T. BISTORTATA, T. BIUNDULARIA, AND ITS VAR. DELAMERKNSIS. 277 



A description of the ova and larvae of T. bistortata, T. biundularia 



and its var. delainerensis, and some further notes on their 



interbreeding. 



{Concluded from p. 246). 

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



Mr. Hewett kindly sent me ova of T. biundularia and its var. 

 ddamert'iixia, from the York district. Those of T. biundularia were 

 laid on May 14th, and hatched on June 3rd and 4th. They, too, 

 are oval, with slightly broader base, smooth and pale yellowish-green. 

 The averge length of the long axis is -698 mm. ; of the short axis 

 •5 mm. I could find no constant difference in the structure and 

 markings of the larv^B from those of T. bistortata. There is a similar 

 great variation in intensity of colour and markings, but this brood 

 seemed darker, as a \\^hole, than the 1st brood of T, bistortata, and 

 corresponded in this respect with the 2nd broods, especially that from 

 captive parents. The average length of the larva is from 3 '25 to 3'5 

 cm. (1" 3'" to 1" 4'"), very rarely 3-65 cm. (1"5"'). The period 

 between hatching and pupation was 32 to 34 days (.June 3-4th to July 

 5-7th). The ova of var. delamerensis hatched on May 30th and 31st, 

 and the larvae pupated from July 5th to 8th, a period of 36 to 39 

 days. All the larvre previously described, as well as most of the 

 var. delamerensis, were kept indoors under similar conditions. I 

 sleeved a few dozen of the latter on oak, exposed to S.W., during 

 the first few days of June, and as the Aveather was continuously 

 fine and warm, there could not have been much difl'erence in the 

 conditions ; but by June 29th I found they had fed sparingly, and 

 were advanced only as far as stage 2. I removed them indoors and 

 fed them on sallow, as I did all the others. They fed up rapidly, 

 and pupated between July 18th and 20th, a period of feeding of about 

 50 days. I cannot but attribute the difference mainly to the influence 

 of the food. A description of the larv* of var. delamerensis corresponds 

 with that of T. biundularia— the brood as a whole was darker and 

 with more intense markings than the 1st brood of T. bistortata. 

 The length, when full grown, averaged 3-25 to 3-5 cm. (1" 3'" to 1"4"'). 

 The result of my observations in 1897 corresponds generally with 

 that of 1896, except that, owing to the insects all emerging earlier, 

 ova were deposited and hatched a month sooner this year. In 

 response probably to this cause and a cooler summer, the period 

 during which the larvae fed was lengthened, and scarcely diflered 

 with any of the insects, extending from 45 to 60 days. Some ova of 

 a Perth T. bistortata, for which I am indebted to Mr. Hewett, hatched 

 on May 17th and 18th, 1897, and pupated June 16-23, a period of 

 only 30 to 36 days, influenced probably by season and temperature. 

 The hybrids fed up in 41 to 46 days. 1 found a similar difference 

 in the size of the ova to that noticed in 1896 — the larger size of those 

 of T. bistortata (1st brood) seems a constant character, Avhich has 

 been corroborated by other observers. The ova of the 2nd brood 

 are also somewhat larger than those of T. biundularia. The ova of 

 the hybrids of the 1st generation followed the size of those of the 

 2 parent, whilst the ova of the 2nd generation are smaller, showing 

 a long axis of -649 mm. and a short one of "465 mm. ; or approxi- 

 mately one may put the relative size in a proportion — ova of 



