MR. T. H. CORRY ON ASCLEPIAS CORNUTI. 187 
a firm and sure foothold on the unstable flowers, which nod upon their extremely slender 
pedicels. In doing so it keeps up a continual movement with its feet, which cling only 
with very great difficulty to the convex and c«tremely smooth external surface of the 
nectary on which they have been set. The hooked claws of the feet of such an insect, 
being unable to retain their hold on the nectary, are apt easily to glide off this laterally 
into one of the smooth more or less concave valleys which intervene between the par- 
ticular nectary on which it has settled and those which are next adjacent *. This 
concave valley is in its lower part, between the bases of the nectaries, slightly more de- 
pressed. In the centre of this valley runs one of the alar fissures. Into the wider portion 
of this the insect at length places one or other of its feet, and being by this means afforded 
for an instant the firm foothold which it desires, the hooked claws diverge. If the insect, 
however, while it is slipping downwards, sets its foot first on the partially divergent 
grooved margins of the anther-alz, these, being very thin, bend slightly backwards, and 
the foot immediately slips down till it reaches the notch near the lower extremity of each 
(№, figs. 5, 7, 8), where it is arrested and stops. The two fleshy teeth which embrace the 
bases of each pair of anther-alre (m, m, fig. 10) prevent the latter from being bent back- 
wards for too great an extent, and serve in part to cause them again to come together 
externally after the insect's foot has entered the alar chamber through the notch-like 
expansion at its base +. When the insect endeavours to withdraw its foot in order to 
proceed further, or shifts its position ever so little, the divergent claws are easily caught 
by the contiguous opposed borders of the neighbouring anther-ale, and the insect soon 
finds that the only mode of escape is to slip the foot gradually upwards in the channel 
of the alar chamber towards the apex of the flower. Should it, however, endeavour to 
pull its leg out directly, in its effort to do so its leg is frequently caught so fast by the 
gradual narrowing of the channel of the alar chamber, due to the decrease in breadth 
of Ше alæ, that it requires to use all its strength in order to get free, and so it often 
happens that the insect lets go its hold of the flower with all its other legs, and en- 
deavours with its whole strength to extricate and extract that member which is caught. 
This latter phenomenon may be observed frequently and with ease in the case of the 
ordinary Hive Bee (Apis mellifica), but never in the case of the Humble Bee (Bombus 
italicus), since the latter, owing to its greater strength, is able more easily to become 
free, although not without considerable trouble. Very often the insect is unable to 
extricate its foot, and so a leg becomes torn off, and is left behind hanging in the fissure, 
several joints even being thus removed; and yet notwithstanding this the insect, un- 
warned by experience of the danger which it incurs, continues its visits to this perilous 
flower, often greatly to its own detriment. 
The drawing out of the leg is, however, in most cases performed without such violence, 
* [I have never noticed this. The feet of Flies are well adapted to cling -to a smooth surface ; they keep them 
moving about, but I have not noticed them distinctly slip, and in some genera, as in certain species of Piaranthus, 
К. Br. (not of other authors), they could scarcely slip if they tried.—N. Е. Br. } 
+ The anther-alw never diverge from one another to any extent below, as they have frequently been stated to do; 
on the contrary, in the mature flower they are subparallel, except for their slightly grooved extreme margins. The 
mode of entrance into the alar chamber is always at the notch. 
