( xxviii ) 



provided with reproductive organs, and not furnished, like the other stages, 

 with the rostrum. The female lays one egg, the only fertilised egg of 

 the chain. 



The winged form is, I understand, uncommon, or at least difficult to 

 procure in France ; and in England, I apprehend, it is unknown. In 

 Portugal it has seldom, if ever, heen detected, although the insect in 

 its earlier stages is abundant ; and even in the nymph, or pupa stage, 

 it is not unfrequently found, a circumstance which seems somewhat 

 remarkable. 



Perhaps the following notes may be of interest : first, as to the duration 

 of time taken for the transformation from the pupa or nymph into the 

 imago or winged form ; secondly, as to the circumstances which apparently 

 encourage the winged form : — 



Experiment No. 1. — July 13th, 1885, 9 a.m. : Placed a nymph, bright 

 yellow colour, tubercles pink, and clearly defined, in the bottom of a wine- 

 glass on a vine-leaf. Glass covered with fine muslin. Idem, 2 p.m. : 

 Insect could not be seen without moving the leaf, so left it undisturbed. 

 Idem, 5 p.m. : Underneath the leaf was the perfect winged form. This 

 transformation therefore took not more than eight hours. 



Experiment No. Q. — July 14th, 1885, 6 p.m.: Placed a similar 

 nymph on a vine-leaf, under similar circumstances. July 15th, 6 a.m. : 

 Saw the insect on The point of changing. Wings visible. Head and 

 thorax complete, but wings not yet free from exuvia. Idem, 1 p.m.: 

 Wings still not free, but after a few minutes the wings of one side 

 completely cleared themselves, but the exuvia remained obstinately clinging 

 to the wings on the other side. After eight minutes' struggling the insect 

 entirely freed itself; but the wings on the one side remained much 

 crumpled, a circumstance I have noticed in another case, when they 

 remained in this crumpled state for three days, viz., during the insect's life. 

 In the above-mentioned experiment the transformation occupied not more 

 than nineteen hours. 



Experiment No. 3. — Under similar circumstances the like metamorphosis 

 occurred between August '29th, 6 p.m., and August 30th, 9.30 a.m. — that 

 is, not more thdu Jif teen and a half hours. 



Average time from these three experiments about fourteen hours. 



I will now state my experiences (which are, however, very limited) in 

 breeding the winged form in bottles, with a view of suggesting that these 

 experiences, as far as they go, point to a confirmation of what Mr. Buckton 

 has suggested in his ' Monagraph of British Aphides' as the probable cause 

 of the development of the winged form, viz., want of food, and a desire 

 to emigrate. 



My notes on this point will be confined to three bottles only, in wliich 

 I had placed vine-roots plentifully inhabited with PhyUoxerce. Out of 



