Some species are normally phytophagous, and the vast majority, at any rate, appear to be capable of continuing to exist and reproducing their kind upon a purely vegetarian diet.
With the exception of the Asilid fly and perhaps some of the Longicorn and Phytophagous beetles, which are probably protected Batesian mimics, all the other species constituting the above-mentioned assemblage are, it is believed, Mullerian or synaposematic mimics.
They are exclusively phytophagous.
The phytophagous species are attached to various parts of plants, dead or alive; and the carnivorous in like manner feed on dead or living flesh, or its products, many larvae being parasitic on living animals of various classes (in Australia the larva of a species of Muscidae is even a parasite of frogs), especially the caterpillars of Lepidoptera, which are destroyed in great numbers by Tachininae.