National Geographic : 1912 Aug
gions, where the summers are so short that the ants have to utilize every bit of mid-day heat in order to bring their young to ma turity. The mound is riddled with chambers and galleries and is not only fully exposed to the sun, so that its tem perature is several degrees higher than that of the sur rounding soil, but its slopes are often constructed in such a manner to catch the heat rays perpendicularly and form the most effective re gions of the heavens. This orientation of the nests is Photo by the Author indeed often so conspicuous LARV2E OF THE TEXAN AGRICULTURAL ANT (Pogono- and definite that they can be myrmex molefaciens) used as compasses (see pic The brilliant white color and tensity of the skin in these tures, pages 742, 759). grub-like creatures is due to the great accumulations of fat, In the tropics where the which will be used, in part at least, during pupation in build- soil is often saturated or ing up the body of the adult ant. Magnification about five flooded with water during diameters. faooded with water during the rainy season, and where ANTS THAT BUILD INCUBATORS devices for conserving the heat are quite unnecessary, many ants have learned to Ants no doubt originally nested in the construct paper nests on the trees. Such earth, and the majority of species still nests superficially resemble the nests of prefer this habitat. It was while living wasps. They contain no combs, how in this plastic material that they learned ever, but only a maze of irregular, inter to prefer irregular galleries and cham- communicating galleries and chambers. bers and to become great opportunists, in A few tropical species belonging to three marked contrast with the social wasps different genera (LEcophylla,Myrma, and and bees, which have never been able to Camponotus) inhabit nests consisting in depart from their habit of rearing their part at least of a fine silken web. young in combs made of a refractory sub stance like paper or of an expensive se- REPAIRING THE NEST WITH SILK cretion like wax. It was long a mystery how ants could The ants early discovered the great ad- manufacture silk, but it has been recently vantages of being able to carry their shown that the ants themselves do not brood from place to place when danger spin the silk, but use their larvae for this threatened. purpose. The process can be actually In connection with this free method of observed by making a rent in the wall of dealing with the brood, they were also the nest and then following the move led to add to the original subterranean ments of the ants under a magnifying nest a kind of tepidarium or incubator, glass. They separate into two brigades, in which the young could be placed dur- one of which stations itself on the outside ing the warmest hours of the day for the of the nest and draws the edges of the purpose of hastening their development rent as close together as possible by pull (see pictures, page 759). This incu- ing with claws and mandibles, while the bator is the mound or dome of pebbles or other, inside the nest, moves the spinning vegetable detritus, which surmounts the larvae back and forth across the gap till subterranean nest of many of the more it is filled out with a dense felt-work of conspicuous species of North America extremely fine silken threads (see picture, and Eurasia, especially in mountain re- page 764).