96 M. F. Plateau on the Muscular Force of Insects. 



of species, and the mean weight of each of these species, at the 

 relative values of the strength of insects. From the comparison 

 of these values I deduced the following law : — In the same group 

 of insects, the force varies inversely to the weight — that is to say, 

 that of two insects belonging to the same group the smaller 

 presents the greatest strength. There were, however,, some 

 cases in which this law was not, or only incompletely, verified — 

 namely, when species of the same group differed but slightly in 

 weight : I justly attributed these exceptions to the insufficient 

 number of individuals experimented upon ; for having this year 

 resumed these same trials, doubling the number of individuals 

 (that is to say, raising it to twelve), I found the law above re- 

 ferred to perfectly confirmed, both by the mean relations and by 

 the maximum individual relations, even with species difi"ering so 

 little in average weight as Donacia NymphceiB and Crioceris 

 merdigera, belonging to the group Eupoda. 



I indicated this group of Eupoda as exceeding all others in 

 traction-force. Fearing that this supremacy was only to be 

 ascribed to the stiff" brushes with which, besides the claws, the 

 tarsi of these animals are furnished, and which enable them to 

 adhere with great force to plants, I wished to ascertain whether 

 the Longicorns, which possess the same accessory appendages 

 of the tarsi, also surpassed other insects with simple claws; but 

 both Saperda carcharias and Strangalia armata, with which I 

 experimented on this point, gave me only results analogous, or 

 even sometimes inferior, to those furnished by insects of weights 

 respectively nearly approaching those of these insects, and only 

 possessing simple claws. The supremacy of the Eupoda must 

 therefore be attributed solely to a great muscular force, which 

 is explained partly by the great volume of the posterior femora 

 of those insects, and partly by their small weight. 



I had no time, during my former investigation, to make ex- 

 periments upon the leaping of the Orthoptera. The present 

 note is devoted to this manifestation of muscular force. I have 

 tried what is the maximum weight that these insects can move 

 in leaping. The method employed is nearly the same as that 

 of which I availed myself in the case of flight. I attach to the 

 body of the animal, by means of a thread, a little ball of wax, 

 taking care to make it at first too light, so that it may be easily 

 carried away by the insect. I then increase the weight of this 

 mass, by the addition of fresh portions of wax, until the insect 

 can no longer raise it more than 1 centimetre in height. It will 

 be easily understood that I could not go further; for the real 

 maximum weight would be that which the insect could not raise 

 except to an infinitely small extent, or, in other words, which 

 would fix it to the ground ; and it would have been difficult to 



