194 APTERA 



1 



the reverse is the case. They are excessively numerous in 

 individuals ; they are found nearly everywhere on the surface of 

 the ground in climatic conditions like those of our country, 

 while no less than sixteen species have been found in Nova 

 Zembla and one each in Kerguelen and South Georgia. One 

 species, if not more, of Poclura, lives on the surface of stagnant 

 waters, on which the minute creatures may frequently be seen 

 leaping about in great numbers after being disturbed. 



In 1874 the plain of Gennevilliers in France was copiously 

 irrigated ; in the following year the soil was still very damp, and 

 there existed numerous pools of stagnant water, on the surface 

 of which Podura aquatica was developed in such prodigious 

 quantity as to excite the astonishment of the inhabitants of the 

 region. 



Accounts have been frequently given of the occurrence on 

 snow and glaciers of Insects spoken of as snow -fleas, or snow- 

 worms. These mostly relate to Poduridae, which are sometimes 

 found in countless number in such situations. The reason for 

 this is not well understood. According to F. Low,^ on the iTtli 

 of March at St. Jacob in Carinthia, Parson Kaiser observed, on 

 the occurrence of the first thaw-weather, enormous numbers of a 

 Podura (? Achorutes murorum) on the surface of the snow for an 

 extent of about half a mile, the snow being rendered black in 

 appearance by them ; eleven days afterwards they were found in 

 diminished numbers on the snow, but in large quantity on the 

 water left by its melting. This account suggests that the 

 occurrence of the Insects on the snow was merely an incident 

 during their passage from the land, where they had been 

 hibernating, to the surface of the water. 



One little member of the Lipuridae, Anurida maritima 

 {Li'pura maritima of Lubbock), has the habit, very unusual for an 

 Insect, of frequenting salt water. It lives amongst the rocks on 

 the shores of the English Channel, between high and low tide- 

 marks. Its habits have been to some extent observed by 

 Laboulb^ne ^ and Moniez ^ ; it appears to be gregarious, and when 

 the tide is high, to shelter itself against the commotions of the 

 water in chinks of the rocks and other positions of advan- 

 tage. When the tide is out the Insects apparently delight to 



^ Verh. zool.-hot. Ges. Wicn, viii. 1858, p. 564. 

 2 Ann. Soc. ent. France, 4th ser. iv. 18G4, p. 705. 

 ^ Rev. Mol. Norcl France, ii. 1890, p. 347. 



