xc MIMICRY IN SILK-WORM MOTHS. 



It may be objected that the colours of these moths are very diflferent from 

 those of the cobra and other snakes, but allowance should be made for the 

 moths resting under the shade of leaves, as they would often be, during 

 the sunny hours of the day, when the colours would not show up so 

 brightly. In such circumstances, well marked colouration would be 

 necessary to bring out the details when in deep shadow, and even the apex 

 of the forewing of such a brightly coloured moth as Loepa hatinka 

 (Westw.) might be mistaken for the head of one of the smaller bright 

 green snakes. In any case, the phenomenon is a most remarkable one, and 

 I have not read as yet of any reasonable explanation of it ; that there is 

 a reason for it is as great a certainty as that there is a reason for the 

 existence of everything in nature, in the economy of which all forms of 

 life work out their allotted duties. Let us try, then, to see how we may 

 reasonably account for it. 



Being of large size, these moths are conspicuous objects, when resting, 

 and some protection is necessary for the continuation of the species. 

 There are in India 213 species of snakes of which some 33 are poisonous : 

 the food of many of them consists of rats, mice and small birds, — a per- 

 centage of which are insectivorous : the toll of birds taken \>j these 

 reptiles must be very considerable, and is said to be obtained by the 

 exercise of a mysterious power termed 'fascination,' the victim being 

 held, as it were, by the gaze of it's destroyer, and compelled to remain in 

 the same spot until the serpent can approach sufftciently near to seize it. 

 It is clear, therefore, that an insectivorous bird in pursuit of a moth 

 amongst the leaves of a tree would be quickly brought to a standstill by 

 the appearance of a snake's head just as it was about to seize it's prey. 



Now an Atlas moth resting amongst the leaves of a tree (as shown in 

 Plate No. I.), with the apices of the forewing projecting and giving the 

 appearance of a snake's head, would, in my opinion, have a good chance of 

 escape from any insectivorous bird, which suddenly came across it ; and as 

 the \ipper and underside of the wings representing the reptile are coloured 

 in a similar manner, the result would be the same on whichever side it was 

 approached. 



Such appears to me to be the most likely explanation of the phenomenon. 

 Some remarks in detail on the forms figiired may now be given. 



Fig. 1. — Attacus atlas Linn — In this form a side view or profile of the 

 snake's head is seen. The eye is represented by the black subapical spot, 

 and the mouth by the crimson streak below it, while the dark markings 

 with whitish edges and diaphanous spot in the centre of the wing would 

 serve to represent the " hood " and " spectacles" of a cobra. 



Fig. 2. — Attacus edivardsi White. — This form gives the most startling 

 and sinister representation of a Serpent's head of any of the forms figured. 

 The aspect presented is that which would appear to an observer looking 

 down on it from above ; the violet subapical patch would represent the 

 shining surface of the top of the snake's head ; the small black subcostal 

 apical spot is the left eye, and the somewhat elongated oval black spot 

 between veins 6 and 7 the right eye, while the mouth and lips are shown 

 by the submarginal and marginal lines ; as in fig. 1 the central markings 

 serve to represent the "hood " and "■ spectacles. " 



Fig. 3. — Attacus mithymna (Westw). — An African form representing a 

 smaller species of snake viewed from above ; the various details are well 

 brought out in this form : central markings present, and give a fair 

 representation of " hood " and " spectacles " of Naja haje, the African 

 cobra. 



Fig. 4. — Attacus cynthia, (Drury) — A form very similar to the last, but 

 nrach lighter in colouration ; snake's eye and mouth well delineated. This 



