Frenului of the Lepidoptera. 131 
The retinaculum in its normal form is a process spring- 
ing out of the substance of the costal nervure of the 
forewings, and curling over at the end into a small loop 
or ring; this process is usually thickly covered with 
scales. In those cases before-mentioned in which its 
form is that of a pocket receiving the point of the spina, 
rather than a loop, this pocket is formed in the same way 
from the substance of the nervure, and in most cases it 
also is clothed with scales. 
The fasciculi or bunches of scales which receive and 
hold the spinulz of the female are larger and longer than 
the other scales of the wing, but beyond this they possess 
no distinguishing character. Whilst speaking of these 
we must not forget to notice certain long buxches of hair- 
like scales which are often found associated with this 
organ ; these proceed from the thorax of the insect and 
lie across the spina or spinule, thus probably helping to 
keep them in position. 
We have next to consider the two different purposes 
assigned to this appliance by various observers, namely, 
the holding of the wings in position during repose, or, as 
an alternative, the locking together of the fore- and hind- 
' wings as an aid in flight. With a view to ascertain the 
correctness or otherwise of the first supposition, the spinze 
of several living male specimens of moths were amputated, 
such species being selected as assume a well-marked and 
striking position during repose—Pygera bucephala and 
Sphine ligustrc being amongst those experimented upon. 
In every case the original rest position was again assumed 
by the insect after the operation. 
The behaviour of these insects, having one or both of 
the spine removed, was then observed during flight, the 
movement of their wings being watched as they flew up 
and down before the glass of a closed window. In all 
cases in which one spina only was amputated, a difference 
in the blur of the rapidly moving wings was noticed, the 
wings on the side experimented upon being observed to 
move more independently of each other. These experiments 
being conducted within-doors in order to prevent the 
escape of the insect, the conditions were somewhat un- 
natural, and no very clear idea could be arrived at re- 
specting the actual loss of power of flight resulting from 
the want of one or both spin. It is probable that the 
effect of the wind upon a moth so situated would be very 
