328 Mr. Poulton's/iwi/ier 7iotes upon the 



disappeared from the tubercles, which are now only distinguished 

 from the others by their greater size. In these three figures there 

 is traced the gradual disappearance of a structure which must 

 have been very conspicuous, from its colour and position, when it 

 reached its culmination in the fifth stage. Its present significance 

 appears to be historic. This seems to support the argument that 

 the Smerinthus larva was brightly coloured, but has undergone 

 alterations for protective purposes. The brightly-colom'ed spots 

 that often appear on the body of Smerinthus larvis are explained 

 as due to reversion by this theory. 



Fig. 15, x 6 diam. — The larva of Selenia illunarla just after 

 emergence from the egg, seen from the left side. The figure 

 represents the habitual attitude of rest at this stage. The body is 

 almost black, thinly covered with hairs (not shown), and encircled 

 by four white interrupted bands. 



Fig. 16, x 2 diam. — The larva of S. illwnaria towards the 

 beginning of the second stage, seen fi-om above. The ground 

 colour is not so dark, the anterior band is distinct, the others much 

 less so ; the posterior band has become broad, and has spread 

 backwards over the 5th abdominal segment as a light greyish 

 cloud. The ground colour is still dark brown, becoming dull 

 black posteriorly, but there is much variability. The protection at 

 this stage is due to a resemblance to the excrement of birds, 

 which is much assisted by the irregular (sometimes) asymmetrical 

 attitude. 



Fig. 17, natural size. — The larva of S. illunaria in the third 

 stage, seen from the right side, at rest in the protective attitude. 

 The appearance is now much altered. The anterior band is visible 

 as two transverse pale yellow marks on the dorsal surface of the 

 anterior part of the 2nd abdominal segment. The last band is also 

 present as a light cloud upon the sides of the 4th and 5th abdo- 

 minal segments, which are swollen, and each of them has two 

 tubercles on the back. The ground colour consists of various 

 shades of brown, or sometimes of dull yellow. The last pair of 

 thoracic legs are placed on a prominent transverse ridge projecting 

 from the ventral surface of the 3rd thoracic segment. By holding 

 the ridge and the legs, as shown in the figure, the bend in the 3rd 

 thoracic segment is made to appear exceedingly angular. The 

 head is very flattened, and continues the line of the two anterior 

 thoracic segments, and, like them, it is lighter on the under 

 surface. The 1st and 2nd pairs of thoracic legs are bent upwards, and 

 are thus inconspicuous. There are also other bends in the body of 

 the larva, as shown in the figure. The very irregular attitude is 

 assumed upon the surface of the leaves of the food-plant, for the 

 larva does not at this time retire to rest upon the twigs. Hence 



