THE ENTOMOLOGIST. 



Vol. XXIV.] JUNE, 1891. [No. 337. 



STRUCTURE of the TERMINAL ABDOMINAL SEGMENTS 

 IN THE MALES of the GENUS EUPITHECIA. 



By F. Buchanan White, M.D., F.L.S., F.E.S. 



(Plates I. & II.) 



If the hairs which cover the terminal segments of the 

 abdomen of the males of the genus Eupithecia are carefully 

 removed, both the dorsal and ventral aspects of these segments 

 will be found to show certain features which seem to afford 

 specific distinctions. The features in question are due to certain 

 well-defined thickenings of the chitinous material of the segments, 

 and appear as plates which differ in colour and texture from the 

 rest of the segment. I have been able to examine thirty-four 

 species, and in no two species is the structure exactly the same. 



Ultimate Segment: Dorsal aspect. — There is a consider- 

 able difference in the size of the plate in different species. In 

 some (e.g., E. pulchellata, E. castigata, and E. pumilata) it 

 neither reaches the apex nor the sides of the segment ; in 

 others (e.g., E. venosata, E. satyrata, and E. sobrinata) it 

 attains the apex, but not the sides; whilst in a few species 

 (e. g., E. ahsinthiata, E. pusillata, and E. exiguata) it occupies 

 the whole, or nearly the whole, of the segment, as seen from 

 above. The end of the plate is usually more or less rounded, 

 although it is sometimes slightly pointed, as in E. pulchellata^ or 

 truncate, as in E. nanata and E. trisignaria. In a few species 

 the apex is more or less distinctly emarginate or notched. The 

 emargination is very distinct in E. tenuiata and E. ahhreviata, 

 but almost rudimentary in E. dodoneata and E. helveticaiia. 



Penultimate Segment : Dorsal aspect. — The whole, or 

 nearly the whole, of the dorsal part of the segment is occupied 

 by a plate, whose shape is very similar in all the species. 



ENTOM. — JUNE, 1891. M 



