-S .1\'TS. 



Landois and Sharp, /'. c., at the base of the first gastric segment, and 

 also on the corresponding part. of the postpetiole. These two segments 

 certainly admit of the greatest amplitude and freedom of movement 

 and are, therefore, the most favorable spots for the development of 

 organs like those under discussion. In J\lynnica ruhra there are more 

 than 50 ridges to the postpetiolar file, but in the organ at the base of the 

 paster there are more than 130 and these are much finer. The ridges, 

 however, are twice as broad in the anterior as they are in the 

 posterior portion of the gastric file. It appears, therefore, that the 

 most highly developed stridulatory surfaces of the Myrmicinse and 

 Ponerinae are not strictly homologous, since in the former subfamily 

 the principal organ is situated on the third abdominal, whereas the only 

 stridulatory file of the latter is on the second abdominal segment. In 

 both cases, however, the main organ is at the base of the first gastric 

 segment. What seem to be incipient stages in the development of the 

 organ from ordinary polygonal asperities of the chitinous integument, 

 are seen in the Dorylinae. Of the first gastric segment in one genus of 

 this subfamily Sharp says : " I have examined workers of several species 

 of Eciton, and find that they have no stridulatory organ, the sculpture 

 being uniform all over the dorsum of the neck of the segment." My 

 own observations on the workers of several species of Eciton, Quietus, 

 Dorylus and Chelioinynnc.v confirm this statement. In all these genera 

 the neck of the postpetiole and that of the first gastric segment are 

 covered with polygonal asperities, but these are much more conspicuous 

 than on other portions of the segments, and in one species ( Eciton- 

 opacithorax ) they are transversely lengthened in the mid-dorsal region 

 so that they foreshadow the file ridges of the Ponerinse and Myrmicinse. 



Although the number of segments in the gaster is morphologically 

 eight, when the pedicel consists of a single segment, and seven when it 

 consists of two, only four segments are externally visible in the worker 

 and female and five in the male. The remaining segments are very 

 small and telescoped into the larger ones in front of them: Trachea! 

 stigmata are present on the eight basal abdominal segments, /. c., on 

 the epinotum, pedicel and the five or six basal gastric segments. 



The terminal segments in the female and worker may bear a sting, 

 which is of considerable interest, because it can be traced back to its 

 primitive homologue, the ovipositor. In many Orthoptera, like the 

 katydids and crickets, this organ consists of three pairs of appendages, 

 which, as I have shown (1893), are the modified embryonic legs of the 

 eighth, ninth and tenth abdominal segments. Owing to a very early 

 embryonic fusion of their corresponding segments the pair belonging to 

 the tenth segment moves up and comes to lie between the ninth pair, so 



