Depth of penetration of vertebrate skin by phlebotomine sandflies (Diptera: Psychodidae).

The limited knowledge of penetration depth and its relation to Leishmania transmission is reviewed. Labrum length and maxillary dentition of a number of species of phlebotomines are compared. It appears that the labrum of Phlebotomus argentipes, the vector of kala-azar in eastern India, is only just long enough for obtaining a blood meal in normal human skin. More information on penetration depth is needed, and it might possibly be estimated from the length of the labium when it remains outside the skin and contracts. It would be necessary, however, to note the position of the labium which changes in relation to the labrum.