42 HYMENOPTEKA. 



DIELOCEEA. 



Hybtoma, § 2, King, Jahrb. d. Insect, i. p. 240 (1834). 



Diebcerus, Curtis, Trans. Linn. Soc. xix. p. 249 (1845). 



Ptilia, Section 2, Norton, Trans. Amer. Ent. Soc. ii. p, 367 (1869) . 



Ptenos, Norton, 1. c. iv. p. 77 (1872). 



Hemidianeura, Kirby, List of Hymen, i. p. 48 (1882) . 



In this genus and in 'Ptilia the first transverse cubital nervure may be absent 

 entirely, or be but very faintly indicated even in species where it is normally present ; 

 in other cases its absence would appear to be a secondary sexual character. The main 

 distinction between Dielocera and Ptilia is that in the former the second cubital 

 cellule (or first when the first transverse cubital nervure is absent) receives both recur- 

 rent nervures, while in Ptilia is receives only one. 



I cannot look upon the absence of the first transverse cubital nervure as of generic 

 value, because, as above stated, it tends to become obsolete even in species where it, 

 as a rule, is found ; in nearly all the Hylotomina it is bullated, and there can be no 

 doubt that the " bulla " is the cause of the partial or complete obliteration of the 

 nervure. Even the point of difference between Dielocera and Ptilia I have just 

 mentioned must be accepted with reserve; for I find that when the second recur- 

 rent nervure is interstitial (L e. is united to the transverse cubital), it is apt to vary 

 in position and may be received either in the second or third cubital cellule. I have 

 not yet succeeded in finding other structural characters whereby these forms may be 

 generically separated. 



1. Dielocera biramosa. (Tab, I. figg, 10, 2 , Didymia Mramosa ; 10 a, labrum ; 

 10 #, maxilla; 10 c, mandible.) 



Hybtoma biramosa, Klug, Jahrb. d. Insect, i. p. 242. 64 (1834) \ 

 Ptilia biramosa, Norton, Trans. Amer. Ent. Soc. i. p. 61 (1867) . 

 Ptenus (?) biramosus, Kirby, List of Hymen, i. p. 532. 



Eab. Mexico \ Vera Cruz, Orizaba, 



2. Dielocera imitatrix. (Tab. I. figg. 4, $ , Ptilia imitatrix; 4 a, head.) 



Nigra, pronoto, tegulis, mesosterno scutelloque rufo-testaceis ; pedibus albis, tarsi tibiisque posticis dimidio 



apicali nigris ; alis fumatis. 

 Long. 11 millim. 



Eab. Guatemala, Duenas (Champion). 



The antennae are a little longer than the thorax, shortly and closely pilose. The 

 clypeus bears a few scattered punctures, and is slightly incised at the apex. The 

 sutures on the vertex are deep and broad ; there is a transverse one behind the ocelli ; 

 the frontal area is long, depressed ; the labrum is piceous ; the outer sides of the 

 mesonotum are dull testaceous. Only the upper fourth of the mesosternum is reddish 



