26 o 
Psyche 
[September 
Sphecomyrma, from New Jersey amber, is described as “medium- 
sized”, while Cretavus is a large wasp, with a wing length of io 
mm (thus with a wing-span of about 23 mm and a probable body 
length of 13-18 mm). There may have been a fairly diverse fauna 
of Aculeata of various sizes in the Cretaceous, but it happens that 
the deposits considered here are chiefly favorable for preserving small 
species, which often happen to have reductions in wing venation and 
other specializations. 
The diversity of Aculeata in the Cretaceous (three superfamilies 
certainly and two others probably, as pointed out in the introduction) 
suggests an origin of this group in the Jurassic. Dr. Crowson tells 
me that the rocks in which Archisphex was found contain a number 
of insects belonging to Jurassic proups. The Sphecidae undoubtedly 
diversified rapidly in the Cretaceous, as evidenced by Lisponema 
and by quite modern-looking Nyssoninae in the Eocene. Lisponema 
was surely not a ground-nester, and Baltic Amber is rich in Sphecidae 
which probably nested in hollow twigs and other cavities above 
ground (including Passaloecus and other genera related to Lispo- 
nema). If the Sphecidae arose from a scolioid ancestor one would 
have expected them to have been originally associated with the soil. 
In fact they may have been so; twig-nesters tend to occur more 
abundantly in forested areas and may thus become preserved in 
amber much more readily. The Pompilidae are sometimes regarded 
as a somewhat more “primitive” group on the sphecoid stem, but it 
is noteworthy that none are known from prior to the Oligocene 
(Baltic Amber) and that the fossils from that epoch belong mainly 
to archaic genera such as Epipompilus. 
The radiation of the Sphecidae in the Cretaceous makes it seem 
very likely that the bees had their origin in this period and that they 
were therefore on hand to participate in the early diversification of 
the flowering plants. The presence of Procleptes in the Upper 
Cretaceous also suggests that a prototype for the cuckoo wasps was 
available to take advantage of the proliferation of the bees and 
wasps during the Tertiary. 
References 
Carpenter, F. M., et al. 
1934. Insects and Arachnids from Canadian Amber. Univ. Toronto 
Studies, Geo-1. Series, no. 40, pp. 7-62. 
Cockerell, T. D. A. 
1922. An ancient wasp. Nature, 110: 313. 
Evans, H. E. 
1966. The Comparative Ethology and Evolution of the Sand Wasps. 
Harvard Univ. Press, Cambridge, Mass., 526 pp. 
