No. 1774. 



THORAX OF HYMENOPTERA—SNODORASS. 



81 



The application of anatomical terms to the back plates of the ant 

 thorax b}'' Nassanoff (1889) is such as to indicate that this author's 

 ideas of the thoracic morphology or nomenclature are quite different 

 from those of the present writer. Wlien the same words are used in 

 different senses by two writers an argument on the subject is likely 

 to be very meaningless. The present writer agrees with Janet (1898) 

 in his nomenclature and morphology of most of the thoracic sclerites, 

 except with respect to the limits of the sternum. It is only by dis- 

 associating the parts of the thorax, as Janet did, that their true 

 relations become apparent. 



Finally, the work of Emery (1900) on the thorax of ants must be 



given a special discussion because Emery's views have been adopted 



by Wheeler (1910) in 



Tg 

 \ 



WR 



scl, 



i 



his recent comprehen- 

 sive work on ants. 

 Emery bases his ideas 

 of the formicoid tho- 

 rax on a study of the 

 female Strehlognathus 

 sethiojyicus. The pres- 

 ent writer has not had 

 access to a specimen 

 of this species but 

 the principal thoracic 

 characters are similar 

 in most of the Po- 

 nerine genera. Text 

 figure 18 shows the left 

 side of the thorax of 

 Leptogonys (Lohopelta) 

 elongata. The protho- 

 rax (iVj, Eps^ and the 

 dorsal plates of the 

 other segments {Psc^, 

 Sct^, Scl^, iVg, IT) do not differ from those of other Hymenoptera. In 

 the mesopleurum, however, the limits of the epimerum (Epm^) are 

 almost obliterated, yet a comparison with Pepsis (61, Epm^) leaves 

 no doubt that the indistinctly marked subdivision (fig. 18, Epm^) 

 along the upper part of the posterior margin of the pleurum is the true 

 mesepimerum. A small but distinct internal ridge attests that the 

 faint line {PS2) is the true pleural suture, though it fades out before it 

 reaches either the wing process ( WP2) or the coxal process. The 

 episternal area is divided by an oblique furrow (r) into an alar and a 

 coxal region (Eps^ and eps^) while, again, the dorsal part of the latter 

 is partially cut off by a longitudinal furrow (z). Now, Emery names 

 Proc.N.M. vol.39— 10 6 



Fig. 18. — Lateral view of ant thorax (Leptogonys elongata): 

 Cxi, Cxi, Cxz, cox.E; Epnii, mesepimerum; Eps\, proepisternum; 

 Epsi, eps2, upper and lower subdivisions of mesepisternum; 

 h, scuto-prescutal(parapsidal) suture; //, second abdominal 

 segment; ISp, first abdominal spiracle; IT, propodeum (first 

 abdominal tergum); k, scuto-scutellar suture of mesono- 

 tum; iVi.PRONOTUM; N3, metanotum; Pis, ph, upper and lower 



subdivisions OF the METAPLEURUM: PiYs.METAPOSTNOTUM fused 



WITH IT: PSi, mesopleural suture; Psc2, mesoprescutum; r, 



LATERAL SUTLTRE OF MESEPISTERNUM; S2, MESOSTERNUM; Sch, 

 PRINCIPAL PART OF MESOSCUTELLUM; Sch, ANTERIOR SUBDIVISION 

 OF MESOSCUTELLUM; Sch, MESOSCUTUM; Tg, TEGULA; M''Pi, WPz, 

 PLEURAL "ttlNG PROCESSES; Z, DORSAL SUTURE OF MESEPISTERNUM. 



