192 Psyche [December 



int. = Portion of digestive system. 



m. = Meron of hind leg. 



post. n. = Posterior nerve trunk of first segment of abdomen. 



ppl., psc. = Parapleura, or exposed lateral end of postscutellum, 



sc"., sc'". = Scuta of meso-, and metathorax. 



scl"., scl'". = Scutella of meso-, and metathorax. 



sp^, sp2. = First and second abdominal spiracles. 



subal. = Subalar sclerite of metathorax. 



tymp. = Tympanum. 



1. Side \'iew of metathorax and base of abdomen of Apatelodes 

 torrefacta (Eupterotidse), showing primitive macrolepidopterous 

 arrangement of sclerities. 



2. Same view of Hemerocaynpa leucostigma (Liparidse), showing 

 second type of tympanum. 



3. Same view of Catocala parta, showing third, or usual Noctuid 

 type of tympanum. The cover, or alula of the hind wing is drawn 

 forward, and the posterior edge is turned back to expose the spir- 

 acle and structures within the tympanum. 



4. Same view of Alypia octomaculata (Agaristidse) . The internal 

 expansion of the fold between thorax and abdomen is indicated by 

 the dotted lines. A strong suggestion of this structure occurs in 

 some Noctuidse. 



5. Same view of Datana ministra. 



6. Tympanum with its principal muscles and nerve connections^ 

 of the Geometridae (drawn from Biston ursaria and Phigalia tited). 

 Only two of the numerous air-sacs are indicated, the one lying 

 ventrad of the nerve, and along which the nerve runs from the tym- 

 panum to the spiracle, and the large double one connecting the 

 tympana. The latter appears ventral in the dissection, which was 

 opened out on the middorsal line, but in fact lies above the diges- 

 tive system. When the dissection is first opened it is normally 

 filled with air and may be the most conspicuous object in the field. 



