M. F. Plateau on the Muscular Force of Insects. 97 



know whether this point had not been exceeded. I will add 

 that, in order to obtain the force developed solely by leaping, I 

 always fastened together the wings and elytra, so as to prevent 

 the insect from making use of those organs of locomotion. The 

 mean relations representing the force were obtained, as in the 

 other cases, by calculating the relation between the mean of the 

 weights raised by the individuals of each species and the mean 

 weight of the species. My experiments were made chiefly upon 

 two species of Acridiidse, (Edipoda grossa, and (E. parallela. 

 These species weighed respectively 0*646 gr. and 0*194 gr., and 

 raised a mean weight of 1'064 gr. and 0*638 gr. The propor- 

 tions indicating their relative force are therefore 1*647 and 

 3*288 ; and we see that, in the case of the leaping of the Or- 

 thoptera, we have a further verification of the law according to 

 which, in the same group of insects, the lightest are compara- 

 tively the strongest. 



The difference of structure existing between the Locustidse 

 and the Acridiidse prevented my comparing the great Green 

 Grasshopper [Locusta viridissima) with the above-mentioned 

 Acridiidse; I have, however, made some experiments on the 

 Green Grashopper, and this animal, which is heavier than (Edi- 

 poda grossa, has given me a smaller proportion. 



This fact, with others which will be found in my note, has 

 led me to inquire whether the law according to which the 

 smaller insects possess a more considerable force, instead of 

 being limited to the subdivisions of entomological classification, 

 does not extend to the whole class of Insects. When the twenty- 

 one species on which I have experimented are arranged (for 

 traction, for example) in the ascending order of their mean 

 weights, we find that the series of corresponding mean relations 

 which express the force, although manifesting a tendency to 

 decrease from the lightest to the heaviest insect, nevertheless 

 presents numerous departures therefrom, which must be attri- 

 buted to the differences of structure in the genera in question. 

 But the result is clearly defined if we divide the whole of the 

 species tried into three groups, of which the first contains the 

 lightest insects, the second those a little superior in weight, and 

 the third the heaviest, and take for each of these groups the 

 mean of the relations expressing the forces. This is what I 

 have done. In the first group the weights, all less than 1 deci- 

 gramme, go from 0*015 to 0090 gr. ; in the second the weights, 

 all superior to 1 decigramme, go from 0*111 to 0*540 gr.; and 

 in the third from 0*940 to 1*905 gr. 



As regards flight, the insects upon which I have experimented 

 being all very light, I have only formed two groups of them — 

 that of the species weighing less than 1 decigramme, and that 



