HOW ANIMALS EAT. 
bles, and palpi are reduced to rudi- 
ments, while the maxillz are the only 
useful oral organs. These are excessive- 
ly lengthened into a proboscis, their 
edges locking by means of minute teeth, 
so as to form a central canal, through 
which the liquid food is pumped up into 
the mouth. Seen under the microscope, 
the proboscis is made up of innumerable 
rings interlaced with spiral muscular 
59 
Fig. 22.— Mouth of the 
Horse - fly (Tabanus 
lineola): a, antenne ; 
m, mandibles; ma, 
maxille; mp, maxil- 
lary palpi; 7b, labrum ; 
fibres. The proboscis of the I*ly is a 1, labium, or tongue. 
Fie. 23.—Under Surface of Male Spider: a, 
ce, poison-fang ; b, teeth on interior margin 
of mandible, e; 7, labinm; g, thorax; h, 
limbs; 7, abdomen; Jl, spinnerets; m, 
maxillary palpus; d, dilated terminal 
joint. 
modified lower lip; that of 
the Bugs, fitted both for 
piercing and suction, is 
formed by the union of. 
four bristles, which are the 
mandibles and maxillee 
strangely altered. 
As most of the Arachnids 
live by suction, the jaws are 
seldom used for mastica- 
tion. In the Scorpion, the 
apparent representatives of 
the mandibles of an Insect 
are transformed into a pair 
of small forceps, and the 
palpi, so small in Insects, 
are developed into formi- 
dable claws: both of these 
organs are prehensile. In 
Spiders, the so-called man- 
dibles, which move more 
or less vertically, end in a 
fang; and the club-like pal- 
pi, often resembling legs, 
