134 
Psyche 
[June 
Preserved specimens have been deposited in the collection of the 
U. S. National Museum. 
Discussion 
Spilo?nena and Microstigmus share the following features: setae 
absent from both body and head ; antennal papillae present ; labrum 
semicircular, without an apical emargination or pigmented bands; 
mandibles with three strong apical teeth in the same plane; and 
galeae absent (said to be present but minute in S. vagans). Ammo- 
planus larvae also have antennal papillae, tridentate mandibles and 
no galeae, but the head has many setae and the labrum is slightly 
emarginate. These smilarities suggest that Microstigmus is closely re- 
lated to Spilomena and somewhat more distantly related to Ammo- 
planus. These three genera are quite distinct from the Pemphredonini 
( Pemphredon , Passaloecus, Xylocelia and Stig?nus larvae have been 
described), which possess galeae, lack antennal papillae, have four 
strong mandibular teeth, and have the labrum broad and apically 
emarginate. However, the possibility exists that these lines of dis- 
tinction may be blurred as the larvae of additional pemphredonines 
become known. 
In addition to the above, the larva of Microstigmus evidences sev- 
eral unique features which are no doubt associated with the unusual 
biology of this genus. These include the conical supranal process, 
possibly an adaptation for obtaining purchase in the walls of the cell, 
and the apparent complete absence of spinnerets, which correlates 
with the loss of the cocoon in this genus. The spinulose lobe on the 
inner margin of the mandible is also unique and may be a modification 
for feeding upon Collembola. 
Literature Cited 
Evans, H. E. 
1958. Studies on the larvae of digger wasps. Part IV: Astatinae, 
Larrinae and Pemphredoninae. Trans. Amer. Ent. Soc., 84: 
109-139. 
1959. Studies on the larvae of digger wasps. Part V. Conclusion. 
Trans. Amer. Ent. Soc., 85: 137-191. 
1964. Further studies on the larvae of digger wasps (Hymenoptera, 
Sphecidae). Trans. Amer. Ent. Soc., 90: 235-299. 
Matthews, R. W. 
1967. Nesting biology of the social wasp Microstigmus comes (Hymen- 
optera, Sphecidae, Pemphredoninae). Psyche, in press. 
Myers, J. G. 
1934. Two Collembola-collecting crabronids in Trinidad. Trans. Roy. 
Ent. Soc. London, 82: 23-26. 
