1938] 
The Genus Lithurgus 
147 
Margin of prothorax only very thinly fasciate; scopa 
yellowish-orange socorroensis new species 
5. Pubescence at tip of abdomen bright ferruginous 
cipicalis Cresson 
Pubescence at tip of abdomen black 6. 
6. Apical margin of clypeus with a single median emargi- 
nation ; scopa without black hairs 
apicalis var. opuntiae Cockerell 2 
Apical margin of clypeus with a small median emargi- 
nation and a slightly deeper one on each side; scopa 
on sixth sternum black, with a few black hairs usually 
on the fifth also bruesi Mitchell 
7. Clypeus and supraclypeal area quite densely rugose or 
punctate 8. 
At least the supraclypeal area shining and very sparsely 
punctate 9. 
8. Labrum with a prominent basal tubercle visible just 
above mandibles gibbosus Smith 
Labrum not tuberculate echinocacti Cockerell 
9. Labrum with a pair of conspicuous parallel spines 
toward the base bruesi Mitchell 
Labrum with a single median tubercle or none 10. 
10. Labrum with a basal median spine-like acute tubercle; 
supraclypeal area almost impunctate, the clypeus 
quite closely punctate socorroensis new species 
Labrum not tuberculate ; supraclypeal area with sparse 
scattered punctures, the clypeus also sparsely punc- 
tate medially 11. 
2 L. arizonensis ? Cockerell has been described recently (Bull. So. 
Calif. Ac. Sc. 36, p. 108, 1938), but I was unaware of it at the time 
this manuscript was prepared. According to its description, it would 
run in this key to opuntiae, and is apparently very closely allied to it. 
Cockerell separates it from opuntiae ? by its more flattened clypeus, 
having larger punctures, and the facial punctures deeper and more 
widely separated. It seems probable that it is another variant of 
apicalis, but I am not warranted in forming any positive opinion until 
I have had the opportunity of examining it, and of examining a longer 
series of var. opuntiae than has hitherto been possible. 
