Polyrhachis (Myrma) laboriosa F. Smith

Wheeler, W. M., 1922, The ants collected by the American Museum Congo Expedition., Bulletin of the American Museum of Natural History 45, pp. 39-269 : 258-259

Polyrhachis (Myrma) laboriosa F. Smith

Plate XXII, Figure 2; Text Figure 69 Six workers from Stanleyville and Bafwasende, without further data and a number of workers, larvae, and cocoons from a nest at Niangara (Lang and Chapin).

This species is easily distinguished from all the other African members of the genus by the peculiar petiole, which bears a single pair of long, hook-shaped spines. The nest (Pl. XXII, fig. 2) seen by Mr. Lang is described as follows. " It was found on a small tree about three meters from the ground and was 16 centimeters wide, built in a fork between a cluster of finer twigs and consisted of old vegetable fibres and leaves fastened together. It was naturally extremely light, as no soil had been used in its construction. The general color outside was dark gray. Its walls were very thin, scarcely one millimeter in thickness. As far as I could see, there were many entrances, though they were somewhat damaged. Still, a great many intact openings were visible. The fine hairs on the abdomen of this ant are conspicuously bronzy. When disturbed, the workers make a rattling noise by striking the nest with their abdomens. They bend the abdomen forward between their legs and discharge from its tip a copious spray of formic acid, which is quickly diffused through the air."

A nest of this ant, described and figured many years ago by Mayi" and Aurivillius,1 was 17 cm. long, 7.7 cm. broad, and 5 cm. thick. It was rather triangular in outline, with a large opening at one end and several small openings scattered over the surface. It was attached to some thin, leafy twigs and consisted of brown, fibrous vegetable detritus resembling decomposing cowdung, agglutinated "by means of a glue-like substance." The interior contained partitions of a similar structure.

Examination of the nest fragments contained in the vial with the workers from Niangara shows that the coarse vegetable particles are bound together by a small quantity of silk. This was also noticed by Santschi in two nests which he examined.1 Concerning one of them, containing only the mother queen and her first brood of larvae and still in process of construction, he remarks: "The walls of the nest already contain silk, which seems to show that the female is able to use the larvae as shuttles, or perhaps the young larvae spin the silk spontaneously around themselves on vegetable detritus placed at their disposal." That the latter supposition is probably erroneous is evident from what is known concerning the behavior of the female Oecophylla when founding her nest.