234 THE COURTSHIP OF ANIMALS 



fulfil their reproductive functions and die — in an ice- 

 chamber ! The males have wings which are rarely or 

 never unfurled; as a rule they present nothing more than 

 a crumpled mass of gauzy tissue, as if glued together. 

 Such species as attain to flight are most indifferent 

 performers, travelling but slowly, with laboured move- 

 ments and settling after a f.w yards have been traversed. 



As a rule, among insects, where there is a difference in 

 the power of flight, it is the male which is superior. The 

 case of Nemoura, just referred to, affords an instance 

 where the contrary is the case, and Mr. J. J. Lister records 

 the case of one of these flies — Isogenus nubecula — taken 

 at Loch Tanna in Arran, wherein the wings of the female 

 were greatly reduced, while those of the male were 

 so much so as to be mere useless vestiges. Similar 

 facts have been recorded of more than one species in 

 Scotland, but in all such cases the phenomenon seems 

 to be associated with the appearance of the insect in 

 very early spring. In another species — Nemoura tri- 

 fasciata — only the front wings are reduced, the hind 

 pair being large enough to cover the body. In male 

 specimens of Perla maxima taken in Scotland, the wings 

 are so short as to be useless for the purposes of flight, yet, 

 in the same species taken in Central Europe, they are of 

 ample proportions. 



These facts are puzzling indeed, but they seem to show 

 that flight is not essential to attain the ends of repro- 

 duction. As to whether these flies secure their mates 

 by any kind of " courtship," or how they find one another, 

 seems not to be known. But the female is remarkable 

 for the fact that she carries her eggs about with her, 

 to the number of five or six thousand, attached to the 

 end of the abdomen. 



