318 Mr. Poulton's notes in 1886 



Fig. 4. Natural size. A mature larva of Avrvphidasis betularia, 

 seen from the left side. The figure represents a common green 

 variety of this variable larva, and it is seen that in this, the usual 

 attitude of rest, the larva is supported by holding a portion of the 

 food-plant with its last pair of thoracic legs, instead of by the 

 thread which is usually spun by the larvse of Geometrce for this 

 purpose. 



Fig. 5. Natural size. The mature larva of Bmnia cratcegata, 

 as seen from the right side attached to its food-plant — hawthorn— 

 in the natural attitude of rest. The larva is recognised by the 

 supporting thread, which, however, from its colour and fineness, 

 does not attract attention in nature. The figure was drawn from 

 an actual specimen of the larva on its food-plant, and it indicates 

 the remarkable resemblance between the structural details of the 

 animal and the plant upon which it most commonly occurs. The 

 twigs resemble the larva in colour, in shape, and in direction. 

 About in the middle of the majority of the twigs there is a 

 prominent projection, which is almost exactly imitated by the 

 dorsal tubercles of the larva ; the processes form the crown of a 

 very slight bend in both, while the ends of the twigs greatly 

 resemble the head of the larva. Such a specialised protective 

 resemblance would seem to be the product of a very prolonged 

 association of the larva with this species of plant. 



Fig. 6. Natural size. The mature larva of Dicranura vinula in 

 the terrifying attitude, as seen from the left side. The larva had been 

 irritated on the left side of its body, and, in obedience to the tactile 

 stimulus, had assumed the attitude represented in the figure. In 

 addition to the terrifying appearance being thus brought to bear 

 upon the point from which the attack is made, the mouth of the 

 gland secreting formic acid is also directed so that an enemy 

 would probably be struck by the discharged fluid. The caudal 

 flagella are represented as everted to their full extent, although 

 the power of using these weapons is generally lost in the mature 

 larvae. 



Fig. 7, X 2 diameters. The head and prothorax of a larva of 

 Dicranura vinula towards the beginning of the last stage, looked 

 at from below. At this stage of growth slight pressure applied to 

 the larva causes the eversion of the gland-tubes which secrete the 

 formic acid, and of the median sac in which the fluid is stored. 

 There are seen to be four tube?, the anterior pair being longer and 

 wider than the posterior pair. The position of the everted organs 

 is seen to correspond with that of the horizontal slit-like mouth 

 through which eversion takes place, and shown upon the red 

 margin of the prothorax below the head in fig. 6. 



