davenport, J. (1995). Upwelling-generated plankton The common scavenging collembolan Anurida strandlines: important predictable food sources maritima () is often reported high on for seabirds at Husvik, South Georgia. Marine marine shores (Dexter, 1943; Barrett and Yonge, Biology 123, 207–217. 1953; Morton, 1954). Due to its hydrophobic cuticle, Dexter, R. W. (1943). Anurida maritima: an it is frequently observed being blown in rafts across important sea-shore scavenger. Journal of the surface of rock pools. I have certainly witnessed Economic Entomology 36, 797. such rafts locally, perhaps containing hundreds of Hopkin, S.P. (1997). Biology of Springtails (Insecta: individuals, many times in the past but I have never Collembola). Oxford University Press, Oxford. seen writhing masses of collembolans on this scale Hopkin, S. P. (2007). A key to Collembola on a sandy beach before. The propensity to 'swarm' (Springtails) of Britain and Ireland. FSC among collembolans, especially Hypogastruridae, Publications, Telford. has been widely reported (Turk, 1932; Hopkin, Morton, J. E. (1954). The crevice fauna of the upper 1997). Hopkin (2007:4) noted: “swarms occur at Wembury. Journal of the following synchronised reproduction in conditions Marine Biological Association of the U.K. 33, 187– of ideal humidity and temperature and abundant 224. food supply.” Swarming seems likely to be a Sankey, J.H.P. (1952). Swarming of Achorutes dispersal strategy. Sankey (1952) reported a swarm longispinus Tullb. Entomologist’s Monthly of the species Ceratophysella longispina Magazine 88, 92. (Hypogastruridae) on a vertical chalk surface Scott, H. (1926a). Coleoptera in the sea. adjacent to a road in Surrey that was estimated to Entomologist’s Monthly Magazine 62, 15. contain 100 million individuals. Morton (1954: 199) Scott, H. (1926b). Coleoptera, sawflies and Tipulidae stated “Anurida maritima often swarms” without drowned in the sea. Entomologist’s Monthly giving details. However, I was unconvinced that the Magazine 62, 165–169. Kames Bay swarm was of that species. After Turk, F. A. (1932). Swarming in Collembola. Nature microscopic examination, I tentatively identified my 129, 830–831.