appears to close the orifice and which I term The 

 Operculum (Macaria clathrata, pi. vhi.}. Surrounding the 

 ostium there may also be a flattened plate, and in the case 

 of the AcidaliincK there is a loose apron, corresponding to 

 the mappa of the male, which hangs over the ostium and 

 which I have named The Instita. 



THE DUCTUS BUKS.E. 



This usually consists of a tube of varying length, lead- 

 ing from the ostium to the bursa. In many cases it is so 

 closely united to the bursa that it is practically impossible 

 to say where the one ends and the other begins, or even 

 to decide whether they are really separate organs. The 

 ductus bursse is often armed with spines (N othopteryx , pi. 

 xxxvii.). 



THE BUESA COPULATRIX. 



This is usually subglobular, and consists of thin chitine 

 which may either be scobinate, or drawn into numerous 

 points forming star-shaped folds on the outer surface. 

 When the latter decoration completely covers the surface 

 I say that the bursa is Instrate (Eupithecia pimpinellata , 

 pi. xxx.), when the surface is only partially covered I 

 speak of the bursa as Pannicular (E. albipunctata, pi. xxx.). 

 When the bursa possesses a distinct hard chitinous patch 

 on the surface I term this patch The Signum. 



THE SIGNUM. Pierce. 



This is an important character and extremely variable. 

 It may be merely a simple scobinate patch or it may be 

 an elaborately spined prominence (Gonodontis bidentata, 

 pi. iv.). A description is given in the text wherever it 

 occurs. 



NOTE. The numbers placed in the text after the specific 

 names indicate the number of mounts, male and 

 female respectively, made of that species. 



