286 WILLIAM J. FOX. 



MALES. 



Second submarginal cell triangular, smaller than tliird, the first and second 

 transverso-cubital veins uniting above; head, thorax and abdomen 

 coarsely punctured : first ventral abdominal segment with a hook at 

 base, the second ventral unarmed ; hind coxse with a blunt tooth or 

 lamellate process above unicolor Say. 



Second submarginal cell elongate, larger than third, the first and second trans- 

 verso-cubital veins widely separated above; body finely punctured; 

 first ventral not hooked 2. 



2. Hind coxse above with a distinct spine; insect black, at most with tip of abdo- 

 men reddish ; third submarginal narrowed above, higher than long. 



parvula Fox. 



Hind coxse witli a blunt tooth or lamellate process; head, thoi'ax and legs 



black, abdomen ferruginous; third submarginal quadrate, longer than 



high ruflveiitris Blake. 



FEMALES. 



M. thoracica, the only American species known in the female sex, 

 is coarsely punctured ; ferruginous, with abdomen more or less 

 blackish above ; first segment transversely carinated above, beneath 

 prominently produced at base; the front of head is usually blackish. 



1. Myrmosa unicolor Say. 



Myrmosa unicolor Say, Keating's Narrative Long's Expedition St. Peter's 



River, etc., ii, 331, % , 1824; LeConte's Ed. Say's Entom., i, 222, 1859. 

 Ischioceras riigosa Provancher, Nat. Can., xiii, 8, % (not 9 )> 1882. 

 Mutilla unicolor Dal la Torre, Cat. Hym., viii, 94. 1897. 



Canada, southward to Virginia, thence westward to Colorado. 

 Very variable in size. The base of second ventral segment may be 

 tuberculate or not. I have Provancher's type of Ischioceras riigosa 

 before me. It is identical with M. unicolor, save for an anomaly 

 of venation, the second transverso-cubital vein being abbreviated 

 and represented by a mere stump, which does not reach half-way 

 to the marginal cell. The description by Provancher of the male 

 probably applies to Methoca stygia. 



2. Myrmosa parvula Fox. 



Myrmom pitrvula Fox, Journ. N. Y. Ent. Soc, 53, % , 1893. 

 Mntilla antisemitica Dalla Torre, Cat. Hym., viii, 10, 1897. 



Illinois ; Montana. 



3. Myrmosa riifiveiitris Blake. 



Myrmosa rufiventris Blake, Tr. Am. Ent. Soc, vii. 254. %, 1879. 

 Mutilla erythrogaster Dalla Torre, Cat. Hym., viii, 36, 1897. 



Nevada. Only the unique type seen. 



