78 VARIATION IN EUROPEAN LEPIDOPTERA. 



in rearing larvae are perhaps more competent judges than myself, when 

 I state my disbelief that change of diet is generally so potential a 

 cause of aberration in the imago as many naturalists think. It may 

 perhaps be a remote cause of tendencies which by inheritance become 

 intensified into a decided character, but we have not many data to 

 go upon. Who can say what other terrestrial conditions may not have 

 equal potency ? There are, however, some species which show some 

 immediate results from a change of food, not only in the larva but 

 the imago ; as is, I believe, the case with Abraxas Grossulariata. 

 And in some very variable species of Geometers, notable phenomena 

 present themselves occasionally. For instance, in the cabinet of the 

 Rev. Joseph Greene, there is a bred specimen of Cleora Lichenaria 

 which he fed on the well-known orange lichen of our walls, with the 

 result that the imago is variegated with orange blotches. But I 

 consider this and other instances which occur among such species as 

 display themselves with outstretched wings on walls and tree trunks 

 when at rest, are merely examples of the adoption of protective 

 colouring, assimilating the pattern to the object upon which the 

 insect is in the habit of resting, as, for instance, Hypsipetes Elutata 

 when found on heathery tracts, which loses the leaf green of the 

 sallow feeding type, and adopts a more protective colouring. Let 

 me commend to your study, too, the gradations of tone observable in 

 Gnophos Obscurata taken on chalk, limestone, clay, and darker soils, 

 as it deepens from the whitish grey ' Pullata ' to a sombre speckled 

 black. In such a case, have the mineral constituents of the soil 

 affected the insect indirectly through the medium of its food ? or has 

 the obscure and mysterious law to which I have referred affected the 

 insect directly ? With regard to experiments made to test the whole 

 question, I may be permitted to suggest that it is not likely that 

 polyphagous feeders such as Arctia caja, which is accustomed to a 

 varied diet, would be affected so much as those of more restricted 

 appetite. It seems to me, too, that the silkworm of commerce might 

 contribute to our stock of information on this subject. Domesticated 

 for centuries and fed on two different species of mulberry, and also 

 in this country on lettuce and other fohage, it would be interesting to 

 know whether its colour or pattern has changed. Already we 

 perceive that it seems to have lost the habit of flight in both sexes, 

 and in the lapse of time perhaps would become entirely apterous ! 

 The colour of the silk is said to be affected by the use of certain 

 foliage, but I cannot vouch for the fact. 



Lastly, excess of food seems more likely than variety to produce 

 divergence, if we are to judge from experiments made in other fields 

 of nature ; and it might be worth while trying the effect of rank and 



Naturalist, 



