Mimicry and Warning Colours in Grasshoppers. 127 
perfect in time, as successive casual variations in the 
same direction increased the resemblance. 
The stick-insect is perhaps the most perfect ex- 
ample where resemblance to an inanimate object 
has been the result aimed at, so to speak, by nature ; 
the resemblance of the volucella fly to the humble- 
bee, on which it is parasitical, is the most familiar 
example of one species growing like another to its 
own advantage, since only by means of its deceptive 
likeness to the humble-bee is it able to penetrate 
into the nest with impunity. These two cases, 
with others of a similar character, were first called 
cases of ‘‘ mimicry” by Kirby and Spence, in their 
ever-delightful Introduction to Entomology—an old 
book, but, curious!y enough in these days of popular 
treatises on all matters of the kind, still the only 
general work on insects in the English language 
which one who is not an entomologist can read 
with pleasure. 
A second case of mimicry not yet noticed by any 
naturalist is seen in another grasshopper, also 
common in La Plata (Rhomalea speciosa of Thun- 
berg). This is an extremely elegant insect; the 
head and thorax chocolate, with cream-coloured 
markings; the abdomen steel-blue or purple, a 
colour I have not seen in any other insects of this 
family. The fore wings have a protective colour- 
ing; the hind wings are bright red. When at rest, 
with the red and purple tints concealed, it is only a 
very pretty grasshopper, but the instant it takes 
wing it becomes the fac-simile of a very common 
wasp of the genus Pepris. These wasps vary 
greatly in size, some being as large as the hornet ; 
K 
