CHAPTER I. 



CHARACTERS OF THE COCCID^B AND COMMENCEMENT OF 

 THE CONSIDERATION OF THE SUBFAMILY DIASPIN^E. 



GENERAL CHARACTERS OF THE COCCID^ AND THEIR RELATIONS TO 



OTHER INSECTS. 



The Scale-insects or Bark-lice, as they are more comprehensively 

 called, constitute a striking group of insects, remarkable for the pecu- 

 liarities of their development. In this family the females never pro- 

 gress to the winged state ; on the contrary, in many of the species, after 

 a short larval period, they undergo a change of form, and retrograde, 

 becoming, when adult, mere living egg-sacks, with organs only of the 

 simplest sorts, such as are needed for reproducing their kind, and to 

 support a degraded, almost plant-like existence. 



The males, on the other hand, advance further and pass through the 

 usual metamorphoses of insects, finally appearing as winged insects. 

 They differ, however, from other insects of the order Homoptera in pos 

 sessing but one pair of wings; the hind pair (halteres) being aborted, 

 and reduced to stumps, which are provided with a hook that grapples 

 the fore- wing, and apparently aids in steadying or directing flight. The 

 existence of the male after reaching the adult state is fleeting ; he seeks 

 out and impregnates one or more females of his kind, and then dies, 

 living at most a day or two, and taking in the mean time no food. In- 

 deed, in this final stage the insect is entirely unprovided with mouth 

 organs or digestive apparatus of any sort. 



Bark-lice commonly excrete a covering, which may be of a horny, 

 resinous, waxy, or powdery nature. Some of these coverings afford 

 products of use in the arts; the white wax of commerce and lac, from 

 which shell lac is formed, are substances of this sort. The dried -up 

 bodies of certain other species yield purple or red dyes, of which the 

 best known in modern times is cochineal. Many of the species, and 

 especially the naked kinds, eject honey-dew, a sweetish liquid, which 

 is greedily lapped up by ants, bees, wasps, and many other insects. A 

 sort of solidified honey-dew, called " manna," is produced by a Bark- 

 louse (Gossyparia mannipara Ehrenberg); it collects in considerable 

 quantities upon the tamarix trees in Arabia, and is thought by some to 

 have been the heaven-sent manna that nourished the Hebrews in their 

 wanderings. Even in our day it is given as food to invalids, and has a 

 limited use in pharmacy. 



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