THYSANURA. 55 



figure the mandibles are represented by a continuous line, and the 

 maxilla: by a dotted one. It will be observed that only the tips of 

 these organs project from the cavity of the head. 



There are, as pointed out by Meincrt and by Lubbock, among the Hexapods 

 three principal forms of mouth : 



-t. the mandibulate, in which the mandibles and maxilla: are attached 

 : nally, and are more or less powerful and adapted for biting and chewing. 



ond, the suctorial, in which the mandibles and maxilla: are attached 

 internally, and are not opposite, but parallel, and intended for pricking. 



"Third, the type presented by the Thysanura, in which the mandibles and 

 maxillae are attached internally, and are far from strong, but still have some 

 freedom of motion, and can be used for biting and chewing soft substances. 



The Thysanura includes three sub-orders ; these can be separated 

 by the following table : 



A. With well-developed abdominal legs, insect resembling a Myriapod in 

 form. I. Sv.Mi-in i A. 



A.\. With only six well-developed legs. 



!>. Without ventral abdominal sucker. Caudal appendages bristle-like and 

 many-jointed, or in the form of a pair of forceps. II. CINURA. 



BB. With a bifurcated sucker or tubercle on the ventral aspect of the first 

 abdominal segment. Abdomen with a springing apparatus, or without ap- 

 pendages. III. COLI.KMI:<>I.\. 



Sub-Order I. SYMIMIYLA.* 



This sub-order has been erected for the reception of a single 

 genus, Scofopendrtlla. This genus includes certain minute in- 

 the zoological position of which is in doubt. All of the known species 

 than 7 nun. (.28 in.) in length. The general form of the 

 bod;. ; >les that of a Centipede; and as with the centijn 



ii abdominal segment bears a pair of legs. But except in the 

 once of thesr abdominal legs the structure- of the body is more 

 like that of the Cinura than that of the Myriapods. And the ! 

 live-jointed and end in two i in tin- Cinura; while in the 



;>ula there are six joints, and always a single large claw. 



Sub-Order II. ClNURA.f 

 (Bristle-tails iv >iof/is.) 



Among the pests that annoy th> keeper there is one which 



ingless, but can run rapidly, and which has l,,i 



nphyia: /y (rr< 

 fCinQra >*ra (ovpd), a uiU 



