Ajsttjrida. 481 



tion lias been made to account for the frequent occurrence 

 of wingless insects on oceanic islands. Among the few 

 insects, for instance, known from Kerguelen Land there 

 are three species of flies whose wings are atrophied, in 

 one instance they have gone altogther, and in the other 

 two cases they are reduced to mere scale-like appendages. 



Marine Diptera are principally met with flying over 

 the masses of Fuci east up by the tide on the shore ; some 

 few, however, may be seen skimming lightly over the 

 surface of the water in the tide-pools. Most of the larvae 

 of these flies feed on thrown-up Fucus and are covered at 

 each tide, but those of the Chironomidse are submerged 

 during the whole course of their life, and subsist on 

 Cladophora and other green Algse growing in the pools 

 left among the rocks by the receding tide and, further- 

 more, they have also been dredged up from a depth of 

 over ten fathoms. 



The following British Diptera are all marine: — 



Fucellia fucorum (Fall). Aphrosylus raptor, Halid. 



Coelopa frigida, Meig. A.ferox, Halid. 



Orgyma luctosa, Meig. Thalassomyia Frauen- 

 Actora aestmmi, Meig. feldii, Schiner. 



Glenanthe ripicola, Halid. Chironomiis sp. ? 



Chersodromia arenarm, Clunio marinus, Halid. 



Halid. Clunio bicolor, Kieft". 



Hemiptera. 



Aepo philus Bonnairei, Sign. 



The species of Halobates and Halobatoides are 



exclusively marine and inhabit the tropical waters of the 



oceans. They have not been found further northward 



than Spain. 



