264 Transactions. 



on these points. From my experiments it appears that their sight is poor, 

 and that the larvae are influenced more by large objects, even at a distance, 

 than by much smaller and closer things. Larvae placed in the open on 

 bare ground were seemingly attracted by high trees in the immediate neigh- 

 bourhood, but failed to observe or direct their way to small food plants and 

 other objects of 2 in. or 3 in. in height placed within a few inches of their 

 path ; tney even seemed quite unaware of such objects placed right in 

 their way till the long hairs of the thoracic segments, which project out over 

 the head, came in contact with them. This seems rather curious, since a 

 larva will frequently, while crawling on the ground or elsewhere, halt and 

 rear the head as high as possible, as though to take a very comprehensive 

 view of all the surroundings. When they are travelling in the open they 

 always appear to have some definite object in view, and to be going straight 

 to it. and it generally needs an insurmountable obstacle to force them to 

 make a definite change of direction. Larvae crawling over large sheets of 

 cardboard would more or less change their course on the sheet being turned, 

 though they would rarely hit exactly on their original direction ; but many 

 more experiments are necessary. Regarding sound and hearing, it seems as 

 though this larva were quite deaf ; apparently no amount of noise produces 

 the slightest effect, yet it is appreciable of the minutest vibration imparted 

 to the object on which it may be feeding. 



During the summer months they are often to be found crawling over 

 the paths, and can travel at a fair speed ; one that was timed traversed 

 4 ft. in a minute. T am told by several reliable authorities that these larvae 

 are a serious pest to cereal crops, and a few years ago caused a great amount 

 of devastation in the Wangaehu district, ruining field after field of oats : 

 on one occasion numbers of them crossing the railway-line on a steep grade 

 from one field to another caused the stoppage of the express.* 



Prior to moulting, the body becomes dark in colour, and the hairs of 

 the coming instar — or, rather, of the new skin- can be plainly seen. The 

 larva seeks a secluded position on the underside of a leaf, and will spin a 

 light silken carpet in which to firmly wedge the crochets of the prolegs. 

 It seems as though this habit of carpet-laying is not acquired till after the 

 third moult. The anterior portion of the prothorax gets greatly extended, 

 and on the sides the eyes of the new head can be distinguished under the 

 overlying layer of skin ; the new mandibles can be seen occupying the 

 cheek-spaces of the old head. These characteristics are peculiar to the 

 period just prior to the moult in all lepidopterous larvae. Actual moulting 

 operations are exactly similar to those of P. ckalcites. The true legs through- 

 out the operation are held close to the leaf, but are not fixed on it in any 

 way. The skin eventually breaks behind the head, and is gradually worked 

 back off the body, the last few abdominal segments, however, being pulled 

 out by the larva itself. During the next hour or two it will remain quiet, 

 occasionally making convulsive movements in order to expedite the drying 

 and setting of the setae. The actual process of moulting may occupy only 

 a minute or less. 



The Imago. — The imago is diurnal, and is a rather lazy flyer, except 

 during the early hours of the morning soon after sunrise and in the early 

 evening, when it may be seen flying very high and around the tops of the 



* Since writing the above I have communicated with Mr. G. V. Hudson on this 

 subject. He says he has never heard of the larva feeding on oats. Probably my 

 informants may have made a mistake in identity. 



