74 THE entomologist's record. 



and usually, I fear, showing that the hicmpis pupa has helped to make 

 a meal for the feathered foe ; but sometimes I fancy that the cocoon 

 from which the moth has safely emerged is torn open by the birds, 

 either wantonly, in hopes that the moth may still be there, or more 

 probably to find any other insects that may have sheltered therein. 



There is no doubt that one actually sees all the i'lnpty cocoons that 

 are on those portions of trees that are examined, and after allowing 

 for trees not examined, and especially for those portions of trees 

 examined that are out of reach and out of sight, the total number of 

 cocoons for any one year, placed in the typical manner, cannot be very 

 large. I can hardly believe them to be all there actually are, or to be 

 sufficient to keep the species in existence over a bad year. No doubt 

 the insect flies long distances. I have found cocoons where the parents 

 must have flown several miles, and probably much more, and this, no 

 doubt, will enable a comparatively small number of moths to keep a 

 large district inhabited. In my experience it is rare to find a suitable 

 group of alders without one or more empty cocoons ; equally rare to 

 find more than about half a dozen. The duration of these empty 

 cocoons is very various. They often look very fresh in the second or 

 even the third year, and they entirely disappear in from three to six 

 years, traces occasionally perhaps lasting longer. 



The cocoons are much more easily seen on birch than on alder, 

 as on the latter tree growths of lichen are usually worked into the 

 surface of the cocoon, which makes it homogeneous with the bark. It is 

 common to see empty cocoons that would be quite invisible but for the 

 holes in them, and I once had the luck to see one that had been 

 emptied by a bird, in a spot that I had looked over a week before, and 

 seen nothing ; one on a birch tree in my own garden was similarly 

 emptied by a bird before I saw it. 



I have sometimes fancied that the larvie preferred the south side 

 of the tree on which to spin their cocoons, but I think this is very 

 doubtful, as they occur in all aspects and at all heights, from close to 

 the ground to 20 feet above it (detected in a felled tree). I have only 

 once found a cocoon where it would be submerged during flood, and 

 very rarely on trees whose bases are close to the water. 



The last few trees at the top of a valley, if of the right sort, arc 

 frequently inhabited by C. hicusins, as if the moth first arrived there 

 from a neighbouring valley, or was loth to leave. 



The age of an empty cocoon is difficult to settle, and I at first 

 certainly thought they lasted longer than I now believe to be the case. 

 In two or three instances where I have watched individual cocoons, 

 they have become quite unrecognisable in four or live years, though 

 some traces remain rather longer — a bit of the edge of the cocoon, or 

 the central hollow scooped out of the bark. A recent cocoon is known 

 most certainly by the freshness of the surface of this hollowed portion. 



I once bred a native Herefordshire hen, and hoped to get eggs, 

 but circumstances not being propitious, the moth began on the second 

 evening of her existence to lay infertile eggs copiously. This habit is 

 not uncommon in certain Notodontsand others; a ('.furcnla which I 

 took this summer, hoAvever, did not act in the same way. I found her 

 one afternoon on a willow trunk, and put her in a jar with some 

 willow to lay eggs. In three or four days, however, she only laid 

 some 25 or 30 eggs. I concluded that she must be infertile, and 



