[A32]

Ch. 8

March 7/58/ Driver Ant from Africa, given me by F. Smith

Largest workers about thrice as long as smaller this difference can be recognised only by thinking of men 5' 4 inches high working with men 16 ft high. Longest 4/10 of inch long. Breadth of head as 55 to 14, or four times as broad (ie. 3.92) The sizes seem to some extent to run into groups ie some very small, or some very large, but being so graduated that you cd not make defined line between.

On one very big jaw there was decided minute 2d tooth (a) & clear traces of serrations - on other lost specimen merest trace of serrations or pectinations. Jaws as 9:41 ie between 4 & 5 times as long measured in straight line

The largest stag-horned one though appearing cylindrical has on one side a sort of ledge very nearly whole length & this is developed into the 2d tooth and pectinations. In smallest jaws lowest tooth decidedly smallest of 3 teeth.

 

[32v]

N.B mandible one of most striking differences between the 2 classes of workers in other species — get drawing of Eciton.

 

[33]

Smallest mandible convex edge nearly straight; while broad nearly flat, hollowed out on one side; with 3 large teeth of which lowest smallest & pectinations between middle & lowest, but in variable degrees. Largest, between 4 & 5 times as long; convex edge much bowed; narrow, subcylindrical, with single very large tooth low down on inner edge. These 2 jaws as different as can well be conceived.

Intermediate grades larger & larger in size. (1) The 3 main teeth equal, pectinations very distinct. (2) The second tooth smaller, the 3d larger, pectinations blunter, whole jaw more bowed & narrower (3) the second tooth much smaller, the third much larger, pectinations reduced to Knobs, more bowed & more cylindrical. These latter characters keep on changing till we reach largest jaw: with no trace of 2d tooth,

[33v]

with no pectinations, & third tooth extremely large & prominent. All these teeth are developments of sort of ledge on one side, which can be seen here in largest tooth - The largest mandible may be compared to Horns of Red deer with single side antler, & the smallest to fallow-deer, palmate, but straight, with 3 main side antlers, & intermediate smaller antlers.