Hudson. — Flirpithss Feynales in certain Species of Moth,<. 57 



petuation of the species is concerned, especially if the males outnumbered 

 the females, which is known to be the case in many insects. It may, of 

 course, be urged that a far simpler explanation of the semi-apterous con- 

 dition is to be found in a lowered vitality, induced by cold, preventing the 

 full development of the organs of flight ; but the winged condition of the 

 male, in my opinion, negatives this explanation, and the existence of many 

 winter insects with fully developed wings in both sexes is also against it. 

 Briefly stated, then, I believe that the semi-apterous females have been 

 evolved in many insects appearing in the winter or very early spring 

 because such a condition prevents them from leaving the food plant and 

 being afterwards unable to return to it to deposit their eggs when overcome 

 by the effects of cold. Such insects would naturally feed on widely dis- 

 tributed plants, as otherwise the semi-apterous condition of the female 

 would be a fatal disadvantage ; and this fact is in complete agreement with 

 actual observation. In view of the restricted data on which this theory 

 is based, it is put forward as a provisional hypothesis only, and may, 

 of course, be subject to modification or rejection in the light of more 

 extended investigations. 



As a subsidiary advantage, the ability jpossessed by semi-apterous 

 females to secrete themselves in crevices in the bark or in the ground may 

 be mentioned ; but I do not consider such an advantage would be com- 

 mensurate with the loss of flight, and it cannot therefore, in my opinion, 

 be regarded as the primary cause of the modification. 



In conclusion, I should point out that the extreme abundance of many 

 of the species possessing semi-apterous females indicates that the innovation 

 has proved a most successful one in the struggle for existence, and this is 

 further demonstrated by the fact that almost all the species appear in 

 winter, when the insectivorous birds are often sorely pressed by hunger, 

 and in consequence keenly on the alert for insect food. 



Art. VIII. — Notes on the Entomology of the Ohakune and Waiouru Districts, 



By G. V. Hudson, F.E.S. 



{^Read before the Wellington Philosophical Sociefi/, 1st May, 1912.] 



The following notes on insects observed and captured in the neigh- 

 bourhood of Ohakune and Waiouru are the results of a visit made by 

 myself, wife, and daughter in January last. During the twelve days 

 spent in the locality the weather was, on the whole, favourable for 

 collecting, but a deficiency of brilliant sunshine considerably restricted 

 the appearance of certain species. At Ohakune almost all the collecting 

 was done in the forest, which is very accessible, and traversed by good 

 tracks in several directions. On one of the most favourable days of our 

 visit I managed to make a hurried trip to the lower slopes of Mount 

 Ruapehu, but, owing to the distance which had to be traversed, only 

 about three hours were available for collecting on an area ranging from 

 4,500 ft. to 5,000 ft. above the sea-level. I have seldom visited a moun- 

 tain so barren of insect-life, and, although my stay was necessarily very 

 brief, the weather was perfect, and it therefore seems evident that u\ost 

 of the species characteristic of mountains in the South Island are not 

 found on Ruapehu. 



