108 
Psyche 
[June 
When the narrow-leaved Triplaris is inhabited by 
Pseudomyrma triplarina, it ranks with the terrible nettle 
( Jatropha wrens L.) that grows in much the same sort of 
place. Both plants offer tempting holds on the steep slopes 
along the brooks, and a few stings from either the nettle 
or the ants will cause the hands to swell painfully. Ants 
and their brood occupy cavities in the central stem and its 
lateral branches throughout the Triplaris, except near the 
base of the larger trees. The cavities, which are continu- 
ous and are apparently cut through the nodes by the ants, 
may be occupied up to the last or next to the last internode 
below the terminal bud. The entrances are perpendicular 
slits in the stem or branches and are about 120° around 
the stem from the base of the leaf next above. They are 
usually just below a node, but may be more than half way 
down to the node below. There is almost always at least 
one entrance to a node, and there may be several, one above 
the other. 
In very young stems the medullary cavity is about half 
the diameter of the stem, nearly round in cross-section, 
except for the depressions noted below, and somewhat en- 
larged between the nodes. The passage through each node 
is greatly constricted. In stems an inch and a half in di- 
ameter the entrance may remain open, but the cavity even 
in the oldest stems is scarcely or not at all larger than in 
young twigs. The walls of the cavities in the latter are 
brown; in old twigs, black. 
The depressions mentioned above are vertical, slit-like 
grooves in the walls of the cavities and are of two kinds, 
those which open into entrances and those which extend 
only to the inner surface of the bark and are used to house 
Coccids. The position of the entrances has been described ; 
the Coccid houses have a rather more irregular location, 
but often seem to be incompleted entrances, to which in 
many cases they correspond in position. They are fre- 
quently placed just below leaf attachments, however, where 
there is often a smooth, slightly depressed area on the ex- 
ternal surface of the bark. Whether these “Coccid houses” 
are natural or cut by the ants was not ascertained. 
The Colombian Triplaris and its ants had been previ- 
ously observed by Forel, and Dr. Salt. We quote the latter’s 
