comment added about 11 years ago by Istvan Miko

Duncan 1939 reported the presence of two stipito-palpal muscles in Vespula pensylvanica, the anterior and posterior depressor of the maxillary palpus. The muscles arise from the median margin and the posterior margin of the posterior stipital sclerite respectively and share one site of insertion on the proximal margin of the first sclerite of the maxillary palp. Snodgrass reported the presence of only one stipito-palpal muscle, however, the site of origin of this muscle extends along the medial and posterior margins of the posterior stipital sclerite, and thus it is possible, that the two muscles in Vespula are homologous with the single muscle in Apis.