Insects. 2039 



to infest Bombi and Odyneri more than any other hymenopterous in- 

 sects ; the former are indeed sometimes unable to fly, so numerous are 

 these parasites found upon them ; and the metathorax and femora of 

 Odyneri are frequently completely covered by them. 



I am not acquainted with any other parasite which infests these 

 bees, but large numbers of them fall a prey to certain species of fos- 

 sorial Hymenoptera belonging to the genus Cerceris. I have captured 

 one species, C. ornata, conveying to her burrow specimens of Halic- 

 tus rubicundus, fulvocinctus and obovatus : Cerceris ornata is very 

 abundant in some districts, and must destroy immense numbers of 

 Halicti. 



It is the generally-received opinion that the species of Sphecodes 

 are parasitic upon the Halicti. St. Fargeau and Walckenaer are both 

 of this opinion, but I am not aware that the fact has ever been proved. 

 I have once or twice observed a species of Sphecodes in the act of 

 burrowing, and this fact leads me to doubt their parasitism. It may 

 be possible that they were endeavouring to reopen the closed burrows 

 of Halicti, but I do not know that such habit has been observed in 

 any of the parasitic bees. 



Genus. — Halictus, Latreille, Walckenaer, St. Fargeau, Curtis. 

 Andrena, Fab., Panz., Spinola, Oliv. Hylceus, Fab., Panz. Prosopis, 

 Fab. Apis, Panz., Rossi, Fourcroy, Schrank. Lasioglossum, Curt. 

 Melitta, Kirby. 



Generic characters. — Head usually a little narrower than the tho- 

 rax, sub-triangular ; the stemmata placed in a curve on the vertex ; 

 the antennae inserted in the middle of the face, geniculated, twelve- 

 jointed in the females, the basal joint elongate; the tongue short, 

 acute, and pubescent at the apex ; the middle tooth emarginate ; the 

 labial palpi four-jointed, the basal joint longest, arcuate, the rest of 

 equal length ; the maxillary palpi six -jointed, the three basal joints 

 shortest ; the mandibles bidentate or notched at their apex, pubescent 

 externally ; the clypeus convex. Thorax usually ovate ; wings with 

 one marginal and three complete submarginal cells, the first about as 

 long as the two following, the second nearly quadrate, receiving the 

 first recurrent nervure beyond the middle, the third narrower towards 

 the marginal, receiving the second recurrent nervure beyond the mid- 

 dle. Abdomen oblong-ovate, pubescent, and having at the apex a 



