390 NATURAL HISTORY OF HAWAII. 



coffee aphis,"' the liaiiihdn aphis.''- and the cotton aphis.''-'' oecuiTiiur on cotton, 

 Hihiseus, cucimiber, tare, Portulaca and several other eoninion ])laiits. 



Tlie life history of tiie i)lant-liee is very interesting, hut is exceetlingly 

 complicated. Although it differs somewhat in different species, it is always 

 characterized by what is known as an alteration of generations. Thus several 

 broods or generations of a species will appear during the year. Usually the 

 young spring from eggs laid by a female capable of producing fertile eggs 

 without the intervention of males. The females of some species give birth to 

 living young instead of laying eggs. The true males are generally though 

 not ahvays provided with wings, but the true sexual female always has wings 

 which enable her to carry her I'ggs to a distance and establish a new colony. 

 Several wingless broods will follow one amithei- ])artheuogenetically, when in 

 course of time true sex individiuiis will apjicar "' antl mate, and the females go 

 elsewhere to establish new cdlonies. A little study and caleulatinn will show 

 that millions of individuals may result fi'om a single fertilized female in the 

 course of a very few luonths. 



The aphids, as well as many othei' insects, especially the leaf-hoppers, 

 have the powei' of secreting a viscous saccharine substance called hoiu-y-dew. 

 This they deposit on the surface of the leaves and stems of plants. It thus 

 ha])pens that the sugar-cane aphis and the sugar-cane leaf-hopper have been 

 directly responsible for the increase in the production of honey in Hawaii, 

 as the bees are very fond of this sweetish deposit and gather thousands and 

 thousands of pounds of it annually. In fact, the bees gather so nmch of this 

 substance that it has been necessary to give to this class of honey from these 

 islands the distinctive uami> of "Hawaiian honey-dew honey," since honey- 

 dew enters so largely into the comjiosition of the local product. However, 

 algaroba flowers furnish an immense amount of fine-flavored honey that finds 

 a readv market here and elsewhere. 



CHAPTER XXXI. 



IMPORTANT ECONOMIC INSECTS: PART TWO. 



Sc.\LE Insects. 



The family of scale insects ' includes the mealy-bugs and scale-bugs, or 

 bark-lice. Like the aphids, they were practically all introduced into Hawaii 

 with some of the host plants on which they are found. They owe their name 

 to the fact that the females of many species look like oval or rounded scales 

 attached to the bark, stems or roots of jilants. The sexes are very dissimilar. 

 The adult males, though very i-ai'i'ly seen, ai'c ]irovidc(l with one paii' of func- 

 tional wings, the hind pair being i-uiluMentai'y. They have I'ather long an- 



«^ Tn.r„iih'i;i niirantiw. '^ Aphis blimhusce. "' A phis <,os«i/inl. "^ UsiKilly in llie autumn. 



