IlAi.UKiri' — The Acarina of Ihc Seanliore. 109 



fissures, where there was suflicient air to support tlicni during the time their 

 haunts are covereil witli water. I'ut a little observation of the creatures soon 

 proves that this is an erroneous idea. It is quite true that the inoru active 

 mites (Rhyncholophus, Bdella, &c.,) may often be seen moving about freely on 

 the shore at low tides, more especially during bright weather, and tiiey must 

 necessarily seek retreats to protect themselves from the tides. Yet their 

 habitual dwelling-places are in the sheltered spots, such as crevices, rock- 

 fissures, and under embedded stones, as anyone who has collected these 

 animals can easily observe. These habitats are always such as have been for 

 long undisturbed, and where air is imprisoned during high tides, and there 

 the mites and their associates are found even in places that have not been 

 covered by water for several days, as in the Pelvetia and Orange Lichen 

 zones. Indeed, a boulder for long embedded in sandy mud, or a flaking rock, 

 often presents an interesting sight on being disturbed. It will be noticed 

 that, although covered twice a day by the tides, the freshly exposed surfaces 

 are not saturated with water, but are just moist, or in the higher zones fairly 

 dry, and iu the favoured places are peopled by a variety of insects, mites, 

 and other animals. There may be found large colonies of the common shore 

 spring-tail Anurida marUima, with myriads of their cast skins in a dry 

 condition, and attendant predaceous mites, beetles (Aepus, Diglotta, 

 Micralymma), and false scorpions [Ohisiicm maritimum). 



Higher up on the shore in the gravel, sand, and shell association, at about 

 high-water mark, Acarina are often found in places wliere there are no such 

 retreats, but in this case the mites are only occasionally wet or sprayed, 

 by the spring tides, and are evidently quite at home in their habitat. 

 Comparatively few species have succeeded in establishing themselves here, 

 though they may be numerous enough in individuals. 



A glance at the table (p, 111) giving the zonal distribution of the intertidal 

 Acarina makes it clear that the number of species becomes suddenly much less 

 below the Orange Lichen zone, and in order to understand this it must be 

 remembered that this zone is normally not covered by water for a large 

 proportion of the tide-cycles. Apparently a majority of the species have not 

 succeeded in penetrating lower than this zone, and, as might be expected, they 

 are lai-gely such as are not confined to an intertidal habitat; this applies in 

 particular to the family Oribatidac. This is also a less nuvrkcd falling-oil' 

 below the Pelvetia zone, and here again there is less flooding ihan in the case 

 of the lower zones, which are uoriually covered by the two daily tides. Tlie 

 list contains sevcnty-seveu species, and of these (e.xcliuling the Halacaridae) 

 we find that about twelve species range from the Orange Lichen down to tlie 

 Serratus, and in a few cases even to the Lauiinaria zones. In the localities 



