{72}alike, the only differences observable being in the length of the perpendicular shaft and the direction of the horizontal burrow, which is sometimes curved. These variations are usually caused by the presence of other tunnels in the tree, which the larva invariably avoids, although how it can ascertain that it is approaching another tunnel before actually reaching it, is hard to understand. As development progresses in the pupa, it becomes darker in colour, especially on the wing-cases, which in some individuals show the future black markings of the moth, as early as two months before emergence. Others remain quite white and soft, the green wings suddenly appearing through their cases a fortnight or three weeks prior to the bursting forth of the imago. Previous to this change the pupa works its way up the vertical tunnel, lifts the trap-door, which yields to the slightest pressure from within, and wriggles along the horizontal burrow until it reaches the air, the last three or four segments only remaining in the tree. The thoracic shield then ruptures, and the moth crawls out and expands its wings in the ordinary way, resting on the trunk of the tree until they are of sufficient strength and hardness for flight. The perfect insect, although it must be common, is very rarely seen. It is best reared from the pupæ, which can be often successfully cut out of their burrows and kept amongst damp moss until they emerge. It appears to be much persecuted by birds, as we often observe its large green wings lying about on the ground.[16] The curious "vegetable caterpillar," which is usually referred to this species, probably belongs to one of the larger subterranean larvæ of the family. {73}Family BOMBYCIDÆ. _Nyctemera annulata_ (Plate IX., fig. 3 [M], 3a larva, 3b pupa).