36 GENERAL ZOOLOGY 



appearance and development. At first it resembles the female, 

 but it soon passes into a. short resting, m pupal stage, beneath 

 a protecting scale, from which it reappears as a two-winged 

 insect with rudimentary mouth-parts. In this form of meta- 

 morphosis the young differs greatly from the imago, and there 

 is a resting pupal stage before the emergence of the imago. 

 Following common usage, we may speak of this as a " com- 

 plete " metamorphosis. The young is called a larva. 



There are more than eight hundred species of scale-insects 

 known, and it is certain that many more remain to be dis- 

 covered and described. Man is indebted to these insects for 

 a variety of products of greater or less value. One of the 

 scale-insects (Ooc'cus cac'ti), found on the cactus in Mexico, is 

 the source of the red coloring matter, cochineal ; to another 

 (Carte 'ria lac'ca), of India, we are indebted for lac. Several 

 species produce waxy substances in use in various countries 

 of the East. The white wax of one Chinese species, formerly 

 much prized, is said to be replaced now by the use of kero- 

 sene. The manna mentioned in the Book of Exodus is prob- 

 ably the secretion of a scale-insect. It is a sweet substance 

 used to-day by the Arabs as food. 



Definition of Hemiptera (Gr. hemi, half; pteron, wing). 

 The insects mentioned in this chapter all agree in possessing 

 a sucking-beak. They are the insects to which the word 

 " bug " is strictly applicable. The order is called Hemip'tera, 

 the word referring to the fact that in some families the ante- 

 rior wings are hardened as a protection for about half their 

 length. Outside of the cicadas and scale-insects the Hemip- 

 tera develop without marked metamorphosis (see Fig. 17). 



