PSYCHE. 



CONVERGENCE AND POECILOGONY AMONG INSECTS. 



BY ALFRED GIAHD, PARIS, P'RANCE. 



[Professor Alfrt-d Giard in tlie An- 

 nals of tlie Entomological Society of 

 France* presents a careful discussion of 

 convergence and poecilogon}' among 

 insects and a resume in the form of a 

 rather free translation may be of interest 

 to some who do not have access to this 

 publication. Herbert Osborn.] 



It is a well known fact to entomolo- 

 gists that certain insects which are 

 very similar to each other in the adult 

 state have larvae which are quite 

 different. Many examples of this 

 peculiarity have been indicated, princi- 

 pally among the Lepidoptera, the 

 larvae of which are better known than 

 those of other groups. But all insects 

 with complete metamorphoses may 

 present the same phenomena, and, if 

 it is more rare among the ametabola, 

 it is because, among these, the passage 

 from the larval to the adult stage is 

 gradual, by insensible steps, and the 

 larvae and imago are subject to much 

 the same conditions. One of the cjues- 

 tions of much importance and at the 

 same time a problem of much difficulty 

 to solve is to determine if. in tiie recog- 

 nition of the agreement between similar 

 animals which present differences in 



* Vol. 63, pp. 128-135. 



the earlier stages, we should attach 

 more importance to the early dissimil- 

 arity than to the similarities of the 

 adults. The question would be 

 answered immediately in the affirma- 

 tive if the principal of Fritz Mueller, 

 the fundamental biogenetic law of 

 Serres and Haeckel, were applicable 

 in its exactitude. Tiiat is to sav, if 

 the various ontogenetic states of an 

 animal repeated exactly the phylogeny 

 or the successive ancestral forms. 

 Were this so, embryology would indi- 

 cate the true relation of the parents. 



The more or less perfect resemblance 

 of the adults in certain cases would be 

 interpreted as the result of convergence 

 due to similar etliolog\' of these adult 

 forms. But, among animals with 

 metamorphosis, embrvonic forms are 

 subject during a long period to the 

 modifying action of the surroundings 

 and often, also, their evolution depends 

 in a large measure upon the ethology 

 of the adult. Accordingly, the prin- 

 ciple of Fritz Mueller is applied with 

 difficulty and singularly tliough actually 

 the determination of the relation of the 

 parents becomes more arduous the 

 better we know the different phases of 

 development. If it he true that partial 

 knowledge happens thus to complicate 



