512 INTERACTION OF ENDEMIC 



Recorded cases of increase among other groups of indigenous 

 animals other than birds, are very few. 



The two moths, whose larvas are known as "flax-grubs" — Xan- 

 thorhoe prcefectata and Melanchra steropastis — are both considered to 

 be much more abundant now than they were formerly. It may be 

 that by the clearing away of other native vegetation on which they 

 formerly fed, their attacks are now made more persistently on flax- 

 covered areas, but the pest has assumed such serious proportions in 

 recent years, as to lead to combined efforts to cope with it. 



Another native moth — CEceticus omnivorm — appears to have in- 

 creased also to a considerable extent. Within the last few years also 

 very many complaints have been received of the steady increase of 

 a moth Venusia verriculata, whose larva feeds on and occasionally 

 nearly destroys the cabbage-tree {Cordyline australis). 



The common magpie-moth {Nyctemera annulata) has certainly 

 become extremely abundant wherever the introduced ragwort {Senecio 

 jacobcea) has become a common pest. Formerly Nyctemera appears 

 to have fed chiefly on the indigenous Senecio bellidioides, S. Lautus 

 and glabrous species of Erechtites, but it has transferred its atten- 

 tion now chiefly to the introduced species of Senecio (including 

 S. vulgaris and S. mikanoides). Wherever ragwort has spread and 

 become an abundant weed the Nyctemera has also increased enor- 

 mously, and may be seen rising in vast swarms from the plants during 

 the adult moth stage. I have never seen a bird catching the moths, 

 and the hairy caterpillars appear to be very distasteful to them. I know 

 chickens will not touch them. Hence they seem to increase almost 

 without check from enemies. The only bird I have heard of as eating 

 them is the shining cuckoo (Chalcococcyx lucidus); my informant is 

 Mr Holman, Curator of the Whangarei Acclimatisation Society, who 

 is a careful observer. 



It is difficult to get any information as to changes in the abundance 

 of native insects due to the introduction of foreign species of plants. 

 One species of beetle, Odontria zealandica, the common "grass- 

 grub," has apparently greatly increased with the introduction and 

 increase of European grasses. It is extraordinarily abundant in some 

 pastures, and is most destructive to lawns. Two allied species, O. punc- 

 ticollis and O. striata, have been found to be very destructive to seed- 

 Kng trees in the State nurseries. The former is most active in the 

 North Island, destroying sometimes as much as 30 to 40 per cent, 

 of the seedling larch [Larix Europaa). O. striata is most in evidence 

 in the South Island, where it destroys both larch and Pinus laricio. 

 The common longicorn beetle — Prionoplus reticularis — cannot be at all 

 so common as it was before the wholesale destruction of forest trees 



