122 



their full size and characteristic shape, or at any rate at once 

 cease growing and turn brown as soon as they have been hollowed 

 out, suggests an interesting question as to the true cause of the 

 enlargement of the thorns. 



The important lacuna in Belt's account is the lack of any 

 observations on the first invasion of the young acacia by the 

 ants. That he endeavoured to answer this question, but failed, 

 is clear from the following quotation : "I sowed the seeds of 

 the acacia in my garden, and reared some young plants. Ants 

 of man}' kinds were numerous ; but none of them took to the 

 thorns for shelter, nor the glands and fruit-like bodies for food ; 

 for as I have already mentioned, the species that attend on the 

 thorns are not found in the forest. The leaf-cutting ants attacked 

 the young plants and defoliated them, but I have never seen 

 any of the trees out on the savannahs that are guarded by the 

 Pseudomyrma touched b}' them, and have no doubt the acacia 

 is protected from them by its little warriors." 



It is regrettable that Belt failed to observe seedling acacias 

 in their native savannahs, for had he done so he might have 

 modified his views in regard to the myrmecophily of these plants. 

 But seedling acacias are rare even where the bushes and trees 

 abound. Quirigua was the only locality in which I succeeded 

 in finding them, probably because the dry season was prevailing 

 in all the other places I visited in Guatemala. In the clearings 

 that were being made for the banana plantations, I found many 

 young plants of A. cornígera between 8 in. and 2 ft. in height. 

 Several of these, though vigorous and almost in the very paths 

 of large colonies of leaf-cutters, were nevertheless perfectly 

 free from Pseudomyrmas. The thorns of others, however, con- 

 tained isolated, recently fecundated queens of Ps. fulvescens or 

 Ps. gracilis in the act of establishing their colonies. Brief de- 

 scriptions, drawn from my note-book, of two of these plants will 

 suffice. One, only 8 in. high, bore but a single pair of thorns, 

 which were hollow and contained a soHtary deälated queen of 

 Ps. fulvescens. She had made the typical opening near the tip 

 of one of the thorns, and was evidently waiting for the eggs to 

 mature in her ovaries. Another plant, 14 in. high, was more 

 interesting. It bore 5 pairs of thorns, each of the three basal 

 pairs of which was inhabited by a deälated queen ; the two 



