In the above-mentioned instances the cell which serves as cradle and tomb combined is made by the provident mother. Some wasps, however, have learnt to save time and trouble by walling the victim up in a cell of its own manufacture, or, at least, of its own choosing. This happens to a certain spider in South America, which sits in a little hole in the ground waiting for insects either to pass or come in. The wasp, which is blue like the other, but smaller than our common one, goes about from hole to hole, and when it finds one occupied by a spider, goes a little way into it, and then rushes out, hotly pursued by the owner. When on the point of being overtaken it suddenly turns, grapples with the spider, stings it, drags it back, paralysed, into its own hole, lays an egg by it, and departs, having previously blocked up the entrance with earth. The entrance of the wasp into the spider’s hole, with its retreat, some time afterwards, in feigned alarm, so as to draw the spider out, is certainly an act of great intelligence. The intelligence, however, is surpassed, or exhibited in a more entertaining manner, in the case of another wasp which has been seen to creep noiselessly round to the entrance of a spider’s nest, and then wriggle one of its antennæ in front of the opening. Upon this, the owner of the nest, a very large spider, came out, and was at once stung to death by the wasp. The latter then wriggled an antennæ again, and upon no notice being taken, entered the nest and killed all the young spiders, which he then carried off at his leisure. Other wasps lay their eggs in the nests of humble bees, and the young growing up there prey upon the honey and comb. Amongst ants, again, some of the smaller species are parasitic upon the larger ones, an enforced association which may be very much to the disadvantage of the latter. Especially is this the case where an ant whose Latin name is _Solenopsis fugax_—if it has an English one I do not know it—is the unbidden guest. Lord Avebury tells us that it “makes its chambers and galleries in the walls of the nests of larger species, and is the bitter enemy of its hosts. The latter cannot get at them because they are too large to enter the galleries. The little _solenopses_, therefore, are quite safe, and, as it appears, make incursions into the nurseries of the larger ant, and carry off the larvæ as food. It is as if we had small dwarfs, about eighteen inches to two feet long, harbouring in the walls of our houses, and every now and then carrying off some of our children into their horrid dens.” The insect world is particularly rich in these parasitic relations, but space will not allow me to enlarge upon them further.