FARTS OF INSECTS. 
51 
DEFINITION OF INSECTS. 
^Insects are so called because they are divided into numerous seg- 
‘ ellts j and not from their being almost separated into two parts, which 
e merely attached to each other by a slender thread, as is generally 
supposed. 
All gen u i ne insects have six legs; a head distinct from their body, 
“ n burnished with two antennas or horns; and have pores conducting 
, lrac he* arranged along their sides for respiration : they are all pro- 
duced from eggs. Some undergo no metamorphosis, others but a par- 
tla change, whilst the remainder pass through three stages of exist- 
ence, after being hatched from the egg. 
PARTS OF INSECTS. 
An insect may be divided into four parts. 
1. Caput. 2. Trcscus, 3. Abdomen. 4. Artus. 
CAPUT, the Head, which is distinguished in most insects, is fur- 
nished with Eyes, Antenna, and a Mouth. 
Eyes. Many insects have two crescents or immoveable caps, com? 
posing the greatest part of their head, and containing a prodigious 
number of little hexagonal protuberances, placed with the utmost re- 
gularity and exactness in lines crossiug each other and resembling lat- 
tice-work: these are termed compound eves. 
Leeuwenhoek reckons in each eye of the Libellula, or Dragon-flv, 
12,544 lenses, or in both 25,088; the pictures of objects painted 
thereon must be millions of times less than the images of them pic- 
tmed on the human eye. There is no doubt that insects still smaller 
a\ e eyes adapted to discern objects some thousands of times less than 
themselves; lor so the minute particles they feed on must certainly 
rO l ~.® s * des these larger eyes, many insects have three small spheri- 
a )odies placed triangularly on the crown of the head, called ocelli or 
1 * nmata {Pl. 10 .Jig. 11. J). They are simple, and made for viewing 
ge and distinct objects; the other eyes for small and near ones. 
The antenna; are two articulated moveable processes 
from v* ' Kad : they are subject to great variety, and were the parts 
Setae CC L ' nn6 tormed llis genera': they are called 
Claxuted W i 16n dl0y gtaduu'hy taper towards their extremity; 
Filifor ’ f en ’hey grow gradually thicker from their base; 
Mnntrf ° e 1 u al thickness throughout the whole of their length ; 
beads • ^° rm ' ormt d of a series of knots, resembling a string of 
Oapitate, when they terminate in a knob ; 
