Class Insecta 535 



start the new colony alone, but must be accompanied by worker bees. 

 This is different from the other social insects. 



Much work has been done recently on communication in bees. 

 Returning workers appear to be able to tell their fellow workers the 

 direction and distance of food by various dances and movements. 



The bees also have another remarkable ability found in no other 

 insects. They control the temperature of the hive. In summer, the 

 workers stand at the entrance of the hive and vibrate the wings rapidly 

 to maintain air movements. In winter the temperature of the hive is 

 raised by their metabolic activity. 



Many biologists consider these social colonies as representing what 

 is known as a "superorganism." Thus the workers constitute the "di- 

 gestive tract," the royal pair or queen the "reproductive system," and 

 the soldiers, the "bodies' defense." Of course, this is an analogy, and not 

 strictly true, but it does emphasize the interdependence of the indi- 

 viduals of the colony. 



ECONOMIC RELATIONSHIPS OF INSECTS 



Insects are impressive as a group not only through their sheer 

 force of numbers but also because of their actual importance in our lives. 

 Many are beneficial while others are distinctly harmful due to their 

 competition with man for food, and also for their role as vectors of im- 

 portant diseases. 



Among the beneficial insects is the familiar honeybee. Since man's 

 early history, this insect has been a domesticated form, important for 

 the production of honey and wax. The silkworm, Bomhyx mori, has 

 also played a major role in the economy of some countries. Lac insects 

 are an important source of shellac. Many bees and other insects are 

 important as poUinizers of food plants; without this activity many 

 fruits could not be produced. Other insects play an important role for 

 the control of injurious species. Most famous of these is the ladybird 

 beetle which feeds on the scale insects that attack fruit trees. 



Many of the most notorious of the harmful insects are those that 

 feed on our crop plants. They do several billion dollars worth of damage 

 annually in destroying crops, forests, and stored grains. Among the 

 crop destroyers are the European corn borer, the Japanese beetle, the 

 cotton boll weevil, the potato beetle, the leaf hoppers, and a host of 

 others. Other insects are pests of domestic animals. These include 

 the horsefly, the warble fly, and the biting lice. Housefiies, mosquitoes, 



