1965] 
Taylor — Genus Simpone 
289 
1. Smaller size (about as in chapmani) , with much narrower 
head and proportionately much larger eyes, which are less widely 
separated relative to their maximum diameter; postpetiole distinctly 
longer than broad in dorsal view (length 1.12 X width). 
2. Anterior clypeal border strongly biconcave in frontal view, 
with a distinct median anterior tooth. 
3. Transverse occipital and anterior petiolar carinae as in chap- 
mani. 
4. Lateral mesosomal suturation weaker, as in chapmani. Dorsal 
promesonotal suture distinctly transversely ribbed ; mesometanotal 
suture lacking on mesosomal dorsum. 
5. Sides of postpetiole as in chapmani , almost parallel in dorsal 
view. 
6. Sculpturation generally as in chapmani , but scaly microsculp- 
ture lacking on sides of pronotum, which are smooth and shining. 
7. Vestiture much more abundant than in either gressitti or 
chapmani. Moderately long reclinate to sub-erect hairs fairly abun- 
dant on head, those at center of frons shortest and least abundant, 
those along frontal carinae more erect, a single more elongate hair 
above each eye. Dorsa of mesosoma, petiole and postpetiole with 
similar, but somewhat longer pilosity, least abundant on disc of prono- 
tum, best developed on propodeum and petiole. Single longer hairs 
on pronotal humeri, on petiole slightly behind its anterior corners, 
and dorso-laterally at about mid-length of postpetiole. Anterior 
gastric pilosity slightly less abundant and shorter than that of nodes, 
several more elongate hairs laterally, apex surrounded by long arched 
hairs. The subpetiolar process is partly obscured by glue; it appears 
that about 10-12 long hairs normally break its ventral profile; they 
do not form a regular brush-like series as in gressitti. 
Relationships. S. bakeri is more similar, and probably more closely 
related to chapmani than to gressitti. It is easily distinguished from 
chapmani by the cephalic and ocular proportions, the structure of the 
anterior clypeal border, and the more abundant vestiture. These 
three species form an apparently morphoclinal sequence (bakeri — > 
chap??iani—> gressitti) in various characters, including decrease in 
relative size of the eyes (i.e. OI), and increase in relative head width 
(i.e. Cl), in the spacing of the eyes relative to their maximum diam- 
eter, and in the width of the postpetiolar dorsum relative to its length. 
Reduction and specialization of the pilosity also follow this sequence. 
S. bakeri appears to have the most primitive habitus and probably 
most resembles the ancestral Indo-Australian stock, except perhaps 
for its possession of a median clypeal tooth, and the lack of a dorsal 
mesometanotal suture. 
