INSECTES AQUATIQUES D'UNE TOURBIÈRE 



533 



Drying up of the ponds favours prédation of aquatic species by those in- 

 habiting the surroundings. 



Variations of the water level may have catastrophic conséquences for the 

 eggs of aquatic insects. 



14. Prédation and cannibalism are regulative factors among the populations. 



— On the surface of the water, population régulation of Gerris results from 

 prédation of the young larvae by older larvae and by adults. 



— Dolomedes fimbriatus plays a décisive rôle in the disappearance of Lestes 

 sponsa. 



— Cannibalism is intense among dytiscid and hydrophilid larvae. 



— Where there is abundance of grass-frog tadpoles, the large species of 

 insect predators are attracted ( Dytiscus marginal is, Acilius sulcatus, 

 Notonecta glauca ) . 



— Formica rufa becomes a predator of aquatic species only when the ponds 

 dry up. The populations of this species are themselves regulated by the 

 green woodpecker (Picus viridis ) . 



15. The author has studied 43 ponds and 10 channels. In order to avoid taking 

 too many and too abundant individual samples, the fauna has been observed 

 in situ. 



Trapping and marking were also done as well as breeding in captivity in 

 order to complète the observations in the field. 



16. The author finally draws attention to the dynamic balance which détermines 

 the living conditions in the aquatic habitats studied and, to the disappearance 

 of the latter when the peat bog will have attained the ultimate évolution of 

 its végétation, i.e. when it will be covered by a forest of mountain pine 

 (climax stage). 



BIBLIOGRAPHIE 



*Aguesse, P. C. 1968. Les Odonates de l'Europe occidentale, du Nord de l'Afrique et des 



îles Atlantiques. Faune de l'Europe et du Bassin méditerranéen. Vol. 4. 



Masson & C ie , Paris. 258 pp. 

 Amann, J. 1928. Bryogéographie de la Suisse. Matériaux pour la Flore cryptogamique 



suisse. Vol. 6. Fasc. 2. Zurich, 453 pp. 

 *Aubert, J. 1959. Plecoptera. Insecta Helvetica (Fauna). La Concorde, Lausanne, 140 pp. 

 *Balfour-Brown, F. 1940. British water beetles. Vol. 1. The Ray Society, London, 



375 pp. 



1950. British water beetles. Vol. 2. The Ray Society, London, 394 pp. 

 — 1958. British water beetles. Vol. 3. The Ray Society, London, 210 pp. 

 Beaumont, J. de. 1941. Les Odonates de la Suisse romande. Bull. Soc. vaud. Sci. nat. 

 61: 441-450. 



Principales faunes utilisées- 



