HARVEST-SPIDERS 139 



pus morio, Oligolophus tridens, Lacinius ephippiatus, Platybunus 

 triangularis, Megabunus diadema and Phalangium opilio. Finally 

 certain species tend to live as adults above the field layer on bushes, 

 trees, walls and fences while their young stages are found nearer 

 the ground. These include Oligolophus agrestis O. hansenii, Odiellus 

 spinosus and Opilio parietinuSy but there is some overlap between all 

 three groups and most species migrate upwards as they mature. 

 This appears to be associated with the need for bigger prey, more 

 space to move in, mating and probably different temperature and 

 moisture requirements (Sankey, 1949b). In addition, Todd (1949) 

 has shown that many species of harvestmen are most active at 

 night when they show a tendency to migrate upwards on to trees 

 where the air is damper. This activity is correlated with the de- 

 crease in light intensity, increase in relative humidity and decrease 

 in temperature that occurs after dark. Thus in Wytham Woods, 

 some 4| miles north-west of Oxford, Leiobunum rotundum hunts 

 on the underside of Mercuralis perennis leaves during the day but 

 passes the night on the trunks of trees. 



A similar vertical migration was found to occur in Oligolophus 

 tridenSy and many other species show a vertical migration during 

 their life histories, as already mentioned. At the same time there is 

 usually a microhabitat separation in space and time, or both, be- 

 tween allied species of the same genus. L. rotundum and L. black- 

 walli resemble each other very closely but during their life histories 

 there is no habitat overlap in time until they both appear on tree 

 trunks at the age of six months, L. rotundum hatches about a 

 month in advance of L. blackwalli and retains this lead as it ascends 

 from one plant layer to the next. L. blackwalli is never abundant 

 and is found on the lower parts of the tree trunks while L. rotundum 

 is much more plentiful and is usually to be seen up to seven feet 

 above ground level. Similarly Oligolophus tridens is a dominant 

 field-layer form while the less abundant O. agrestis and O. hansenii 

 are found predominantly on tree trunks and amongst the branches. 



Food and feeding habits 



Harvest-spiders are primarily carnivorous and usually feed on 

 fresh or recently dead animal tissues, but they will also eat a varied 

 assortment of matter such as bread, fat, the gills of Chanterelle and 



