What They Are. -An Insect is an animal wliioli, in 

 the adult stage, has its body divided into three distinct 



* regions : the head, the 

 thorax and the abdomen 

 (Fig. lia+). The head 

 bears one pair of anten- 

 nse, and there are always 

 three pairs of legs and 

 usually either one or two 

 pairs of wings attached 

 t ) the thorax. By these 

 characteristics one can 

 usually readily distin- 

 guish an adult Insect 

 from any other animal. 

 Among the near relatives 

 of Insects in the animal 

 world are the cray-flsh, 

 sow-bugs and crabs, but 

 these are mostly aquatic 

 animals, breathing by 

 true gills; they have two 

 pairs of antennse, and at 

 least five pairs of legs. 

 Centipedes, or "hundred-legged worms, "and millipedes, 

 or "thousand-legged worms," are also nearly related to 

 Insects, but they have the thorax and abdomen forming a 

 continuous region, witli from (!to200 segments, each bear- 

 ing oiii- Ml I ,, ,, |,,ii,'^ r,r 1, ^.- : iliiv have one pair of anten- 



the 



ders. In; .- ;imong the Insects, but 



they f"r III .1 ; I I iiM I . Ill ^ ^ .:t I iM \ liave the head and thorax 

 grown tugi-ilici , 111, auii-iiiui-. uud have four pairs of legs. 

 How They Are Constructed.— Insects are constructed 

 on an entirely different plan from the higher animals. 

 Their supporting skeleton is outsidi-, it being simply 

 the skin hardened more or less li\ n Ii.mh. ui>~i;iiirf, 

 known as chitin. This firm outir : ■ ! '. i. .i, mi|. 

 ports and protects the muscles, i i , r\i -, 



and other organs within. Tlir u,^ mr 



and eyes of an Insect are attachul L" ii:> li,_cui, aial all 

 are exceedingly useful organs, as will be shown later in 

 discussing the feeling and the other sensations of an 

 Insect. An Insect's wings and 

 legs are always borne by the 

 thorax. The wings are primarily 

 organs of flight, but are used as 

 musical organs by some of the 

 grasshoppers and crickets. Fe- 

 male canker-worm moths, bed- 

 bugs, and some other Insects 

 have practically no wings, and the 

 house-flies, mosquitoes, male 

 bark lice, n-i.l sM.iil-n- lnsf.,.t.. 

 have but on. ..r ,> i,,., i ,, 



sects use 111- ■ . ;,■ :i , . i. 



walking, m. ■ .i - i ,■ n ■ ; 



o t th I It 



r ch col I I i 1 o 



system of tul 1 k a e a 1 h h 



the blood s confined and through wh h t H n 

 There a o call d heart abo e tl e foo 1 an 1 1 g 

 the m d 11 1 t 1 1 k t a t be n g f 



ever II at ng w th eacl 1 1 



w th tl 1 lar op n ng 11 U i 



fo I nto the head wh s 



cap n 1 I It 1 en fl s o all I ts of 



the 1 o 1 t t the appendag n regular 



trea n wh h ha e dehn te d re t I ut wh h a e 



not confined n tube They 1 ke the o ean currents 

 a e 1 hn te strea ns w th 1 qu d shore Insects do not 

 b eathe through the mouth as man> uppose I ut 



1 la f h I 1 n th 1 of th 1 d} 



Ih open ng or sp 1 1 ad n a > te of a r 

 tubes calle 1 tra hefe The e trachete branch and finally 

 ram fy all throu h the In e t Insects have no 1 ngs 

 b tl e t a 1 eaa on e n e connect w th a a r 

 bladder n the 1 o 1 h h help to buo p tl I t 

 when fl g Tl us the r lat on 1 etween tl 1 n 



of the I lood an 1 e p at on s not nearly o 

 I t I In e ts the a r s a 1 11 



tl fill the trachese an 1 1 lid 



llll I Jtlwlelll 



I III I matte 1 p It In 



I d r t d Aq a 1 t 



fled fore 



Showing the great eye. food ; others \ 

 A detail of a part of for j 

 the snrface of the luis 

 compound eye is alsi 



itlier Insects for i II t I tl 1 tl us 



I hind legs fitted I e i fled Mo e than 4 000 d ffe ent us le have been 

 fount a ngle aterp liar Notw thstand ngthe rdel 

 cate appearance, these muscles are really very strong and 

 their rapidity of action is wonderful ; in certain gnats the 



culiar. The aliment.M.N ..r |. 



tube, oarn|.viiig tin. .•cntr-,! |i.iri i 

 of the I.chIv; in ;i.iult Ins., -Is i; 

 usually iiiuch Inngi-r flniTi the IhmI 

 and is" more or less folded; fn.ili 

 the mouth the food passes through 

 a pharynx, an esophagus. 



"'^Wislirs^ 



ach. 



nerve cords extend fru 

 another ganglion orne 

 head; two nerve cords 



1137. The lour stag 



food canal to 

 ver part of the 

 udinally along 



^^-i^mM 



-IV, 



Egg much enlirged others 



muscles raoveor vibrate the wings 15 000 times per second 

 Then Seii^atiniii -Insects cnn see feel hear taste 

 and smell and the-i m-\\ il i p sess other senses, as a 

 sense of (lirf(ti n "\1 iin In t h i-s e two kinds of e-ses 

 On each siiU nt thi li i I tli I i mpound eye is easilv 



recognized (l-i^ 11 i li nq uiid e^ e is composed 



