104 



ANATOMY OF AN AKTHROPOD. 



tarsals vary in different groups of Arthropods. The first tarsal 

 is sometimes spoken of as the metatarsal (/). 



Abdominal appendages are seldom found in Hexapods : when 

 present, they are never in the form of locomotory organs as they 

 are in Crustacea and Myriapoda. In our type we see only the 

 anal oerci before mentioned. The anus is situated beneath the 

 tenth abdominal tergum and between the podical plates. 



The spiracles (fig. 42, Sp), or breathing pores, are at the sides 



Fin. 40.— Structure of Ikskct Leo. 



i(, Coxa ; h, trochanter ; c, femur ; d, tibia ; c, tibial spur ; /, metatarsus ; 

 g, tarsus ; h, ungues. 



(.Six foot segments occur in the Cockroach.) 



of the thorax and abdomen ; they are twenty in number. On 

 the thorax one pair will be seen between the pro- and meso- 

 thorax, another between the meso- and metathorax, and others 

 on each side of the first eight abdominal segments. They are 

 in the form of slit-like oval openings, with branched processes 

 running across them. 



Infernal Anatomy of ilie Cod-roach. 



By dis.secting the cockroach under water we can gather a fair 

 knowledge of the general anatomy of an arthropod with con- 

 siderable ease. On removing the chitinous covering of the 

 thorax and abdomen very carefully, there will be exposed a 

 .straight chambered tube running along the middle line of the 

 tliorax and abdomen. This is the so-called insect heart. Lateral 



