ON A RECURRING ABKRRATION OF ZONOSOMA ANNULATA. 239 



On a recurring aberration of Zonosoma annulata. 



By W. S. lilDING, B.A., M.D., F.E.S. 



During the last seven years, I have twice netted in this neighbour- 

 hood (East Devonshire) imagines of Zonosoma aunnlata, which have 

 lost the black ring on the fore-wings, and each year, since 1898, have 

 bred one or more similar aberrations — 10 in all — from larvae collected 

 in the autunui, or their progeny, but I have not been successful till 

 this season in breeding it in any number. 



In September, 1897, I collected larvaj by beating the maple in the 

 hedges over a small area, the same as in previous years, and somewhat 

 less than two- thirds pupated, the rest being stung by ichneumons. 

 The pupae produced perfect insects during the whole of the month of 

 May, 1898, and amongst them were five of these aberrations, all <? s. 

 In three others, the omicron on the fore-wings was very indistinct, 

 though traceable, and four formed a gradation between the latter and the 

 type here, in which the black ring is sharply defined. The aberra- 

 tions were nearly 7 % of the whole brood, and three had the ring on 

 the hind- wings very indistinctly marked as well. 



For description, I shall call the aberration where the omicron is 

 absent on the fore-wings, ab. ohsoleta, and where it is absent on both 

 fore- and hind-wings, ab. bi-obsoleta. The latter is rare, I have only 

 one specimen, though in many the rings on the hind- wings are faint 

 and imperfect, in some there being only a mere trace. 



Some 20 or 30 years ago, Mr. D'Orville took the aberration at 

 Alphington, near Exeter, about 12 miles from Buckerell, and described 

 it in I'l.M.M., but it was not named, and I cannot find any further 

 record since. In his cabinet at the Exeter museum, Z. annidala is 

 represented by five specimens, one of which only is the aberration. 



In previous years, I have both bred insects in which the black ring 

 is imperfectly developed, and captured them flying with a large 

 majority of the type, and their constant recurrence shows that the 

 aberration is persistent and influencing the latter. In ab. obsolcta, 

 the ancestral position of the omicron is recognisable (more easily with 

 a pocket lens) by the paler central scales which persist, though the 

 black ring is lost. 



I paired three of the May aberrations with three typical $ s on 

 May 7th, 8th and 11th. Ova were laid within a few days, and 

 hatched about May 20th, and by June 23rd the larva' had all pupated. 

 The first imago (2nd brood) appeared on June 30th, and the last on 

 July 7th. There were 78 in all, 21 (14 J s and seven $ s), or 27 % 

 were ab. obsolda ; the rest (25 J s, 32 $ s) were typical Buckerell 2nd 

 brood. 27 %, therefore, took after the male, and 73 % after the 

 female parents, and, as one would expect, there were no intermediates, 

 such as I have mentioned above, as met with amongst the insects 

 breeding in the lanes under natural conditions. 



The imagines of the 2nd brood diiier considerably from those of 

 the 1st. They are dusted with black scales over the fore-wings, more 

 sparingly on the hind-wings, giving them a somewhat dusky hue. 

 All the markings are well defined, but the yellowish ground colour is 

 replaced by pale reddish ochre, which is generally difi'used over the 

 whole area of the wings. 



Four of these ab. obsolcta (2nd brood) were paired on June 30th 



