12 



being rather broader again on the inner margin.' In the broader parts the pale ground 

 colour appears through as spots. Beyond the fascia and parallel to it is a line, often 

 very dark, behind which the space to the fringes is clouded with dark and bisected 

 into two equal parts by a wavy line of the pale ground colour ; the inner portion of 

 these dark parts has below the middle two contiguous short streaks or spots pointing 

 towards the cilia, — a character which no specimen is without. 



" On the posterior wings are similar markings, except the central fascia, which is 

 replaced by a dark cloudy stripe which borders the duller basal portion ; beyond it 

 near the following line and not far from the costa is a black longish punkstrich. 



" The elongate form of the central spot of the posterior wings is well shown in 

 Fischer's figure, and is perceptible in Mr. Hunter's specimen, and the two dark teeth 

 so especially mentioned by Fischer are the most conspicuous markings of the anterior 

 wings ; hence, in spite of Fischer's very different-looking figure, I feel confident that 

 his insect and Mr. Hunter's are the same. 



" Now, how do we account for the insect occurring in London ? One-half of ihe 

 world little knows how the other half lives ; and we may suppose thai one-half of the 

 geometric larvae have little conception of what the other half feed npon. At any rate 

 the tastes of this particular insect are very peculiar. It does not feed on a fungus like 

 our other London friend, Bolelobia fuligiuaria, it does not feed on lichens or moss. 

 On what then ? On the dried plants in collections. 



" We read in Fabricius, Supp. p. 457, ' Habitat in herbariis folia plantarum exsic- 

 catarum exedens. Mus. Dom. Bosc' 



" I supposed Dom. Bosc was anything but pleased at this new collecting ground 

 opened out to him ; but if it be so that a geometric larva finds nutriment in dried 

 plants it is well we should know of it, as a looper casually observed in a herbarium 

 would be supposed to be there quite by accident. 



" On referring again to Fischer we read that ' the perfect insect occurs at the end 

 of July on palings and walls near houses, often indeed in houses, but especially in ware- 

 houses where dried plants are kept, since the larva feeds exclusively on dried plants, 

 and as far as we know never touclies green ones.' 



" It feeds all through winter on these dry plants, and is sometimes very injurious 

 to herbaria, changes in June to a pupa in a slight cocoon in a corner or between dried 

 leaves, and in ten days or a fortnight the perfect insect appears. 



" Now the whole mystery seems explained ; and the occurrence of a devourer of 

 dried plants in Bloonisbury Street, in the immediate vicinity of the British Museum, 

 where perhaps more specimens might be obtained by a careful search, seems perfectly 

 intelligible." 



April 5, 1858. 

 J. O. Westwood, Esq., V.P., in the chair. 



Donations. 



The following donations were announced, and thanks ordered to bo given to the 

 douois:— ' Procucdiugs of the Royal Society,' Vol. ix. No. 2^ ; presented by the 



