Blow fly head. Stacked macrophotograph of the head of a blow fly (family Calliphoridae). The image shows the compound eyes, the antennae with their aristae (a sensory organ), the maxillary palpi and the mouthparts consisting of the retractable flexible proboscis with an enlarged fleshy tip, the labellum, a sponge-like structure with many grooves (pseudotracheae) sucking up fluids by capillary action. Female blow flies lay their eggs on meat to ensure a plentiful supply of food for their larvae once hatched.