RURALIS BETULiE. 299 



Koch, Kretschmer, Schmid, etc.); Betula (Linne); Betula alba (Ochsen- 

 heimer, Stainton, Snellen, Boie, Moschler, Nickerl,Eichter, etc.); cherry, 

 peach (Borkhausen) ; Corylus (Hofner, Paul and Plotz) ; Amygdalus 

 nana cum flore pleno (Richter); oak (Hofner, Crisp); poplar (Hofner); 

 alder (Donovan); buckthorn (Moses Harris). 



Parasites. — Agryponflaveolatum, Grav. (Bignell); Campoplex pugil- 

 lator, Linn. (Eedle); Campoplex eurynotus, Forst. (Eedle). 



Pupation. — When fullfed and ready to pupate the larva changes to 

 a rusty-brown colour. Albin observes that a larva of Ruralis betulae 

 was taken on June 8th, 1720, and tied itself up after the manner of 

 the "white" butterflies, and on July 16th came forth the "hairstreak " 

 butterfly. This was probably the origin of the statement, by Bork- 

 hausen, that the pupa was smooth, round, and blunt, and " fixed the 

 same as the pupa of the cabbage butterfly, brassicae." When fullfed and 

 already of changed colour, the larvae become more active, and often leave 

 the foodplant, roaming restlessly until a suitable position for pupation 

 has been found. This, however, is most frequently, in confinement, a 

 leaf of the foodplant. Careful examination shows that the fullfed larva 

 spins no girth, but forms a very fair silken pad, into which its prolegs, 

 especially the last ventral and anal pairs, are tightly fixed, so that the 

 cast larval skin remains over the anal segments of the pupa, and that 

 this forms the means of attachment of the pupa. A larva was noticed, 

 on July 8th, resting on the underside of one leaf, venter upwards, with 

 another leaf pulled almost over it by means of a few loose threads, 

 sufficient to retain the latter in position, but not sufficient to enclose 

 the larva so as to prevent its being clearly seen on either side. It is 

 resting as if it were supported by a silken girth, but there is no trace 

 of one. Another larva, observed on July 12th, had spun a pad on the 

 top of two plum leaves, so as to join them as a common base ; it had 

 then pulled over, and loosely attached to the leaf, some pieces of dried 

 moss, that cover the dorsum and quite hide the larva, the threads 

 having to be disturbed to inspect the larva. Yet another was observed, on 

 July 12th, 1907, to pull a leaf together with a few silken threads, so as 

 to cover itself, forming a weak sort of cocoon, but the silk threads can 

 be severed without affecting the pupa, which evidently relies solely for 

 support on its attachment to the cast larval skin adherent at the 

 anal end of the pupa. The pupa resulting from this last larva was 

 observed, on July 17th, to have the tail completely buried in the 

 exuviated skin by which it is quite firmly attached, and this attach- 

 ment is sufficient, even when the pupa is on the underside of a leaf, 

 and resting horizontally thereon, dorsum downwards, to keep it in 

 fixed position, but any outside pressure directly applied readily loosened 

 the pupa from its position in the larval skin. Prideaux observes 

 (in litt.) that, previously to pupation, the larva spins a pad of silk, 

 either on the top or sides of the breeding-cage, or, in some cases, inside 

 half-withered leaves of plum. The prolegs are very firmly fixed to the 

 silk pad, a proceeding necessary enough, as this involves the sole 

 means of pupal attachment. The larva spins no sort of silk girdle, 

 the pupal attachment (as mentioned above) being entirely dependent 

 on the larval skin, which is never completely cast, but adheres 

 pretty firmly to the pad of silk by the empty larval prolegs. There 

 are no cremastral hooks ; the dumpy pupa can neither be said to 

 be suspended, nor is it flush with the surface of the cage or leaf, 



