PARTS OF INSECTS. 21 



DEFINITION OF INSECTS. 



IxsECTS are so called because they are divided into numerous seg- 

 ments; and not from their beinc^ ahuost separated into two parts, which 

 are merely attached to each other by a slender thread, as is generally 

 Mipiposed. 



All genuine iusccts have six legs; a head distinct from their body, 

 and furnibhcd with two antenna; or horns; and have pores conducting 

 to trachea- arranged along their sides for respiration : they are all pro- 

 duced from eggs. Some undergo no metamorphosis, others but a par- 

 tial change, whilst the remainder pass through three stages of exist- 

 ,ence, after being hatched irom the egg. 



PARTS OF INSECTS. 



An insect may be divided into four parts. 

 1. Caput. 2. Trvxccs. 3, Addomen-. 4. Artus. 



CAPUT, the Head, \\h\ch is distinguished in most insects, is fur- 

 nished with Ei/es, Aiitfnna-, and a Mouth. 



Eyes. Many insects have two crescents or immoveable caps, com- 

 |)Osing the greatest part of their head, and containing a prodigious 

 number of little hexagonal protuberances, placed with llie utmost re- 

 gularity and exactness in lines crossing each other and resembling lat- 

 tice-work : these are termed compoiuid eyes. 



Leeuwenhoek reckons in each eye of the Libellula, or Dragon-fly, 

 12,511 lenses, or in both 2a.08H-. th^ .>ir«M«r«c r.f -KJ^ptc jv^mf^d 

 thereon must be millions of times less than the miages of them pic- 

 tured on the human eye. There id no doubt that insects stil smaller 

 have eves adapted to discern objects some tJiousands ot times less than 

 themselves- for so the minute particles they feed ou must certainly 

 be Besides these larger eyes, many insects have three small spheri- 

 cal bodies placed triangularly on the crown of the head, called ocelh or 

 stemmata {Fl. lO.fg.ll. h). They are simple, and made tor viewing 

 large an.d distinct objects; the other eyes tor small and near ones. 



\NTENNE The antenna; are two articulated moveable processes 

 placed on the head : they are subject to great variety, and were the parts 

 fnjm whence Linne formed his genera : they are called 



Setaceous, when thev gradually taper towards their extremity; 



Clavated, when tliev grow gradually thicker from their base ; 



Filiforrn, of an equal thickness throughout the whole ot their length ; 



Moniliform, formed of a series of knots, resembling a string of 



beads ; 



Capitate, when they terminate in a knob; 



