EXTERNAL ANATOMY OF INSECTS. 685 
Armadillus*, and the second the common water-scorpion, 
Nepa. Among the Aptera we find Nirmus, Podura, 
Sminthurus, &c., that belong to this section. 
To the above sections another may be added for those 
insects whose ¢ars? have more than jive joints, which may 
be denominated Polymerous. Here belong the genera 
Gonyleptes, Phalangium and Cermatia. In the first 
the number of joints varies from siz to eleven, and in the 
two last they far exceed that number, amounting in some 
species of Phalangium to more than fifty, and becoming 
convolute like the antennee of Ichneumons °. 
I am next to notice the proportions and shape of the 
tarsus and its joints. ‘The most general law is, that it 
shall be shorter and more slender than the ¢zbza ; but it 
admits of several exceptions—thus, in Megasoma, in all 
the legs; in Diphucephala© in the intermediate, and in 
Amphicoma lineata in the posterior pair the tarsz are the 
longest; in Zrichius Delta these last are longer than the 
thigh and ¢zbza together. In some insects the zarsz are 
disproportionally short, as in Casstda, the Pselaphide, 
Locusta, &c. ‘Though generally more slender than the 
tibia, in several instances they areas thick or thicker, or 
more dilated, as in most of the tetramerous. beetles, 
which being climbers require a dilated tarsus. Again, 
* This is the Dermestes Armadillus of De Geer, (iv. 221—. #. viii. 
Ff. 21—23. placed by Dr. G. Fischer, in a family by itself, which he 
denominates Clambini, Gen. Ins. 52. ad calcem Entomograph. Imp. 
Russ. i.) but which, as Latreille remarks (Fam. Nat. 408), naturally 
belongs to the same tribe as Agathidium, Phalacrus, &c. M. Le- 
clerck de Laval discovered it to be monomerous. Reéegne Animal, 
iil. 365. 
>’ Prate X XVII. Fic. 22. 
© Melolontha sericea and aurulenta. Linn. Trans. xii. 463. 400. 
belong to this genus or subgenus. 
