6()0 C. B. HAKDENBERG. 



which develops when the larva has stopped feeding and is 

 ready to enter the pre-pupal and pupal stages. 



The first act of the young bagworm, after its dispersal has 

 been accomplished and its meandering instinct has been 

 satisfied, is to construct a bag for concealment. This bag i& 

 at first conical, widest at the head end of the larva, and 

 during the first days of the first instar it is carried upwards, 

 while the caterpillar feeds on the upper surface of the leaf. 

 Within a few days it starts feeding on the underside, and the 

 bag hangs downwards, the larva, when moving, crawling 

 along the under surface of the twig or branch. In both these 

 positions the abdomen is deflected dorsad at its juncture 

 with the thorax, the entire weight being carried by the 

 thoracic legs alone. The abdominal and anal prolegs are 

 not used in locomotion, and are probably only brought inta 

 play in so far as they hook into the silk lining of the bag and 

 prevent this from slipping off, or the larva from being dis- 

 lodged by a sudden jerk. When a full-grown larva is removed 

 from its bag and put back on the tree it then also only uses- 

 its thoracic legs in locomotion, and moves with a pronounced 

 dorso-flexion of the abdomen, and along the underside of the 

 branches. Even when placed on a flat surface it does not 

 crawd in a straight line, using both thoracic and abdominal 

 prolegs, but moves on its thoracic legs only, the abdomen 

 being held bent upwards and its caudal part curved ventrad. 

 While it would not be possible for the abdominal prolegs to 

 grasp a small twig between them, as they are very short and 

 rather widely separated so that their hook-bearing surfaces 

 could not be sufficiently approximated, it is clear, from its 

 method of locomotion on a horizontal surface, that the larva 

 has lost through disuse the power of co-ordination in respect 

 to these organs. The points of the hooks are directed out- 

 wards, so that, when the planta is pushed out, these hooks are 

 spread and hook into the silk of the surface against which the 

 sole is pressed. The points of these hooks are extremely long 

 and sharp. 



The bag, as stated, is at first conical and just roomy enough, 



