34 tJuly > 



appeared the two projecting warts on the twelfth segment, which (with 

 other circumstances) enabled me to recognise the species — but I pre- 

 sently also noted another change which puzzled me greatly; I took these 

 little larvae to be H. pennaria — a species in which I had never before 

 seen more than ten legs, nor had any one described it with more than 

 ten legs, but now there appeared a pair of undeveloped ventral legs on 

 the ninth segment ; as I have inferred, I certainly did not see these legs 

 previous to the moult, nor do I think they were then to be seen, but 

 what follows makes me wish I had made quite certain : this pair of 

 legs continues through the second moult, becomes smaller after the 

 third moult, and with the fourth moult disappears, the site being marked 

 by a minute eminence, and afterwards by a little horny depressed 

 plate ; and the larva to all appearance has but the ten legs with which 

 it has always been credited. At their fullest development these extra 

 legs are very tiny, still they are plainly enough to be seen, and are 

 more like the rounded ventral legs of a Noetua than the spreading, 

 clinging legs of a large G-eometer ; they have a black ring round them 

 midway, and a circle of tiny black horny points where the usual circlet 

 of hooks is found. 



Both Mr. Buckler and Dr. T. A. Chapman have confirmed my 

 observation from examination of examples which I have sent them, and 

 we are now examining as many species of the large G-eometrous larvae 

 as we can obtain, but so far without finding any evidence of a similar 

 absorption or suppression of a leg once developed. In other species, 

 as, for instance, in Anisopteryx cescularia (Ent. Mo. Mag., vol. xiv, p. 

 113), we find such legs developed after a moult or two, but continuing 

 to the last in the same proportionate size ; on the other hand, many 

 Noctuce when hatched have only two out of their four pairs of ventral 

 legs of full size, but the other two by degrees grow larger, and at last 

 take their full share in walking and holding fast. 



But in this case a pair of legs is developed, is of no use at any 

 time, and, by and by, is again suppressed ; the only thing like it at all, 

 which I can now call to mind, is the appearance of two horns behind 

 the head of the newly-hatched larva of Cerura vinula, which by degrees 

 are absorbed and disappear ; still, this does not seem so strange as the 

 appearance and subsequent disappearance of even an useless limb. 



Exeter: 9th June, 1881. 



