In most of the nests of Vespidæ the comb is placed in stages or stories one above the other, and separated by an intervening space, but in many cases there is only one mass of comb. It is the rule that, when the cells of the comb are only partially formed, eggs are deposited in them, and that the larva resulting from the egg is fed and tended by the mother, or by her assistants, the workers; as the larvae grow, the cells are increased in correspondence with the size of the larva; the subsequent metamorphosis to pupa and imago taking place in the cells after they have been entirely {79}closed. The food supplied is of a varied nature according to the species, being either animal or vegetable, or both. [Illustration: Fig. 31—Section of the subterranean nest of the common wasp, _Vespa germanica_, in position. (After Janet.) _a_, One of the chambers of an ant's nest, _Lasius flavus_, placed above the wasps' nest; _b_, root to which the first attachment of the nest was made; _c_, secondary attachments; _d_, the first-made attachment; _e_, a flint within the envelopes of the nest; _f_, the chief suspensory pillar of the second layer of comb; _g_, lateral galleries; _h_, one of the secondary pillars of suspension between two layers of comb; _i_, the layers of wasp-paper forming the envelope of nest; _j_, vacant space round the nest; _k_, flints that fell to the bottom during the work of excavation; _l_, numerous larvae of a fly, _Pegomyia inanis_ (?) placed vertically in ground beneath the nest; _m^1_ to _m^7_, the layers of comb, in _m^2_ the cells are indicated, in _m^8_ (above the main figure) the arrangement of the three cells forming the commencement of the new layer of comb, _m^7_, is shown; _n_, gallery of access from surface; _o_, burrow of a mole; _p_, interval of 90 mm. between top of nest and surface; _q_, height of the nest, 163 mm.]