THE OLFACTORY SENSE OF ORTHOPTERA 419 



Inside the wall the chitin is lighter in color and near the center 

 usually may be observed a round or oblong transparent spot, 

 the aperture (figs. 20 and 52, Ap). 



b. Internal structure. As in Lepidoptera and Diptera (Mc- 

 Indoo, '18), some of these pores belong to the dome-shaped 

 type (figs. 68 to 70), because the chitin around the aperture is 

 dome-shaped; most of them, however, belong to the hymenop- 

 terous type in that the chitin around the apertures is slightly 

 depressed (figs. 77 and 82), and only occasionally is one (fig. 79) 

 found approaching the coleopterous type, in which case the chitin 

 is deeply depressed. Internally, these pores differ from all the 

 others yet described by the presence of a cavity or indentation 

 (fig. 77, 7) encircling the base of the chitinous cone (fig. 79, Con). 

 In cross-section this indentation resembles two horns which run 

 from the pore canal (fig. 70, Can) outwardly into the pore wall 

 (fig. 67, W); it is sometimes very shallow (fig. 71) and some- 

 times very deep (fig. 84), and since it is nearly always present in 

 the grasshopper, we may regard these pores as constituting the 

 orthopterous type. 



The pore canal (fig. 70, Can) may be short (fig. 72) or long 

 (fig. 67), but in the base of the pseudospines (figs. 15, e, and 84) 

 on the tibia it passes only about one-half the distance through 

 the integument, therefore, causing the pore aperture to be long. 



ment; fig. 33, largest and smallest pore on last abdominal segment; fig. 34A, a 

 pore from cercus (fourth instar) ; fig. 34B, a pore from cercus and fig. 34C, a pore 

 from anal stylet of Blatta orientalis; fig. 35, 2 pores from ovipositor; fig. 36, one 

 of largest pores, smallest and medium-sized hair from metathorax. Figs. 37 to 

 46, groups of pores on middle leg, and figs. 47 to 51, groups on hind leg (figs. 12 

 to 15); fig. 37, no. 1; fig. 38, no. 2; fig. 39, no. 3; fig. 40, no. 4; fig. 41, no. 5; fig. 42, 

 no. 6; fig. 43, no. 7; fig. 44, no. 8; fig. 45, no. 9; fig. 46, no. 10; fig. 47, no. 1; fig. 

 48, no. 2; fig. 49, no. 4; fig. 50, no. 5; fig. 51, no. 6. Figs. 52 to 58, paired pores 

 on legs; fig. 52, pair d on hind leg; fig. 53, pair g on middle leg; fig. 54, pair e on 

 hind leg; fig. 55, pair h on hind leg; fig. 56, pair m on middle leg; fig. 57, 1 of pair 

 i on claw of hind leg; fig. 58, pair./ and a hair on pulvillus of hind leg. Fig. 59, 

 largest and smallest pore on metathorax at a (fig. 15) ; fig. 60, largest and smallest 

 pore at b on trochanter; fig. 61, largest and smallest pore at c on femur; fig. 62, 

 pore on base of pseudospine at e on tibia; fig. 63, pore at /on tibia; fig. 64, pore on 

 base of spine at k on tibia. Fig. 65, 6 of pores in group no. 11 on front wing; and 

 fig. 66, 6 pores in group no. 12 on hind wing. Ap, pore aperture; B, pore border; 

 W, pore wall. X320. 



