Several species of animal & insect share physical resemblances with other, more dangerous species as a means of defense. 

(Fig. 1) In an example of Batesian mimicry, the non-venomous Mexican Milk Snake (a) bares a brightly-colored pattern similar to that of the venomous Texas Coral Snake (b). Similar forms of mimicry can be seen between several species of common wasps (e) & hoverflies (f). Contrarily, in a demonstration of Mullerian mimicry, the Viceroy Butterfly (c)- once thought of as harmless - is as toxic as the Monarch Butterfly (d), with which it shares a mutually beneficial likeness.

(Fig. 2) Shown is a diagram demonstrating the actual, relative size of each species.