THE POPULAR INSECT PLAN 



2o:{ 



except where sensory nerve endings penetrate the armored surface, 

 ending in various sense organs such as compound eyes, antennae, 

 and sensory hairs. 



.epicCar misl cuticulo. 



5P 

 cte 



ermis 



structure- of bocCj^ woJl 

 (.. hair 



chitin.. 



.Cell cf h/podermis 

 basement membrane 



msmbrone •/*^^^ 



•chit 11 



cuticula 



g^^hypodermis «o Chitin in fSlcts or at joints 



some, celts form bains 



The body wall and its modifications. The epidermal portion of the body wall 

 is composed of a horny substance called chitin, the dermal portion having a some- 

 what different chemical nature, like cellulose. In places where movement is 

 necessary the chitin is replaced by a flexible membrane. Several types of hairs 

 are found, some solid, others hollow, all outgrowths of the exoskeleton. (After 

 Snodgrass. ) 



The Head and Its Appendages 



According to the observations of embryologists the head of the 

 bee is made up of six segments that are fused together in the adult. 

 This statement is based on the well-estabhshed fact that every seg- 

 ment in its embryonic condition bears a pair of appendages. Two 

 compound eyes, which are very large in the drones, are placed on each 

 side of the head, while between them in a triangle on the top and front 

 of the head are three simple eyes, or ocelli. Below and between the 

 compound eyes are the jointed antennae. The mouth parts consist 

 of lahrimi and labium, the latter a complicated structure which con- 

 tains the long, flexible Ugula or tongue with a spoonlike labellum used 

 by the bee in withdrawing nectar from flowers. Attached to each 

 side of the ligula are two jointed labial palps. The base of the labium 

 consists of two pieces, the submcntum and mentum. The upper jaws 

 or mandibles are on each side of the labrum, while the lower jaws or 

 maxillae, with their tiny palps, fit closely and laterally over the men- 

 tum. The liquid food, nectar, is first collected by means of the hairs 

 on the ligula, the maxillae and labial palps being formed into a tube 

 through which the ligula works up and down with a kind of pumping 



