4^^ 





AND 



JOURNAL OF VARIATION. 



Vol. IX. No. 10. October Ioth, 1897. 



A description of the ova and larvae of T. blstortata, T. biundularla 



and Its var. delamerensls, and some further notes on their 



interbreeding. 



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



I have to thank Mr. Mason for a batch of ova of a Clevedon 

 T. bistortata, laid on April 4th, 1896. The ova are oval, with slightly 

 broader base, pale yellowish-green and smooth. The average length 

 of the long axis is -782 mm. ; of the short axis -561 mm. These 

 hatched between May 2nd and 4th, and the larvae pupated between 

 June 14th and 17th, a period of 48 to 46 days. The egg-shell is not 

 eaten by the young larva, and is tenacious and semi-opaque. I have 

 arranged the description of the growth of the larva in four stages, 

 as I found it impossible to satisfy myself as to the different moults, 

 owing to the short periods of quiescence during changing, and to no 

 traces of the cast-oft" skin remaining (with very few exceptions). 

 Probably, however, these stages correspond with the moults. 



The first, or black and white stai/e. — On hatching, the young larva 

 is intense black (in a few, the black is not pure, and there is a trace 

 of grey or brown), with pure white markings arranged in lines and 

 spots, chiefly about the segmental divisions and the spiracles. The con- 

 trast reminds one much of the imago of llelanippe hastata. The white 

 lines are most marked at the fore part of the pro-thorax, meso-thorax 

 and abdl. segt. 1. The most conspicuous spots are arranged in front and 

 behind each segmental division in transverse rows of 4, and on abdl. 

 segt. 6 they form a semicircle with concavity forwards, the outer 

 spots being the largest. The spiracular line is only indicated by 

 large pure white bosses, more or less triangular in shape, about the 

 spiracles. There are three on abdl. segt. 1 ; two on abdl. segts. 2, 3, 4, 

 5 ; three on abdl. segt. 6 ; none on abdl. segt. 7, and one on abdl. 

 segt. 8. There are also a few at the sides of the thorax. Each boss 

 has a darkish tubercle in the centre, with an erect hair. All the hairs 

 on the body are erect and glandular (degenerated), except those on 

 "abdl. segt. 9. These and the hairs on the head are longer, curved 

 and pointed. There is an additional tubercle, making four above 

 the spiracles, besides those described by Dyar in his summary for the 

 family Geometridse. It would appear to homologise with number 

 iii of the middle annulet of the Tenthridinidae, and represent iiia. 

 Those in the white bosses, on abdl. segts. 2, 3, 4, 5, will then represent 

 tubercles iv and v ; those on abdl. segt. 6, tubercles iiia, iv, v. The 



