92 Introduction to Insects 
[CH. 
In flies the stage after the egg is usually known as 
a Maggot. 
example. 
Those on fly-blown meat will serve as an 
These eventually change into brown packet- 
like bodies known as puparia, pupa-cases or cocoons, 
and it is from these that the adult flies emerge. 
In their first stage beetles are popularly known as 
Grubs. 
The wireworm is one of the best known. It 
changes into a resting pupa stage from which the 
adult beetle is formed. 
We often find insects in one stage only at one 
time so that it is important that we should be able to 
recognize them in all stages. 
The following key gives a rough means of dis- 
tinguishing the three large groups: 
Butterflies 
and moths 
A caterpillar pos- 
sessing a distinct 
head, 3 pairs of 
jointed legs, 1-4 
pairs of false legs on 
abdomen, 1 pair of 
false legs atthe hind 
end of the body. 
; The appendages 
3 |and wings are en- 
Bi cased. The tail is 
” ringed and capable 
of movement. 
Two pairs of 
wings covered with 
scales are present. 
Flies. 
A maggot. No 
legs. No distinct 
head. Anterior end 
narrow, possessing 
a pair of dark jaws 
(some ~ fly larvae 
have distinct heads, 
e.g. leather jackets). 
Entirely enclosed 
in a case or cocoon 
(in the case of the 
leather jacket it has 
no case). 
One pair of wings 
is present. The 
position of the 
second pair is 
marked by “bal- 
ancers.”” 
Beetles. 
A grub possessing 
a distinct head, 3 
pairs of jointed legs 
or none. No false 
legs. 
Appendages and 
wings free. 
Two pairs of 
wings are present: 
those of the outer 
pair are horny and 
do not overlap. 
N.B. The larvae of certain sawflies closely resemble caterpillars but 
they possess more than four pairs of false legs on the abdomen. 
