62 OTHER 'MYRIAPODS' 



adjoining tergites to represent a single somite; but differ from 

 them in the structure of the two pairs of jaws, in having the end of 

 the antennae branched and in the possession of only twelve somites 

 and ten pairs of limbs of which nine have a locomotory function, 

 the first pair being reduced to mere buds. In addition the legs are 

 very widely spaced, tracheae are absent and five pairs of long tactile 

 bristles are attached to the sides of the body. 



Pauropods are minute Arthropoda measuring only about one- 

 twentieth of an inch in length. The first was discovered by Lub- 

 bock in 1886. They have since been found in Europe, Asia and 

 America where they inhabit damp situations beneath decaying 

 leaves, logs and so on. In some (Pauroptis spp.) which are more 

 active in their movements, the body is narrow, compared with its 

 length; but in the more sluggish forms (Eurypauropus spp.) it is 

 very wide, its sides and front being produced so as to conceal the 

 legs and head. At the present time six families are known to science, 

 but little information is available about their ecology and distribu- 

 tion other than that they are believed to be generally distributed 

 except in the arctic, antarctic and desert regions of the world. 

 Indeed, owing to their concealed habits they are sometimes be- 

 lieved to be rare, but Starling (1944) estimated an annual average 

 of 1,672,704 per acre (to a depth of 5 inches) in oak stands on clay 

 soil and 2,178,000 in pine stands on sandy loam in the Duke 

 Forest, North Carolina. Five times as many Pauropods were found 

 in oak humus on clay soil as in the same level under pine stands 

 on sandy soil, and his observations suggested that moisture and 

 temperature are the two main factors that affect the distribution of 

 these animals. The greatest number was collected from sandy soil 

 when the moisture percentage of the oven-dry weight was 11-20%. 

 In clay soil Pauropods appeared to prefer 21-30% of moisture. 

 The optimum range of temperature based on activity and mortality 

 rate when Pauropoda were placed in constant temperature cabinets 

 was found to be 16-20° C: the optimum, based on field observa- 

 tions, 17-23° C. Summer appears to be the most favourable season 

 for development and activity, and eggs were obtained in June and 

 July. A correlation appears to exist between optimum temperature 

 for fungal growth and a high incidence in Pauropod distribution 

 which may be related to their feeding habits. 



