PHYLUM ARTHROPODA 



307 



and some distinguishing features of the larger orders will be described 

 later. Finally, the honeybee will be described as an example of a spe- 

 cialized insect. 



140. Periplaneta amerkana, a Cockroach 



Cockroaches are the only order of living insects that have a fossil 

 record extending back into the Pennsylvanian period, 250 million years 

 ago. Other orders of insects existing then have either become extinct 

 or evolved sufficiently to warrant separation into new orders. Cock- 

 roaches have also been conservative in their habits, shifting only from 

 the steaming swamps of the coal age to the steaming jungles and steam- 

 Compound eye 



Prothora-cic notian 

 Labrum 



Antenna 



Co:x:aL 



TrochsLnter 

 Fcnn-ur 



Win^ 



Tib 



la.' 



Ta-rsiLS 



M(Z.tctlhora.c let 

 sternu-m. 



Abdominal 

 sternum 



— Cla.v/ 

 Pulvillus 



10^^ abdominal 

 notum. 



Figure 16.17. \'entral \ iew of the cockroach. (After Comstock.) 



heated buildings of today. They require both moisture and warmth for 

 survival. 



The large native cockroach P. aniericana (Fig. 16.17) is found in 

 greenhouses and institutional buildings. Adults are a dark reddish brown 

 color, 25 to 35 mm. long. Like all cockroaches these have flattened 

 bodies with long legs on which they can run rapidly and escape into 

 narrow crevices. 



1 41 . External Morphology of the Cockroach 



The head (Fig. 16.18) has dorso-lateral compound eyes, anterior an- 

 tennae and ventral mouth parts. The head is usually bent beneath the 

 body so that the eyes actually look anteriorly. The front of the head 

 extends down as a movable upper lip or labrum behind which are 

 mandibles, maxillae and labium (Fig. 16.18) which are suited to an 



