THE VOYAGE OF THE BEAGLE 45 



la Plata. Do the very numerous spiders and rapacious 

 Hymenoptera supply the place of the carnivorous beetles? 

 The carrion-feeders and Brachelytra are very uncommon ; 

 on the other hand, the Rhyncophora and Chrysomelidae, all 

 of which depend on the vegetable world for subsistence,' are 

 present in astonishing numbers. I do not here refer to the 

 number of different species, but to that of the individual 

 insects ; for on this it is that the most striking character in 

 the entomology of different countries depends. The orders 

 Orthoptera and Hemiptera are particularly numerous; as 

 likewise is the stinging division of the Hymenoptera; the 

 bees, perhaps, being excepted. A person, on first entering a 

 tropical forest, is astonished at the labours of the ants: well- 

 beaten paths branch off in every direction, on which an army 

 of never-failing foragers may be seen, some going forth, and 

 others returning, burdened with pieces of green leaf, often 

 larger than their own bodies. 



A small dark-coloured ant sometimes migrates in count- 

 less numbers. One day, at Bahia, my attention was drawn 

 by observing many spiders, cockroaches, and other insects, 

 and some lizards, rushing in the greatest agitation across 

 a bare piece of ground. A little way behind, every stalk and 

 leaf was blackened by a small ant. The swarm having 

 crossed the bare space, divided itself, and descended an old 

 wall. By this means many insects were fairly enclosed; and 

 the efforts which the poor little creatures made to extricate 

 themselves from such a death were wonderful. When the 

 ants came to the road they changed their course, and in 

 narrow files reascended the wall. Having placed a small 

 stone so as to intercept one of the lines, the whole body 

 attacked it, and then immediately retired. Shortly afterwards 

 another body came to the charge, and again having failed 

 to make any impression, this line of march was entirely 

 given up. By going an inch round, the file might have 

 avoided the stone, and this doubtless would have happened, 

 if it had been originally there: but having been attacked, the 

 lion-hearted little warriors scorned the idea of yielding. 



Certain wasp-like insects, which construct in the corners 

 of the verandahs clay cells for their larvae, are very numer- 

 ous in the neighbourhood of Rio. These cells they stuff full 



