The labiomaxillary anatomies of mature larvae of exemplars of the four tribes (Xylocopini, Ceratinini, Manueliini, and Allodapini) of the Xylocopinae were examined and compared with the anatomy of the same region on the larva of a generalized, cocoon-spinning Apinae. The exemplars of the first three tribes listed all have the opening of the labial gland on the hypopharynx close to the opening to the pharynx rather than at the apex of the prementum as in the Apinae. Furthermore one of the exemplars of the Allodapini (Allodape ceratinoides Gribodo) agrees in this respect with the three other tribes. However, the other allodapine exemplar (Macrogalea candida (Smith)) has the opening at the apex of the greatly modified labium. Numerous preserved specimens of this species exhibited a conspicuous amorphous, presumably postmortem discharge from the labial gland, suggesting that in this species the labial gland had taken on a new, unknown function compared with other xylocopines (none of which spin cocoons). The study concludes that the hypopharyngeal position of the opening of the duct from the labial gland, far from the premental apex, is a strong larval synapomorphy of the Xylocopinae because it is found in exemplars of all four tribes of the subfamily and has not been reported elsewhere among bees. Although the mature larva of Macrogalea candida has the labial gland opening close to the labial palpi in front of the hypopharynx and therefore presumably on the prementum, the greatly modified labiomaxillary region and the evidence that the gland discharges large quantities of a secretion suggest that the position of the opening is autapomorphic.