140 M.F. Plateau on the Muscular Force of Insects. 
which is at first too large for it to move, and is then dimi- 
nished until the insect can barely support it m the air by the 
movement of its wings. 
In these three kinds of experiments the muscular force of 
a species is represented by the relation between the mean maxi- 
mum weight moved individually by a certain number of insects 
of the species in question and the mean weight of the insects. 
The deductions which I draw from the results taken in their 
totality are as follows :— 
1. Leaving flight out of consideration, insects have, relatively to 
their weight, an enormous strength in comparison with Verte- 
brata. Thus, from experiments made with draught-horses, 
these animals, the average weight of which is about 600 kilo- 
grammes, can only exert for a few moments a force of traction 
equivalent to 400 kilogrammes, that is to say, two-thirds of 
their own weight; but I have found that the common Cock- 
chafer (Melolontha vulgaris) and Donacia nymphee exert a force 
equal respectively to fourteen times and forty-two times their 
own weight. 
The pushing led to analogous results; but, in general, the 
weights raised by insects during flight are much less, which 
might be expected, as these little animals have never to trans- 
port considerable burdens through the air, as is done especially 
by the Rapacious Birds*. 
2. The weight of insects and the ratios representing their mus- 
cular force are connected by what appears to be a general law, 
at least according to the numerous experiments that I have made. 
The following is the law, which is clearly manifested both in 
the case of flight, and in those of traction and pushing :—Jf in 
the same group (family or tribe) of insects we examine two species 
which differ considerably in weight, the smallest and lightest will 
exhibit the greatest force ; in other words, in the same group the 
force, always measured by the relation of the weight moved 
to that of the animal, varies from species to species in an in- 
verse ratio to the latter weight. 
In connexion with this I will give a few examples taken from 
the tables of my memoir. These tables contain for each spe- 
cies, besides the mean ratios expressing the force of that 
species, the maximum of the isolated ratios furnished by the 
different individuals experimented on; and the law is manifested 
therein, not only in the mean ratios, but also in the individual 
maximum just mentioned, 
[* M. Plateau seems here to have forgotten the Sand-Wasps, many of 
which carry caterpillars of comparatively large size to their burrows.— 
W.S. Do] 
