1 06 A BIOLOGY OF CRUSTACEA 



so helps to keep the nest clean, hut it also supplements its diet with 

 the sugary excrement of aphids which ants often keep in their 

 nests. Pregnant females spread the species from nest to nest; they 

 leave the nests at night and wander ahout; as daylight approaches 

 they take cover again and are attracted towards ant nests hy a 

 positive reaction to the formic acid which ants produce. 



This is a clear-cut example of a species responding to a particular 

 chemical suhstance produced hy the animals with which it 

 associates. It is likely that many of the other more specific associa- 

 tions described above involve reactions to substances produced by 

 the associates, but the substances are likely to be more complicated 

 than the formic acid of ants. 



LITERATURE 



Borg, F. (1935). Zur Kenntnis der Cladoceran Gattung Anchis- 



tropus. Zool. Bidr. Uppsala. 15: 289-330. 

 Caullery, M. (1952). Parasitism and Symbiosis. London. 

 Dales, R.P. (1957). Commensalism. In: Treatise on marine ecology 



and palaeoecology. Geol. Soc. Amer. Mem. 67, Vol. 1. pp. 391- 



412. 

 Gotto, R. V. (1957). The biology of a commensal copepod, Ascidi- 



cola rosea Thorell, in the ascidian Corella parallelo gramma 



(Muller). /. mar. biol. Ass. U.K. 36: 281-290. 

 Green, J. (1957). Parasites and epibionts of Cladocera in rock pools 



of the Tvarminne Archipelago. Arch. Soc. zool.-bot. fenn. 



Vanamo. 12 : 5-12. 

 Mathes, I., & Strouhal, H. (1954). Zur Okologie und Biologie der 



Ameisenassel Platyarthrus hoffmannseggii. Z. Morph. Okol. 



Tiere. 43 : 82-93. 

 Viaud, G. (1947). Recherches experimentales sur les tropismes des 



rotiferes. L'oscillorheotropisme de Brachionus rubens Ehren- 



berg, cause de la fixation de ce rotifere phoretique sur les 



daphnie et autre crustaces d'eau douce. Ann. Sci. nat. Zool. Fr. 



(11)9: 39-62. 



