Smith's observations on _Halictus morio_ in England lead one to infer that there is but one generation, the appearance of which extends over a very long period. He says, "Early in April the females appeared, and continued in numbers up to the end of {25}June"; then there was an interval, and in the middle of August males began to appear, followed in ten or twelve days by females. Hence it is probable that in different countries the times of appearance and the number of generations of the same species may vary. Verhoeff has described the burrows of _Halictus quadricinctus_ with some detail. The cells, instead of being distributed as usual throughout the length of the burrow one by one, are accumulated into a mass placed in a vault communicating with the shaft. This shaft is continued downwards to a depth of 10 cm., and forms a retreat for the bees when engaged in construction. Several advantages are secured by this method, especially better ventilation, and protection from any water that may enter the shaft. The larvae that are present in the brood-chambers at any one moment differ much in their ages, a fact that throws some doubt on the supposed parthenogenetic generation. No cocoons are formed by these _Halictus_, the polished interior of the cell being a sufficiently refined resting place for metamorphosis. Verhoeff states that many of the larvae are destroyed by mouldiness; this indeed, he considers to be the most deadly of the enemies of Aculeate Hymenoptera. The nest of _Halictus maculatus_ has also been briefly described by Verhoeff, and is a very poor construction in comparison with that of _H. quadricinctus_. [Illustration: Fig. 12—Nesting of _Halictus quadricinctus_. _u_, Original burrow, with entrance _e_ thereto; _n_, retreat or continuation of the burrow; _w_, the vaults; _s_, the accumulation of cells. (After Verhoeff, _Verh. Ver. Rheinl._ xlviii. 1891; scale not mentioned.)]