140 :^IR. C. N. BARKER 



mens in the British Museum were sent there as shells. 

 This case is not, like those of other Psychidse, constructed 

 of earth or vegetable matter^ but is of silk and is in tex- 

 ture and appearance exactly like the surface of a shell. 

 Psyche helix is, according to Ingenutzkj, found in great 

 numbers near Lake Issyk-Kul in Central Asia, where the 

 larvae feed, in their snail-shell -like cases, on grass just 

 like snails." Few organisms are more preyed upon than 

 snails, so I quite fail to see of what benefit to the Psychid 

 this wonderful mimicry can be. Some parasitic bees re- 

 semble their hosts, and it might be inferred that the like- 

 ness is to cover their intrusions, but, unfortunately for 

 this hypothesis, there are many other inquilines that do 

 not in the least resemble their hosts, and are by no means 

 incommoded on that account. Some Asilidse mimic bees 

 and wasps upon which they prey, some spiders simulate 

 ants; mantispas (Xeuropterons) copy mantids (Orthop- 

 terons). In the case of all these, close association or 

 similarity of habits appears to directly influence their 

 superficial and even structural characteristics, whether 

 due to psychological or physiological causes, or both, I 

 do not feel competent to determine; but there are no 

 obvious reasons for these resemblances being accounted 

 as the results of natural selection. The analogous pheno- 

 mena occuring between termites and ants, particularly 

 in those extraordinary castes called soldiers, which be- 

 long to groups zoologically so far apart, is another in- 

 stance in nature of like habits producing like results. 

 Sharp infers that these analogies " probably (point) to 

 some similar physiological susceptibilities in the ances- 

 tors, at an extremely remote epoch, of both groups." 

 ^^ Cambridge Natural History — Insects," Part I, page 

 503. The larva? of insects of many distinct orders are 

 remarkably similar according to their modes of life; thus 

 the larvje of Saw-flies (Tenthredinida^) that bore in hard 

 wood of trees are similar in appearance to coleopterous 

 larvae of similar habits, whilst those that feed on leaves 

 resemble lepidopterous larvae that do likewise. 



