CHAP. XX. SCALE-INSECTS. 127 



CHAPTER XX. 



SCALE-INSECTS. 



The Scale-insects, Scale-bugs, Bark-lice, Mealy-bugs, etc., 

 comprise a group of insects belonging to the Sub-order Ho- 

 moptera, and to the Family Coccidse. 



In many respects this is a very anomalous group of insects, 

 differing greatly even from closely allied forms, in appearance, 

 habits, and metamorphosis. Not only do the members of this 

 Family appear very different from other insects belonging to 

 the same Sub-order, but there is a wonderful variety of forms 

 within the Family; and even the two sexes of the same species? 

 in the adult state, differ as much in appearance as insects 

 belonging to different Orders. 



The more striking characteristics in which these insects 

 agree, and by which they may be distinguished from other 

 insects belonging to the same Sub-order, are the following: 

 The females never possess wings; the males are winged in the 

 adult state, but possess only one pair of wings, the second 

 pair being represented by a pair of small club-like organs 

 called " halteres," each of which is usually furnished with a 

 bristle. The scale of the female is usually broader than that 

 of the male in the scale-bearing species. This Family is 

 divided into three Sub-families, as follows: 



SUB-FAMILY I. (Diaspinse). These insects are enclosed or 

 covered by a scale composed in part of the moulted skins 

 (exuvise) and partly of an excretion of the insect; this scale 

 does not adhere to any part of the insect's body, but merely 

 forms a covering or protection for the latter. 



SUB-FAMILY II. (Lecaninae). These insects are usually not 

 enclosed in a scale, but the skin hardens as the insect ap- 

 proaches maturity. In the earlier part of their lives these 

 insects are capable of crawling about, but when near maturity 

 they generally become immovably fixed to the bark, etc.? 

 upon which they rest. 



