group of Butterflies, Potaro District, British Guiana, 415 
allied undescribed species. There must be much specula- 
tion as to whether JZ mneme or IZ. crameri commenced to 
draw the many other species to them in coloration and 
pattern. JJelinva mneme is a strong variant in both fore- 
and hind-wings while IZ. crameri is very constant above 
and only as a very rare aberration is a form found with 
the black of the hind-wing divided by the ground colour 
so as to forma band. On the under-side, however, there 
is considerably more variation. The latter species, owing 
to its comparative constancy, must be looked upon as 
older than JZ. mneme, a very variable and apparently 
unstable species. It is however certain that if JZ. cramera 
was first in the field, 1, mneme must have entered soon 
after, for many of the associated species of other genera 
follow JZ. mneme to a greater extent than MZ. cramerv. 
In fact IZ. mneme must have been far more potent than 
M. crameri, and the strong variability must have been a 
great factor in drawing so many different species to the 
association. Of MM. egina there is every reason to suppose 
that it became a fixed and well-defined species early in 
the history of the group, for we find only one other species 
closely following it, and that also is a usually very constant 
species, Heliconius silvana. It should here be mentioned 
however that two specimens of Heliconius have been 
caught, one in March 1905, the other without date, which 
appear to be aberrations of H. silvana with a distinct 
transverse black band to the hind-wing. These un- 
doubtedly point to a not very distant genetic relationship 
with Heliconius numata. 
Unquestionably the closest “pairs” are the Melinwa 
with Heliconius species. Mechanitis follows them very 
closely with Lycorea also. While Hucides, Ceratinia and 
Stalachtis, in the order named, diverge more and more 
from the protected pattern. ‘The identical pattern and 
colour in some of the forms of Heliconius numata to IM. 
mneme is remarkable, as in the Potaro district the Heliconius 
is apparently never abundant, rarely even really common. 
I have only 32 specimens, and this represents the whole 
take. The series is most remarkable for the very ex- 
tensive variation, some having a narrowly barred hind- 
wing, others having almost the whole of the hind-wing 
black except for the costal portion. The Lycoreas are 
certainly more abundant, while the MJechanitis species, 
both pannifera and polymnia, occur in large numbers. Of 
