NOCTULE BATS ( N Y C T A L U S NOCTULA) SUMMER CHAFERS ( A M P H I M A L L U S D.
FEEDING ON SOLSTITIALIS)
THE relationship between Noctules and Summer Chafers has been described in the Transactions briefly by Ellis (1934) and Gilbert (1948) and in more detail by Barrett and Cranbrook (1964). From 27th June to 23rd July, 1964, I watched Noctules and Chafers at dusk in Westleton. Between the Dunwich and Blythburgh Roads was a barley field surrounded by sparse, ill-kept cherry hedges and a few roadside oaks. At 21.00 hours on 27th June, which was a fine, warm evening with a light north-west wind, I first saw large numbers of Chafers Coming up out of the barley, where eggs would have been laid in the soil two years previously. They flew or were blown towards the leeward edges of the field and formed noisily buzzing concentrations in the tree-tops and to a lesser extent in the hedges. I saw very few Chafers going further away from the field. Objects falling heavily from the trees on to the road proved to be copulating pairs, and sometimes groups of three insects clasped together. Noctules, their number probably far exceeding my highest count of eight, hunted the Chafers from 21.20 to 22.45 hours. They flew in wide circuits round the field just below the tree-top level, where they intercepted high-flying Chafers, occasionally in the open but more usually very close to the branches, and frequently dived to catch their prey low down over the barley. Bats from this group rarely appeared over the neighbouring barley fields or heathland. On 7th July I discovered an apparently distinct group of Noctules at a site over half a mile to the south along the Eastbridge Road. On four occasions I watched the groups in rapid alternation and could detect no interchange of individuals between them. At the second site Chafers came out of barley fields on either side of the road and congregated in a hundred yards length of the roadside hedges (composed of hawthorn and bramble) and more especially in the tops of two hedgerow oaks. The bats, at least fourteen but probably far more, behaved as described above but in addition frequently flew low across the road and very often hawked along the hedges as described by Barrett and Cranbrook. A nightjar hunted Chafers along the same Stretch of road on several occasions. My experiences with stones thrown as insect Substitutes amid the hunting bats differs from that described by Barrett and Cranbrook. A Noctule, eight times out of ten, could be induced to dive down to and frequently catch in its mouth an accurately thrown stone, only to release it immediately. When a bat ignored an accurately thrown stone the reason was generally obvious in
21 NOCTULE BATS that the bat was seen to catch and carry in its mouth a Chafer just before reaching the stone. After dark, when thrown stones became invisible to me, I repeatedly saw bats dive very low to spots, whence immediately came the sound of the falling stone. REFERENCES Ba et G and he E 1 f ra broo c
p l' We-rs. Trans. J c 5Suffolk ,? " ' Nat. - (]%4Soc. ) Noct1 u2le :Ba3ts47f.eeding on Cockchaf E11 S: 2 309 A' (1934) °bservations on Bats- Tram- Suffolk Nat. Soc. G be
° n BatS ^ WCSt Suff0lk'
Tmm Suffolk Nat Soc