I 
324 Sir Everard Home's farther observations 
to be the result of muscular action, regulated by the will of 
the animal. 
All the six toes are supplied with suckers. 
In the horse fly, the tabanus of Fabricius, the suckers differ 
from those of the blue bottle fly in being three in number, in 
all other respects they are the same. In this fly, when the 
suckers are not used, the two outer ones close in before the 
other, and are only spread out when they are to be brought 
into use. 
In the yellow Saw fly, the cimbex lutea of Fabricius, the 
suckers are differently situated from those of the fly ; they 
are placed upon the under surface of the four first joints of the 
toes, one sucker upon each. These suckers are spoon shaped; 
they are represented in Plate XIX. The exterior part is thin 
and pellucid, but at half their depth they suddenly become 
thicker in their coats, forming a ridge at this part which gives 
the appearance of an inner cup, but this is a deception ; the 
exterior membranous portion is alone expanded on the sur- 
face to which the sucker is applied, and the neck of the sucker, 
forms the vacuum. 
All the six feet have suckers. 
The apparatus which has been described to support the 
animal in its progressive motion, is also applied to other pur- 
poses. In the great water beetle, the dytiscus marginaiis, in 
which there is no appearance of suckers on the under side of 
the feet of the female, they are placed on the three first 
joints of the first and second pair of feet of the male, as is 
shown in Plate XX. ; from which it is evident, that such 
suckers are used to retain the female in the embrace of the 
male. In the male, the three first joints of the feet of the 
