The phenomena, known as "protective resemblance," or similarity to inanimate objects or vegetation, and the kindred phenomenon of "mimicry," or beneficial likeness to certain protected species of animals, are common in the group. In these particulars, considered in their entirety, spiders show a marked contrast to other Arachnida, such as the scorpions, pedipalps, book-scorpions and so-called harvest spiders, which by comparison are remarkably uniform, within the limits of the orders, in structure, habits and other respects.
One interesting phenomenon in spider-life seems to be directly and certainly traceable to this influence, and that is mimicry of ants.
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.
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.
Packard and many others; mimicry and allied problems by H.