THE EXTERNAL STRUCTURE OF AXTS. 



3 3 



notum may still be recognized as very small sclerites, but in the workers 

 of the highest and most specialized ants of the genera Formica and 

 Cainponotns the thorax appears to consist of three similar segments. 



FIG. 8. Thorax of female, ergatoid and worker Ponerine ants in profile. (Emery.) 

 A, Myrmecia pyriformis, dealated female ; B, M. spadicca, ergatoid female : C, M. 

 pyriformis, worker ; msn, mesonotum ; the remaining letters the same as in Figs. 6 and 7. 



owing to the disappearance of the scutellum, paraptera and metanotum 

 as separate sclerites and to the fusion of the various elements in the 

 pleural region of each segment. 



The legs of the ant show much less variation in structure than the 



a 



FIG. g. Median sagittal sections to show difference of development of thoracic 

 segments in the worker and female Myrmica rubra. (Janet.) A, Worker; B, female; 

 .-/, posterior portion of head; b, prothorax ; c, mesothorax ; </, metathorax ; e, epino- 

 tum (first abdominal segment) ; f, petiole (second abdominal segment). 



