SOCIAL ECONOMY. 225 
the larvee were not taken to the larder rather than 
the nursery. 
How the change of position is effected I cannot 
say from actual observation, but, as all the means 
which are at the embryo’s command are sufficiently 
obvious, it is easy to see how only it can be done. The 
larva can lengthen or contract, stiffen or relax its 
body and bend it in any direction, and it has an instru- 
ment by which it can attach either extremity of the 
body at will to any neighbouring object. Obviously, 
by these means it can travel up and down in its cell, 
provided only that each one of the prehensile organs 
be strong enough to sustain the whole weight while 
the other is bemg shifted. And the operation will 
be more rapid and safe, just in proportion as the 
size of the larva gives it a longer step or reach. 
The mandibles are the prehensile organ at one 
end of the body; at the other end this is supplied 
by the peculiar conformation of what we must call 
the legs, though to most people the tail might 
seem the more appropriate denomination. A perfect 
insect has six legs; and, in larvee which have a 
greater number of legs, such as the caterpillar, the 
temporary or larval legs are quite distinct from the 
six rudimentary legs which are to support the insect 
through life in a more highly developed form. The 
true legs of the caterpillar are but claws in their 
embryonic form; and the larval legs are merely oval 
suckers, each surrounded by a ring of bristles. The 
larva of the wasp has but one pair of larval legs, 
which are connected with the last segment of the 
abdomen. And, as the requirements of the wasp- 
embryo demand, these take a form quite unlike that 
