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POPULAR SCIENCE REVIEW. 
triumph to the nest. All the fruit-like bodies do not ripen at 
once, but successively, so that the ants are kept about the young- 
leaf for some time after it unfolds. Thus the young leaf is always 
guarded by the ants.” This reciprocity of services between the 
insects and the plant is very remarkable. Mr. Belt gives other 
details on the subject, for which reference must be made to his 
work. He adds that the Acacia is sometimes, although less fre- 
quently, tenanted by another ant, a species of Crematog aster, 
which occupies the whole tree to the exclusion of the Pseu- 
domyrma, and makes its entrances to the thorns near the centre 
of one of each pair, and not near the end. Although the thorns 
are so hollowed out that only the hardened shell remains, the 
tree receives no injury from the ants, and the thorns increase in 
size in consequence of their visits. Mr. Belt says that plants of 
the Acacia raised in his garden were not touched by the ants, 
and that the thorns turned yellow, and dried up into dead but 
persistent prickles ; this, however, may have been due to an un- 
suitability of habitat. Mr. F. Smith, of the British Museum, 
has directed my attention to his description* of a species of 
Pseudomyrma (P. modesta ), forwarded to him by Mr. Stretch, 
from Panama. He gives the following account of the nest of 
this ant : “ It consists of the large hollow thorns or spines of a 
species of Acacia . The spines are three inches long, tapering 
to a point from a broad base. The ants gnaw a small hole to- 
wards the point of the spine ; the broad base then forms an 
admirable domicile for their young brood. There are no cells 
o i divisions of any kind for the reception of eggs or larva. The 
number of pupae found in one nest was seventy-nine, and about 
twenty mature ants, all workers. These ants sting very 
violently.” 
The leaf-dwellings of ants are found chiefly in some closely- 
allied genera of Melastomacece, all natives of South America. 
It is worthy of remark that, with the exception of Myrmecodia 
and Hydnopliytum, which are in almost every respect very 
different from the other ant-inhabited plants, all the genera 
which have come under my notice in connection with this sub- 
ject are South American, and I find no instance of similar 
phenomena either in Europe or Africa. In these Melastoma- 
cece, , belonging to the genera Tococa , Ccdophysa, Maieta, Mi- 
crophysca, and Myrmidone, it is usually the petiole which is 
adapted as a residence for the ants. The description given by 
Aubletf of the means by which this is effected in Tococa 
guianensis will apply, with slight modifications, to the other 
genera. “The leaves,” he says, “are attached to the stems by 
* 11 Trans. Entom. Soc.,” 3rd series, vol i. part 1. 
t “ Plantes de Guiane,” i. 439. 
