Abstract. The morphology of all larval instars of Fannia canicularis (Linnaeus)
(Diptera: Fanniidae) is documented using a combination of light and scanning
electron microscopy. The following structures are documented for all instars: antennal
complex; maxillary palpus; facial mask; cephaloskeleton; ventral organ; anterior
spiracle; Keilin’s organ; posterior spiracle; fleshy processes, and anal pad. Structures
reported for the first time for all instars include: two pairs of lateral prominences on
the prothoracic segment; additional ventrolateral prominences on the second thoracic
segment, and a papilla at the base of the posterior spiracle. Other structures reported
for the first time are anterior spiracles in the first instar and a serrated tip on the
mouthhook in the second instar. A trichoid sensillum on the posterior spiracular plate,
representing a sensory organ otherwise unknown in the Calyptratae, is described in the
second and third instars. Results are discussed and compared with existing knowledge
on dipteran larval morphology.