i6 



AMS. 



hairs on the lower surface of tlie head greatly elongated and directed 

 forward (Pogonomyrmex, Ocymyrmex, Cratomyrmex, Messor, Goni- 

 oinina, Oxyopomyrmex, Holcomyrtnc.v), or arranged in a tuft on the 

 lower lip ( M ynnccocystits, Melophorus). These hairs, which I have 

 called gular and mental ammoch?et;e ( 1907), are employed by the ants 

 in removing the dust and sand from the strigils or combs on the fore- 

 legs ( I'idc infra, p. 24). In 

 deserts these insects easily 

 become covered with the 

 dry soil or sand and have 

 to remove it from their 

 bodies and limbs by means 

 ar, of the strigils. These or- 



gans are then thrust along 

 the ammochaetse in much 

 the same way as we clean 

 a comb by means of 

 threads. The clypeus and 

 mandibles of many ants are 

 also fringed with unusually 

 long hairs (clypeal and 

 mandibular ammochaetse ) 

 which are employed in re- 

 moving the dust, etc., from the surfaces of the fore-legs. 



The colors of ants are, as a rule, testaceous, yellow, brown, red, or 

 black, but a few genera (Rhytidoponera, Calomyrmex, Macromischa, 

 Iridomyrmex} and a few North American species of Phcidole (metal- 

 Icsccns and splcndidttla) have metallic colors. The non-metallic tints 

 are often highly variable, even within the limits of single species. 

 Color patterns are rarely developed and are usually found only on the 

 upper surface of the gaster, a region which often differs in color from 

 the head and thorax. The appendages, as in other insects, are apt to 

 be paler than the trunk. The coloration of the hairs and pubescence, 

 like that of the surface, may be extremely variable in the same species. 

 To the integument belong also a number of glands, but these will be 

 described in connection with the glands of the internal organs. 



The Head. After this very general review of the segmentation and 

 integument we may take up the different parts of the body in somewhat 

 greater detail. The head varies enormously in shape. It may be cir- 

 cular, elliptical, rectangular or triangular, and all its parts may show an 

 extraordinary diversity of adaptive characters (Fig. 3). It consists 

 of the cranium proper, which is very much constricted behind at its 



FIG. 2. Ammocha?t?e of desert ants. (Ori- 

 ginal.) A, Head of Messor pcrgandei in profile; 

 B, ventral aspect of same ; C, head of Myrmeco- 

 cystns bicolor in profile ; D. ventral aspect of 

 same ; a. clypeal ; b, mandibular ; c. gular ; d, 

 mental ammochsetae. 



