36 Routes from the Sea 



Some larvae are associated with particular species of plants. Some 

 are strictly vegetarian, but nine species are listed that are predators 

 on other mosquito larvae. 



When marshes, swamps, and pools periodically dry up, many of 

 the animals which live in such situations are able to survive. Palu- 

 dine types are commonly able to burrow, encyst, or go into some 

 other type of dormancy. The ability of the lung-fishes to live in a 

 cocoon of mud for months is well known (Smith, 1931). Hall 

 (1901) describes the habits of two eel-like galaxid fishes from 

 Tasmania and New Zealand. These burrow in mud or soil. One 

 swims freely in water, but the other is accustomed to live in mud, 

 swims with difficulty, and dies quickly when submerged in clear 

 water. In Siam aestivating fishes burrow as much as two feet in 

 soil and remain without water for three or four months. When the 

 rainy season comes, serpent heads and climbing perch commonly 

 migrate over the land (Smith, 1927) . In Australia there are dragon- 

 fly nymphs which can live in sand without water. Their bodies be- 

 come so dry that they crackle when handled, but when such animals 

 are put in water they become active in a few minutes (Tillyard, 

 1917) . In Hawaii some dragon-fly nymphs have left the water al- 

 together. They lurk at the bases of leaves and watch for prey 

 (Perkins, 1897) . The phyllopods and certain other small animals 

 that live in temporary pools on prairies and steppes are able to 

 stand great variations in environmental conditions. The eggs of 

 some pool crustaceans will not hatch until they have been dried and 

 subjected to extreme temperatures (Davenport, 1908) . 



The peculiar combination of variable environmental factors which 

 obtains in marshes, swamps, and pools is conducive to the produc- 

 tion of hardy animals and modifications toward land types. Variable 

 temperatures and salinities permit only animals to survive which are 

 able to stand such changes. Lack of oxygen and water makes air 

 breathing and coverings which resist desiccation essential. With. 



