THE CAUSE OF MIMETIC RESEMBLANCE. 573 



logical explanation of the facts, in the sense that it is quite con- 

 ceivable that the observed results might be thus obtained. Hence 

 the objection to sexual selection as a suggested cause is not as 

 strong as the objection to the other causes which have bean 

 brought forward. Nevertheless, I believe that very few will be 

 found to support the former suggestion. 



The conclusions here arrived at by a consideration of the facts 

 presented by the Lepidoptera are entirely confirmed by those 

 already known in the Coleoptera ; although as yet but little 

 attention has been paid to the latter Order in this respect. 

 Mr. C. J. G-ahan, in an interesting paper (Trans. Ent. Soc. Lond. 

 1891, pp. 367-374), clearly shows that the Phytophagous genus 

 Diahrotica is in the same position as the large protected groups 

 of butterflies already mentioned {Danaince, Ithomiinee, Helico- 

 nincB, AcrceincB). The indiviiluals of its species swarm in the 

 localities where they occur ; they are conspicuously coloured, and 

 many of them are known to feign death when captured and to 

 discharge a yellow fluid from various parts. The facts at present 

 ascertained justify the conclusion that these Coleoptera form 

 centres of Miillerian resembhmce, in that " some of the species 

 belonging to one section in this genus are, in colour and marking, 

 extremely like certain species of the other section which come 

 from the same localities " (I. c. p. 372). Mr. Jacoby has also 

 " recorded that many of the species of his genus NeohroUca 

 exhibit most striking resemblances to species of the closely 

 related genus Diahrotica.'''' The latter species are also mimicked 

 by those of the allied genus Dircema. Mr. Grahau shows, 

 furthermore, that 18 species of the genus Lema^ belonging to a 

 different sub-family, closely resemble the species of Diahrotica (in 

 one case the allied genus Gerotoma) found in the same localities 

 in tropical America. In three cases species of Neohrotica, and in 

 one a species of Dircema, fall into the groups thus formed. 



Mr. Gahan is disposed to regard the resemblance of the 

 species of Lema, together with that of the Longicorn Oxy- 

 lymma gihhicollis, for a species of Diahrotica, as an example of 

 Batesian mimicry. Future observation and experiment must 

 decide upon this as upon so many other cases concerning which 

 we are uncertain whether to adopt the Batesian or the Miillerian 

 interpretation. Tlie tendency of recent observation, however, 

 strongly favours the opinion that the latter theory will explain 

 a much larger number of resemblances than the former. 



LINN. JOUKN. — ZOOLOGY, VOL. XSVl. 41 



