PHYLUM ARTHROPODA 



319 



TraSc 



mouth (/>), with its four triangular lips, regulates the passage of 

 the pollen or honey taken in as food into the true stomach (c.s). 

 The digestive juices se- 

 creted by the walls of the 

 true stomach change the 

 food into chyme. Part 

 of the chyme is absorbed ; 

 the rest of the food ma- 

 terial is forced by mus- 

 cular contractions into 

 the small intestine (si), 

 where digestion and ab- 

 sorption are completed. 

 Undigested particles pass 

 into the rectum (If) and 

 out of the anus. One 

 pair of salivary glands 

 (No. 2) lie in the head, a 

 second pair (No. 3) in the 

 thorax; they pour alka- 

 line secretions upon the 

 food as it is taken into 

 the oesophagus. 



CIRCULATION. - The 

 blood is a plasma contain- 

 ing ameboid corpuscles, 

 but differs from that 



Of most animals since it FlG - 242. -- Respiratory system of worker 



carries very little, if any, 

 oxygen. The dorsal ves- 

 sel or heart (Fig. 241, dv) 

 is the principal organ of 

 circulation. Blood en- 

 ters it through five pairs of lateral ostia, and is forced forward by 

 rhythmical contractions. From the head region the blood finds 



HtTraSc 



VDSp 



honey-bee as seen from above, one anterior 

 pair of abdominal sacs removed and transverse 

 ventral commissures of abdomen not shown. 

 / sf>, III sp, VII sp, spiracles; HtTraSc, Tra 

 Sc, i, 2, 4, 7, 8, 10, tracheal sacs; Tra, tracheae. 

 (From Snodgrass, Tech. Series 18, Bur. Ent., 

 U. S. Dep't of Agric.) 



