3i8 TUE CANADIAN ENTOMOLOOI8T. 



Pierce gives a list of 14 Aivlrenidae in which the transverse cubital 

 nervures are sometimes wanting. The h'st is credited to Crawford, but, 

 except for one name, it was copied from my list in Tr. Am. Knt. Soc, 

 XXVm. 1S9. 1902. 



Of the 14 species, 7 are known to be parasitized, a pretty good i>er- 



ceiuage. There is evidently a relation, but not what is sup|X)sed by 



Pierce and Crawford. Proiopis has a nervure wanting, and so do the 



I'anurgidii'. In a general way small bees seem to be more likely to be 



st\l(»pized, and more likely to Ijsc the transverse cubiials. I have 



observed ihei-e nervures wanting in the following 18 species of local 



Andrenida; : Andrtna arabis, nubicu/a, tiothoscordi, ery/hroi^astra, 



geratiii, i/Iinoeitsts, platypatia, Pterandrena asteris, solldaj^inis, krigiana, 



Opatidreiia biputictata, personata, Robertionii, Cresionii, Trac/iandrena 



c/aytonice, /lippotes, P'orbeiii, and almost always in Paraudrtna andren- 



oides. Nine of these are st>lopized species. The species of Andrena 



are small or middle sized. Those of Pterandrtna arc the smallest. 



Trachaiuhena is composed of middle sized species, but daytotiue is the 



smallest. Among bees, at least, the siylopized species are generally small, 



and they are the ones usually losing a transverse cubital. Among some 



large bees, when the second cubital cell is small and the nervures closely 



approximated, there is a tendency for one of the transverse cubitals to 



be obliterated. Amonj^ the Nomadidie, which are not stylopized, I 



have found a transverse cubital wantfng in Centrias americanus, rubi- 



(tifidus, P/ior integer, Gnathias cuneatm, Nomada Cressonii, Sayi, 



iliiiioensis, parvci, and almost always in Heminomada obliterata. In 



Sphecodini I have found transverse cubiials wanting in Sphecodes 



arvensis, Drepauium /a/ci/erum, Sphecodium pitnpine/la, Ciessonii, 



Machceris stygia, and always in Dia/onia antennat iir. The veins are 



wanting in 1 7 out of 49 Andrenidae, 9 out of 23 Nomadida*, 6 out of 



12 Sphecodini. The second transverse cubital is sometimes wanting in 



Chloralictus sparsus, which is a styloj)ized species, and almost always in 



Dialictus anoma/iiSy which is not known to be so. Thus the tendency to 



obliteration is no more evident in the .Andrenidae, which are stylopized, 



than in the Nomadida.' and Sphecodini, which are not. The apparent 



correlation is the result of the occurrence of both phenomena in bees of 



small size. 



In regard to the copulation of stylopized bees, I have observed three 

 cases : Andrena salictaria, both sexes bearing Siylops ; Parandrenn 

 andrenoidei, the !|! stylopized ; Pseudopanurgm rudbeckuty the ^ stylopized. 



