SPIDERS 159 



water-skater and can remain submerged for long periods if 

 necessary. 



To summarise, aquatic spiders are known from several families 

 including the Agelenidae, Lycosidae, Pisauridae, Argiopidae, 

 Clubionidae, Linyphiidae, Salticidae and Thomisidae. The ex- 

 tent to which they live beneath the surface varies and some can 

 walk about comfortably with a bubble of air surrounding their 

 bodies whilst others rely on finding some cranny containing air or 

 enclose themselves and a supply of air in a silken cell. The subject 

 has been reviewed by Bristowe (1930b). 



The majority of spiders live on the surface of the soil, some in 

 burrows, others sheltering under stones, logs or beneath the debris 

 of fallen leaves in forests. Most of the Theraphosidae choose any 

 kind of retreat, living under stones or rubbish on the ground and 

 in cracks in trees. Some dig a simple cell which they line with a 

 slight web of silk. For the most part they are active forms and 

 wander about at night in search of prey. The most perfectly con- 

 structed burrows are those of the Ctenizidae, which dig with the 

 aid of a comb -like rake of large spines on the margins of their 

 chelicerae. The walls of the tube in which the spider lives are lined 

 with a waterproof coating of earth and saliva to which a layer of 

 silk is applied: as the spider grows, it enlarges its burrow, the 

 entrance to which is closed with a trap-door. The first description 

 of this interesting device was given by Patrick Brown in his Civil 

 and Natural History of Jamaica, London (1756). Seven years later 

 the careful observations of the Abbe Sauvages on the nests of 

 Nemesia caementaria, which he discovered near Montpellier, were 

 published. Although trap-door spider nests attracted popular 

 attention thereafter, it was not until Moggridge (1873) published 

 his studies on the habits of these animals that any comprehensive 

 treatment was accorded them. 



Moggridge was able to distinguish four types of nest among the 

 species he studied. The first was a simple cylindrical tube with a 

 thick 'cork door', the second had a thin 'wafer door', the third a 

 thin outer door with a second door part of the way down, while the 

 fourth was the most complicated: a tube capped on the outside by 

 a thin door and having an oblique side tunnel at the entrance to 

 which was another trap-door. Since then several other types of 



