a. 



<^>^ ^Nr, ^'%. 



JOURNAL OF VARIATION. 



No. 4. Vol. II. June 15th, 1891. 



THE GENUS ACRONYCTA AND ITS ALLIES. 



By Dr. T. A. CHAPMAN, F.E.S. 

 {Continued from page 31.) 



CRONYCTA {Cuspidia) psi. — Psi is in many respects 

 so like tridejis that having fully described those 

 aspects of that species to which I have paid most 

 attention, psi may be most conveniently treated by 

 noting the points of distinction between them, rather than by 

 going into a fully detailed account of each stage. Psi is the 

 only Acro7iycta of which it has happened to me to meet with 

 the Q^^g as laid naturally by the moth in the wild state. This 

 &gg was found on July 4th, 1888, laid on the upper surface of 

 an oak leaf, the diameter was .97 mm., and the height about 

 .^^ mm. ; it had 51 ribs, of a pale straw tint or almost 

 colourless. An o.gg laid in captivity on a glass slide measured 

 1.03 mm. in diameter and had 50 ribs, other specimens had 

 54 ribs. It is thus seen that the &gg is distinctly larger than 

 that of tridens, and has a larger number of ribs ; in colour (or 

 want of colour) and other characters they are very much the 

 same; in the figures (PI. VIII., fig. i, psi ; 2, tridens) the 

 difference in colouring represents the diiferent method taken 

 by the artist, at different times, to show the glassy trans- 

 parency of the eggs, and does not correspond to any actual 

 difference of tint in the eggs themselves. These two eggs 

 exhibit perhaps more distinctly than any others, what is very 

 obvious in all Acronycta eggs, and is common to all eggs of 

 Lepidoptera so far as I have observed them, viz., that the &g'g 

 contents shrink away from the shell in a very early stage of 

 development, leaving a space containing only a clear fluid 

 between, and the flatness of these eggs leaves this space very 

 evident as a margin round the contents, and in the species with 



