Now, Coccinellidae (ladybirds) are known to be highly distasteful to most insectivorous mammals and birds, and snails would be quite unfit food for the Pompilid or Ichneumonid larvae, so that the reason for the mimicry in these cases is also perfectly clear.
A simple illustration will serve to explain these two aspects of mimicry and to show the advantage in the struggle for existence that mimicry confers upon the species concerned.
Comparatively few cases of mimicry in the Neuroptera have been observed.
It has therefore been suggested by some and taken for granted by others that the resemblance comes under the category of aggressive mimicry and that the ants are deluded by this resemblance into regarding the spiders as members of their own species.
Hence it is probable that this case of mimicry is purely of a protective and not of an aggressive nature and serves to save the flies from destruction by insectivorous enemies.
Coleoptera (beetles) supply instances of mimicry of ants, wasps and Ichneumonids, and some defenceless forms of this order mimic others that are protected.
But if it be discovered, as is possible, that the drone-fly is also inedible, the mimicry must be ascribed to the Mullerian category, and the reason for it becomes less evident.
Since many of the insects of the order Hemiptera are distasteful, the mimicry of the bug (Megapetus) is in this case probably Mullerian or synaposematic; the grasshopper (Myrmecophana), on the other hand, is probably edible and the mimicry is Batesian or pseudaposematic. This is a simple case consisting of a small number of component species.
The second noteworthy phenomenon is the mimicry of more than one protected species by members of a single species.
But since ants are not persecuted by these two families of Hymenoptera, the greatest enemies spiders have to contend with, it is evident that mimicry of ants is of supreme advantage to spiders.