188 ^ LEPIDOPTERA. 



without long, posterior veins, then we should expect 

 that this form would have its thoracic rings more 

 cldtsely consolidated. Just such a condition of things 

 is found to exist in the hawk-moth (see p. 208), where 

 the more rapid flight is correlated with greater con- 

 solidation of the thorax, so that the general law ob- 

 served in other insects holds good.^ 



PL IX., Fig. 137, is a view of the thorax of Danais 

 Archippus taken from Edward Burgess's paper on 

 "Contributions to the Anatomy of the Milk-weed 

 Butterfly."^ The prothorax (<^') has its scutum (/) 

 and scutellum (/j-'), episternum (/^'), and prothoracic 

 spiracle (j-'). The mesothorax (^") and metathorax 

 (<^"') are each composed of a scutum (/%/'") and scu- 

 tellum (/r, //), of episterna (/r, Iv') and epimera 

 (/zr, /z/). The point of insertion of the wings is 

 marked by w\ 7v" ; Ip is the shoulder lappet, and ex 

 the coxa of each leg. The abdomen (PI. IX., Fig. 

 135, C) is long and slender. It is composed of eight 

 similar rings which are covered with tiny scales. The 

 scent organ of the male is probably situated near the 

 posterior end. 



The compound eyes (PI. IX., Figs. 136, 140, cy, 

 Fig. 140, ey', cornea of eye) have many facets. The 

 number of these facets varies greatly in the different 

 genera, ranging, according to Mr. Scudder, from about 

 fifteen hundred to four thousand in a square milli- 

 metre. The ocelli are wanting. The antennae (PI. IX., 

 Fig. 135, at; Fig. 134) are thread-like, and knobbed 



1 See also p. 16 for other remarks on the effects of use of the 

 legs and wings; also p. 30. 



^ Annis. Memoirs Bosf. Soc. N'at, Hist., 1880. 



