1967] Wilson , Carpenter , Brown — Mesozoic Ants II 
and the aculeate wasps. However, we feel that the metapleural 
gland, the nodiform, posteriorly constricted petiole, and the generally 
ant-like overall habitus place this species among the primitive ants 
rather than the wasps. However, if we are mistaken about the pres- 
ence of the metapleural gland, it would be possible to consider 
Sphecomyrma as a wasp rather than an ant. 
Which of the aculeate wasp groups might have given rise to the 
Sphecomyrminae ? In Table 2 we present a scheme by Dr. Howard 
E. Evans, who has compared the Mesozoic ant with a wide range 
of modern aculeate families (fossil wasps are too scarce to be of much 
use). It can be seen that the Tiphiidae, and in particular the genus 
Methocha , come closest. ( Methocha is impressively similar in de- 
tails of thoracic structure, as shown in Figure 3 ) . But we agree with 
Evans that such a comparison must be treated very carefully. The 
modern aculeate wasps are specialized both morphologically and 
ecologically: for example, Methocha of several species are known to 
TABLE 1 
Relationships of the Principal Character States 
of Sphecomyrma freyi 
Aculeate Other primitive Both aculeate 
wasps only ants only wasps and 
primitive ants 
Narrow bidentate 
mandibles + 
Well-formed 
slender scapes 
Long, filiform 
funiculi ~b 
Large compound 
eyes "b 
Well-formed 
ocelli ~b 
Broad, simple 
clypeus t 
Reduced, apterous 
thorax + 
Mesonotum with 
separate, dis- 
tinctly convex + 
scutum and 
scutellum 
Metapleural gland 
Petiole with node 
+ 
deeply constricted 
front and rear 
+ 
Gaster ovoid, 
unconstricted 
+ 
Extrusible sting 
+ 
