PROTECTIVE COLORATION AND DEFENSIVE STRUCTURES OE LARV.E. 91 



Poulton describes certain terrifying marks as existing upon the 1st 

 abdominal segment of Aglia tau, and placed above the white spiracnlar 

 line. It consists of a white area, enclosing a dark reddish patch, 

 usually slightly invaginated, and, therefore, hidden during rest behind 

 the lobed upper margin of the sub-spiracular line. When the larva is 

 irritated, increased contraction of the body walls produces greater 

 pressure upon the fluid contents of the body, and unfolds the shallow 

 pouch-like invagination behind the lobes, thus exposing a greater 

 surface of the white area, and rendering the dark centre visible. 

 Weismann has shown that the origin of the terrifying marks in the 

 larvae of Choerocampa elpenor and C. porcellus is very similar, the 

 differences largely following from the arrangement by which the eye- 

 like marks are concealed in the former species, except when they are 

 actually needed. In the larva of Stauropus fagi, Miiller discovered, on 

 the 1st and 2nd abdominal segments, below, and rather behind, the 

 spiracles, a shallow pouch-like involution of an intensely black colour, 

 each black area being entirely concealed by a triangular flap, growing 

 from the lower margin of the area, and directed upwards. When the 

 larva is irritated, the flap is depressed, the pouch-like structure is 

 partly everted, and the black patches become visible. Miiller thinks 

 that the patches are intended to imitate ichneumon stings; Poulton, 

 that they may represent a clot of blood derived from a wound inflicted 

 by a parasitic enemy. It is suggested by both observers that the exposure 

 of these tends to shoAv that the larva is already occupied by a parasite. 



Among the American lepidopterous larvae, the brightly hued cater- 

 pillar of Symmerista albifrons is provided with a showy, coral-red hump, 

 and with bright black and red bands on a shining glistening skin, 

 which Packard considers may be interpreted as danger signals to 

 birds, to whom the caterpillar is distasteful. The same observer calls 

 attention to the great dorsal spines, which run entirely along the body 

 of the larva of Schizura concinna, as well as the large lateral spines, 

 which bear some resemblance to elongated hobnails. These probably 

 render the creature very distasteful and repulsive to birds, and less 

 open to attack from parasitic insects. Packard says that we have in 

 the larva of this species a system of conspicuous markings and 

 noticeable appendages, which all result in giving warning to birds that 

 it is inedible .... In the larvae of other Schizurae, we have a mix- 

 ture of two properties ; they are, as we have shown, disguised to re- 

 semble a part of a brown-spotted green leaf, and they also bear a 

 movable, deterrent spine on the back. In Symmerista, the larva is so 

 gaily coloured as to at once indicate to birds that it is distasteful, but 

 here are no deterrent spines or bristles. Edwards notices that he once 

 observed the gregarious larva? of Symmerista albifrons feeding on dwarf 

 willow, where their brilliant colours gave to the plant, at a little dis- 

 tance, the appearance of a raceme of showy flowers. Packard thinks 

 that the habit of feeding exposed, and living gregariously up to the 

 time of pupation, proves the almost complete immunity enjoyed by 

 this caterpillar from the attacks of birds. 



An observation, very similar to that just recorded as made by 

 Edwards, is noticed by Niceville, who says {Butterflies of Sumatra, 

 p. 401) that on one occasion, when Martin was collecting the larvss of 

 Cethosia logani on a passion-flower with red fruit, the latter noticed 

 the protective position assumed by some of the caterpillars, which, in 



