Colour, shape and defence in aphidophagous syrphid larvae (Diptera)

Colour patterns, shape and behaviour are analysed in 22 species of aphidophagous syrphid larvae in relation to their possible role in defence against visually hunting predators. Crypsis is the most important method of primary defence. There is much variation in colour pattern. Some species are translucent, others green, brown or otherwise coloured. Most have disruptive stripes, bars or other markings that break up the body outline at short range. There is one example of a bird dropping resemblance. Behavioural requirements for effective crypsis include diurnal immobility, resting in sites that provide maximum concealment, and slow interrupted locomotion. Secondary defences are less variable and involve catalepsis, attack with saliva, and rolling and dropping from the plant.