umber of Diptera, or two-winged flies, that
closely resemble wasps and bees, and no doubt derive much benefit from
the wholesome dread which those insects excite. The Midas dives, and
other species of large Brazilian flies, have dark wings and metallic
blue elongate bodies, resembling the large stinging Sphegidae of the same
country; and a very large fly of the genus Asilus has black-banded
wings and the abdomen tipped with rich orange, so as exactly to resemble
the fine bee Euglossa dimidiata, and both are found in the same parts of
South America. We have also in our own country species of Bombylius
which are almost exactly like bees. In these cases the end gained by the
mimicry is no doubt freedom from attack, but it has sometimes an
altogether different purpose. There are a number of parasitic flies
whose larvae feed upon the larvae of bees, such as the British genus
Volucella and many of the tropical Bombylii, and most of these are
exactly like the particular species of bee they prey upon, so that they
can enter their nests unsuspected to deposit their eggs. There are also
bees that mimic bees. The cuckoo bees of the genus Nomada are parasitic
on the Andrenidae, and they resemble either wasps or species of Andrena;
and the parasitic humble-bees of the genus Apathus almost exactly
resemble the species of humble-bees in whose nests they are reared. Mr.
Bates informs us that he found numbers of these "cuckoo" bees and flies
on the Amazon, which all wore the livery of working bees peculiar to the
same country.

There is a genus of small spiders in the tropics which feed on ants, and
they are exactly like ants themselves, which no doubt gives them more
opportunity of seizing their prey; and Mr. Bates found on the Amazon a
species of Mantis which exactly resembled the white ants which it fed
upon, as well as several species of crickets (Scaphura), which resembled
in a wonderful manner different sand-wasps of large size, which are
constantly on the search for crickets with which to provision their
nests.

Perhaps the most wonderful case of all is the large caterpillar
mentioned by Mr. Bates, which startled him by its close resemblance to a
small snake. The first three segments behind the head were dilatable at
the will of the insect, and had on each side a large black pupillated
spot, which resembled the eye of the reptile. Moreover, it resembled a
poisonous viper, not a harmless species of snake, as was proved by the
im