Supplement to Harvesting Ants and Trap-door Spiders

Abstract

MR. MOGGRIDGE'S original work was reviewed in NATURE, vol. vii. p. 337, and we have already a mass of additional matter, paged continuously so as to form one volume when bound up with the first part. Only twenty pages are here devoted to the ants, yet we find several observations of great interest to the philosophic entomologist. Thus, the actions of lizards and tiger-beetles in attacking the ants were closely observed. The lizards only eat the winged males and females, but show great fear of the workers, always keeping out of their way; and the workers protect the winged ants by surrounding and swarming over them, so that the lizards can only occasionally dash at an outlying straggler. The Tiger-Beetle (Cicindela) devours the workers, but only attacks them with great precaution, keeping out of the way of the main body and seizing stragglers by a bite just behind the neck. If it fails to seize them in this exact spot it leaves go again, evidently knowing that if the ant's jaws once close on any part of its legs or antennas they will never leave go, even after death. These observations apply to the two species of South European Harvesting Ants, Atta structor and A. barbara, and they furnish a clue to the use and purport of the large bodies of workers, which act as guards to the males and females. They also explain the use of the spines, hooks, and bristles with which so many of the weaker forms of ants are armed, as well as the occurrence of a proportion of soldiers—large-headed workers whose only function is to attack and drive away certain specially dangerous enemies. Some of these large-headed workers are essentially a huge pair of jaws with just enough body to carry them about, and whose sole object in life is to fasten on some special enemy and sacrifice themselves for the good of the community. The most important problem remaining for solution in connection with these harvesting ants is, how they contrive to keep the seeds in their granaries from germinating. Mr. Moggridge lias proved that formic acid or its vapour has no influence, that the presence of the ants is necessary to prevent ger-mination3 but that their presence alone does not prevent it. Is it not probable that the whole secret consists in the ants continually using for food those seeds which begin to germinate, and that there always remain many seeds whose germination is delayed?

Supplement to Harvesting Ants and Trap-door Spiders.

By J. Traherne Moggridge. With specific descriptions of the Spiders, by the Rev. O. Pickard-Cambridge. (Reeve and Co., 1874.)