4 
W. Doherty — A List of the Butterflies of Eugano. [No. 1, 
formula for the Attidai seems to be 4, 1, 3, 2 ; the fourth pair of legs being 
the longest and the second pair the shortest. In Synageles picata the 
formula, to judge from a figure ( l . c.), is 4, 2, 3, 1. Synemosyna formica, 
another American spider observed by Peckham, has the usual formula, 
but is said to use its second pair of legs as antenme ! 
I have mentioned that the spiders are probably protected from 
birds and other enemies by their resemblance to ants, but there can be 
no doubt that frequently they also thereby gain another very consider- 
able advantage. The ants with which these spiders “ most do congre- 
gate ” are fairly omnivorous feeders, but shew a decided preference for 
sweet juices often to be found exuding from trees, fruit or flowers. To 
these juices como also flies, small beetles and other insects which form 
the natural prey of the spider, and which do not, under the circum- 
stances, particularly fear the ants. Thus while the flies are sucking 
up sweetness in company with the ants, the spider is no doubt able, 
under cover of his disguise, to approach near enough to make a spring 
upon his unsuspecting victim and fix his sharp falces into its body. 
As regards the ants themselves, they do not seem to take any particular 
notice of the spiders, and do not apparently attack them. One spider, a 
mimic of Ocophylla smaragdina was found by me in a nest of these ants 
with its little silky shelter attached to one of the leaves which formed 
part of the abode of probably the most fierce of all the ants found in 
Bengal. It may also be supposed that the spider does not attack or 
annoy the ants. 
II. A List of the Butterflies of Engano, with some Remarks on the 
Danaidee. — By William Doherty, Cincinnati, U. 8. A. Com- 
municated by the Natural History Secretary. 
[Received 21st February, 1891, read 4th Haroh, 1891.] 
(With Plate I, figs. 1 — 4.) 
The long parallel lines of upheaval which characterize Burma are 
continued far into the Malayan region in the form of three great chains 
of islands and mountains. The most eastern of these, and the oldest, 
being chiefly composed of primitive rocks, consists of the Malay 
Peninsula, itself built up of several parallel ranges, the Riouw and 
I J i n gg a groups, Banka and Billiton. The most western includes the 
Audamans and Nicobars, and the line of islands which may be called 
the Nias group, lying west of Sumatra, extending perhaps to west- 
ern Java. Between these two the large island of Sumatra has been 
formed, probably in times goologically receut. No doubt some parts 
of Sumatra are composed of older rocks, but till the great volcanic up- 
