14 NATURAL SCIENCE. ^arch 



blance, although striking enough to our eyes, did not deceive the 

 insect, for it was never observed to make any attempts to pair with 

 the bird ; and it is notorious that butterflies are often deluded into 

 believing an insect of a different species to be a suitable mate. If an 

 insect with its limited and imperfect vision is proof against a 

 deception which is enough to strike an observant naturalist, would 

 birds be so ? 



A very singular case of apparent mimicry has not yet been 

 quoted in popular works dealing with this subject. Dr. Bovallius^ 

 has lately described a species of Amphipod Crustacean which he 

 named Mimonectcs on account of its likeness to a Medusa. The body 

 of this animal is produced into a dome-like structure transparent as 

 glass, from the underside of which depend the minute legs, crowded 

 together so as to suggest the tentacles of a Medusa. Here we have a 

 resemblance which is the more striking, inasmuch as it exists between 

 animals widely removed from each other in zoological position. And 

 the poisonous character of the Medusa, armed as it is with innumer- 

 able "lasso cells," would seem to make it an excellent model for the 

 defenceless Crustacean to copy. Furthermore, it is a pelagic animal 

 living in the surface waters just as Medusas do. Nevertheless, it is 

 exceedingly doubtful how far the Mimonectes profits by its departure 

 from the usual plan of structure of the group to which it belongs. A 

 school of whales or a shoal of pelagic fish, rushing through the water 

 open-mouthed and devouring all before them, could hardly be supposed 

 to stop and analyse carefully the advantages or disadvantages of 

 selecting or rejecting a given animal as food. And these must be the 

 chief enemies with which small pelagic creatures have to reckon. 



Another case of mimicry, which would seem to confer no 

 particular advantage on the disguised insect, is noted by Dr. Seitz.3 

 He calls attention to the close similarity between two moths — Brephos 

 nothum and Ploseria diversata — belonging to different families, which 

 emerge from the chrysalis at about the same time. So detailed is the 

 resemblance, that, according to Dr. Seitz, " it would be carrying 

 scepticism too far to regard the agreement as merely the result of 

 accident." This is plausible but not entirely convincing, if we take 

 other facts into account. Mr. Poulton, in arguing for the efficacy of 

 " warning colours " (and of course this will include mimicry), points 

 out " the entire disappearance of all insects with warning colours 

 during the seasons when insect life is scarce," and therefore in great 

 requisition by birds. During the earlier and later months of the year, 

 anything in the shape of an insect will be eagerly snapped up, and 

 warning colours would become a danger signal, not to the bird, but to 

 the insect. Now March is the month in which these two moths 

 appear ; and they are generally the only insects on the wing. They 

 would therefore be an obvious mark for any birds that were about, 



' Nova Acta, R. Soc, Upsalu, 1885. "* Zoologische Jahrbuchey, 1SS9 



