of the Amazon Valley. 221 



In the last of these families, the Nymphalidoc, there are certain 

 genera and species which exhibit a still further degree of atrophy 

 of the fore legs than that indicated in the description, and prevailing 

 in the majority of the species ; but this extreme point of imperfec- 

 tion is not common to definite series of genera, and therefore is not 

 of any great systematic value. It shows, however, a tendency to 

 further advance in the direction winch we have seen indicated in the 

 successive families ; and the genera which furnish such instances 

 must be considered as exhibiting the highest development of the 

 type of the family, and as being the farthest removed from the 

 division Heterocera. These genera, however, belong to subfamilies 

 widely different in many respects, and placed far apart in the re- 

 ceived classifications, but which agree in the wing-cells being 

 closed by perfect nervules. The nature of the atrophy is not, how- 

 ever, the same in both. Thus, in the Heliconinae several genera 

 have in the J the fore tibia? rudimentary, the tarsi having entirely 

 disappeared ; in one genus (Sa'is) the femora also are much reduced 

 in size. The fore legs of the 5 are in the same insects very slender 

 and feeble, but exhibit all the articulations, except in some species 

 where the fifth appears to be wanting ; they cannot be said, however, 

 to be more rudimentary than in the typical Nymphalidae. On the 

 other hand, in the Satyrinae there are many species, but probably not 

 whole genera, which have the fore legs extremely reduced in both 

 sexes. In Lymanopoda they are very short, weak, and similar in 

 appearance in the males and females ; and in several species of 

 Satyrus the tarsi in the female are jointed, but are deprived of spines 

 at the end of the articulations, and are similar in clothing to those 

 of the males. In Ccero'is the fore legs of the males are of the same 

 rudimentary structure as that of the Heliconina? above mentioned ; 

 thus, in the Satyridse there are some species in which the females 

 as well as the males show a great degree of atrophy of the organs in 

 question, and in others the males only. 



The atrophy of the fore legs in large numbers of the Diurna is no 

 new fact in Lepidopterology ; it was known to the earliest writers on 

 the order ; but the difference of structure according to sex remained 

 long undiscovered. No application or mention is made of it, except 

 with regard to the Erycinidse by Dr. Boisduval in his ' Species 

 General,' published in 1836. The order, in fact, has not generally 

 had the advantage of being studied in a scientific spirit. A precon- 

 ceived notion seems to have prevailed that no important characters 

 were to be derived from the structure of the adult insects. Latreille 

 called the order " the stumbling-block of entomologists.'' The 



