2o8 



KNOWLEDGE & SCIENTIFIC NEWS. 



[Sspt., 1904. 



Terrifying Ma^sks acrvd 

 WoLrnirvg Liveries. 



By rEKcv Collins. 



It has been suggested — and the theory lias received, to 

 some extent, the support of experimental proof — that cer- 

 tain kinds of insects derive protection from the grotesque- 

 ness or hideousness of their appearance. An oft-cited 

 example is the very remarkable-looking caterpillar of 

 Stauvopus fani, the lobster moth. This insect was at one 

 time considered a great rarity in England, and as such 

 was much prized by collectors. Of recent years, how- 

 ever, it has been found in considerable numbers in the 

 beech woods of the Upper Thames valley, and entomolo- 

 gists have had ample opportunity to examine its appear- 

 ance and habits in the wild state. 



Professor Poulton describes the resting caterpillar as 

 possessing a considerable resemblance to a withered leaf 

 irregularly curled up — the likeness being gained by the 

 combined effect of the creature's colour, its curiously 

 modified legs, and the manner in which these are 

 arranged. 



It is clear, therefore, that this remarkable larva is con- 



Larva of Vh,uro,;,miin I'ornllus, in terrifying attitude (drawn from lifel. 



cealed from its enemies by a protective likeness to its 

 habitual surroundings. But it has yet another means of 

 defence at its disposal. Should it be disturbed by a rust- 

 ling of the leaves and twigs in its immediate neighbour- 

 hood, and become convinced that its disguise has been 

 penetrated, it immediately assumes what has been called 

 its " terrifying attitude." 



In this position it is described as looking very like a 

 large spider, but with all the characteristic points in a 

 spider's appearance greatly exaggerated for the sake of 

 effect. The legs and body are, for the time being, 

 arranged in such a manner that the creature seems 

 changed from a harmless caterpillar into something 

 strangely disquieting to look upon. 



In thus mimicking the attitude and appearance of an 

 exaggerated spider, the lobster moth caterpillar is really 

 trading upon the reputation of a well-recognised noxious 

 creature ; and the defence has been shown by experiment 

 to be of no little avail against the attacks of birds and 

 other insect-eating creatures, which exhibit varying 

 degrees ofalarm and disgust at sight of the caterpillar in its 

 terrifying attitude. But, as several observers have pointed 

 out, it is more than likely that the spider-like appear- 

 ance exists mainly as a special safeguard against the insect 

 enemies of Staiiivpiis fagi. In conmion with the larvx of 

 tnost Lepidopterous insects, this caterpillar is liable to 



the attacks of ichneumon flies, which deposit their eggs 

 upon or beneath its skin. In the majority of instances such 

 " stung " larv.-E die miserably ere they are able to assume 

 the imago state ; and it is only reasonable to assume that 

 any trick or device calculated to scare away these insect 

 foes would directly benefit the species by enabling a 



Larva of Chat'iucawpa (//lein'r, showing "eye spots" on fourth and fifth 

 segments of body. 



greater number of its caterpillars to arrive at maturity. 

 And as a large and presumaijly ferocious spider is a vision 

 of dread to all the lesser denizens of the insect world, the 

 lobster moth caterpillar's terrifying mask is probably very 

 effective. 



Aldus sp. Central America. As it appears when running; and v\hen, 



under the stimulus of alarm, it has drawn its legs and 



antenna; beneath its body. 



Similar instances of what looks like trading upon the 

 reputation of some well-known noxious creature occur 

 among insects, and in some instances the prototype 

 ieems to belong to some widely difl^erent group of living 

 creatures. Thus, a South American caterpillar mentioned 

 by Mr. Bates startled everyone to whom it was shown 



