The _Cilissa tricincta_ is perhaps most like the larger species of the genus _Colletes_, both in markings and in the form of the body, but in resemblance of form the second species participates. Although robust insects, and as large as the larger _Andrenæ_, they are yet unprovided with the same ample means for conveying pollen, being destitute of the lock of hair upon the posterior trochanters and the sides of the metathorax are less densely pubescent. The ground colour is brown. Their economy is assumed to resemble that of _Andrena_, although it has not been so closely investigated; for my own part I have never had the opportunity of tracing it to its nidus, having always captured the species upon flowers. They are fond of the trefoil (_Trifolium repens_), and the _C. chrysura_ frequents the _Campanula rotundifolia_, as well as the flowers of the throatwort (_Trachelium_). In their excursions they are usually accompanied by their males. Both species are found in the south and west of England. Section 2. _With entire paraglossæ._ Subsection _c_. LINGUÆ ACUTÆ (acute tongues). a. _With three submarginal cells to the wings._ Genus 6. HALICTUS, _Latreille_. (Plate IV.) MELITTA ** _b_, Kirby. _Gen. Char._: HEAD transverse, flattish, scarcely so wide as the thorax; _ocelli_ in an open triangle on the vertex, which is flat; _antennæ_ short, filiform, geniculated, scape quite or more than half as long as the flagellum; _face_ flat, excepting in the centre just below the insertion of the antennæ, where it is protuberant; _clypeus_ transversely lunulate, very convex; _labrum_ subquadrate, very convex, with a central, linear, carinated appendage in front, nearly as long as the basal portion; _cibarial apparatus_ moderate; _tongue_ very acute and delicately fringed with short hair; _paraglossæ_ acute, about half the length of the tongue; _labial palpi_ not quite so long as the paraglossæ, the basal joint very long, the rest decreasing gradually in length; _labium_ about as long as the tongue, its inosculation emarginate; _maxillæ_ subhastate, rather longer than the tongue; _maxillary palpi_ filiform, the basal joint the shortest, second the longest, the rest decreasing in length. THORAX oval, usually pubescent, sometimes glabrous; _prothorax_ inconspicuous, as are the bosses of the mesothorax; _scutellum_ and _post-scutellum_ lunulate, the former convex; _metathorax_ gibbous or truncated, but laterally pubescent even in the glabrous species; _wings_ with three submarginal cells, and a fourth sometimes commenced, the second subquadrate and receiving the first recurrent nervure close to its extremity, the second being received beyond the centre of the third submarginal cell [a slightly different arrangement takes place in some of the species, which will be noticed subsequently]; the _legs_ all setose, but the setæ not very