SOME INTER-TIDAL MITES FROM SOUTH-WEST ENGLAND By G. OWEN EVANS and E. BROWNING SYNOPSIS The distribution of ten species of inter-tidal Acari from south-west England is given, together with descriptions of Lasioseius fucicola Halbert (1920) and Chaussieria maritima sp. n. THE Acari of the inter-tidal zone comprise two main groups : those which are typically terrestrial and those which are restricted to the inter-tidal zone. The latter exhibit structural modifications associated with mites living under semi-aquatic conditions. The chief modification affects the ambulacra of legs II, III, and IV which become long, hair-like lobes a structure assisting the movement of the animal over a permanently moist substratum. Leg I, which is not usually used for locomotion, is normal. The inter-tidal Acari do not show any modification in the organs associated with respiration. This suggests, as Halbert (1920) has pointed out, that these animals are not enveloped by the sea water but inhabit crevices, &c., where air is imprisoned during high tide. Many species of mites are found under deeply embedded stones together with springtails, beetles, and pseudoscorpions. Others (Balaustium, Molgus) run freely on rocks at low tide, especially in sunny weather, but are forced to seek the shelter of rock fissures, &c., by the incoming tide. The major contribution to the study of sea-shore mites has been made by Halbert (1920). This investigator studied the distribution of Acari in relation to certain zones occupied by lichen and seaweeds. The richest population occurred in the zone lying between neap and high spring tide, a zone left dry for relatively long periods. There followed a marked decrease in the variety of forms towards low-tide marks. This was chiefly due to the absence of the terrestrial forms which formed the majority of the species around high-tide mark. Twelve species were recorded for the zones normally covered by the two daily tides. The Acari described in this paper were collected by one of us (E. B.) during mid-summer in 1947 and 1949. The collecting was by no means exhaustive and was restricted to the area between low-and high-water marks in the following localities : Devon 1. 'The Nest', Babbacombe, 11.7.1947, on rocks between tide marks. 2. Rock End, Torbay, 12.7.1947, on rocks between tide marks. 3. Carbons Head, Torbay, 13.7.1947, on rocks between tide marks. 4. Livermead, Torbay, 15.7.1947, on rocks between tide marks. 5. Oddicombe Beach, Babbacombe, 15.7.1947, on rocks between tide marks. 6. Carbons Head, Torbay, 17.7.1947, under stones below high-water marks. 7. Meadfoot Beach, Torbay, 18.7.1947, under stones below high-water marks. Dorset 8. Peveril Point, Swanage, 14.7.1949, under stones below high-water marks.
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