530 The Animal Kingdom 



of mouth parts. Essentially the mouth part is a hollow needle formed 

 by the intimate fusion of the labium, mandible, maxillae, and at times 

 the hypopharynx, each of which is very elongate and slender. The la- 

 bium is heavy and forms a sheath for the strengthening of the needle. 

 All of this complex structure together forms the "beak" which is in- 

 serted into the victim, be it plant or animal, and the juices are then 

 sucked up through the hollow needle. 



The siphoning type of mouth parts is found only in the adults of 

 butterflies and moths. In this, all the parts are much reduced except a 

 portion of each maxilla which is very elongated and united to form a 

 long, coiled tube which can be extended. Through this tube, nectar is 

 sucked into the esophagus. 



Legs. — Although they are not so highly variable as are the mouth 

 parts, the legs of insects do show some specialization. In general, 

 they are comparatively simple and adapted for walking. Some are, 

 however, modified for other uses. These include the greatly enlarged 

 third legs of the grasshopper for jumping, the grasping forelegs of the 

 praying mantis, the swimming legs of the water boatman, the legs 

 of bees which are equipped with baskets for carrying pollen, and the 

 digging front legs of the mole cricket. 



Wings. — The design of the insect's wing is basically very simple. 

 It is but a double flaplike extension of the body wall with supporting 

 fibers or veins between. The variations in structure are to be found 

 chiefly in the vein arrangement and in the texture of the wing itself. 

 Some wing modifications include the heavy outer wings of the beetles, 

 the scaled wings of moths and butterflies, and the leathery outer wings 

 of locusts and grasshoppers. An extreme wing modification is seen 

 in the flies where the hind pair of wings are reduced to tiny projections, 

 hulteres, which serve as balancing organs. 



Sense Organs. — Much of the success of the insects as a group can 

 be attributed to their excellent sense organs. Most forms are well sup- 

 plied with such receptors as eyes, tactile organs, and chemoreceptors. 



Many insects possess both simple and compound eyes. The com- 

 pound eye, as mentioned previously, forms a mosaic image which is 

 of value in detecting moving objects. The simple eyes apparently func- 

 tion only for the reception of light. Not only can insects perceive 

 colors, but some have even been demonstrated to be able to respond 



