694 EXTERNAL ANATOMY OF INSECTS. 
gular with the smaller suckers at the base, and two rows 
of larger oblong ones, concave but not umbilicated, at 
the apex ; in another Brazilian undescribed species (D. 
obovaius K. MS.) the shield is oblong and quite covered 
with suckers like those last mentioned; in Aczlzus sulcatus, 
almost the whole plate is occupied by a very large sucker, 
above which, at some distance in the inner side, are two 
smaller ones, while the extremity of the shield is covered 
by minute ones elevated on long footstalks: the central 
umbilicated elevation of the large one, which nearly fills 
its cavity, is in this species beautifully radiated. ‘The 
male of Colymbetes transversalis has also an orbicular 
shield, but the suckers are much less strongly marked. 
The use of this organ has been before sufficiently ex- 
plained *. 
A few words will be necessary upon the folding of the 
legs in repose. When insects walk, the thigh is usually 
in an ascending position, rising above the horizontal line, 
the ¢2bia forming with it rather an obtuse angle, and the 
tarsus nearly a right one with the ¢ébza ; but in the My- 
riapods, as far as I can unravel their swift many-footed 
motions, these angles in walking do not take place; in 
repose however, in many insects, the coxa forms an angle 
with the thigh below the horizontal line and with the zzbia 
above it, and the ¢idza and tarsus continue in the same 
line, and point downwards nearly vertically ; in others, 
‘as in the Zetramerous beetles, the last-mentioned joints 
form an angle with each other and turn upwards, the ¢zbia 
having an external oblique cavity to permit this ; but the 
insects most remarkable for packing close their legs are 
a See above, p. 304. 
a 
