EXTERNAL ANATOMY OF INSECTS. 605 
the axis of elytra may be regarded as formed of three 
parts, one appertaining to each of the areas or their re- 
presentatives*; in ¢egmzna, and indeed in wings in gene- 
ral, these parts are separate and may be more distinctly 
traced, the axis of the Costal Area being generally the 
longest, and that of the Intermediate often the shortest; 
these axes are suspended in the wing-socket by elastic 
ligaments, intermixed with hard bony plates, the princi- 
pal one of which, called by M. Chabrier the humerus», 
is connected both with the tegmen and the trunk, and in 
some a little resembles the head and neck of a swan. 
This structure permits the animal to move the lateral 
areas in some degreee separately, so that each, especi- 
ally the anal, shall form an angle with the interme- 
diate; as the motion of the latter is not wanted, its 
axis often falls short of the base, or is obsolete, as in 
Blatta. 
3. Composition. ‘The three areas, traces of which we 
had discovered in elytra, are particularly visible in teg- 
mina. If you take any cockroach (Blatta), you will at 
first sight see that in it they are divided into three larger 
portions by stronger nervures or folds; and if you also 
take a Mantis or Locusta, a Fulgora or Cicada, the 
same circumstance will strike you, only you will see 
that in these the intermediate portion terminates also in 
an axis; these are what I call the three areas. ‘The 
external one or Costal is usually the longest and nar- 
rowest®; the Intermediate one is commonly triangu- 
lar, with its inner side curvilinear’; and the interior 
* Pate X. Fie. 2. is the tegmen of a Blatta divided inte areas, 
b Sur le Vol des Ins. c. ii, 327—. 
© Plate X. Fie, 2. 6. 4 Ibid. ec. 
