December, 1912.] 273 



Nyssia lapponaria. — Appears in April and May in Perthshire, Scotland; 

 food-plant .- heather, bog myrtle, will also eat birch, sallow, and hawthorn. 

 The moth is very local, frequenting damp places near streams. (South.) 



Nyssia zonaria. — Appears in March and April ; food-plant : sallow, dande- 

 lion, dock, plantain, clover, yarrow, grass, etc. The moth rests by day on or 

 among herbage. The male has been known to fly in the sunshine, but its more 

 usiial time of flight is the early evening, (South.) 



With the few exceptions shortly to be specified, it will be seen that 

 a striking agreement exists between the New Zealand and the British 

 species in the following respects : — 



(1) General Distribution of the Food-Plant of the Larva 

 IN THE Region where the Insect is Found. 



There is no exception to this rule, which holds good in evexy case 

 where the female is semi-apterous and the food-plant is known. It is, 

 in fact, obvious that the semi-apterous state would be absolutely fatal 

 to an insect feeding on a scarce or local plant, as the females would 

 require to travel over extensive areas in order to deposit their eggs. 

 Any advantage which a species might obtain by possessing a semi- 

 apterous female would therefore be wholly neutralized unless its food- 

 plant were very common and generally distributed. 



(2 J Appearance of the Imago in Winter or in 

 Very Early Spring. 



It is in this circumstance, which is common to all the species 

 having semi-apterous females, with the exception of the three species 

 of Metacrias in New Zealand, and the two species of Orgyia in the 

 British Isles, that in my opinion an explanation of the semi-apterous 

 condition of the female is to be sought. As a matter of fact, 

 M. erichrysa and M. Jmttonii can hardly be regarded as exceptions seeing 

 that they are both strictly alpine insects, and therefore practically exist 

 under winter conditions. One of the species of Orgyia also occasionally 

 appears in winter and may therefore have recently changed its habits. 

 The only important exceptions are therefore M. strategica (New Zealand) 

 and 0. antiqua (Britain), and of the latter insect there appears to be a 

 succession of broods throughout the entire summer. As corroborative 

 evidence from insects belonging to an order other than the Lepidoptera, 

 two of our common Crane-flies, Tipula nhscuripennis and T. heterogama, 

 occur to me. They have semi-apterous females and appear often in 

 considerable numbers late in April and during May, a period which 

 must, of course, be regarded as winter in New Zealand, I think, 



