208 SCALE-INSECTS, BARK-LICE, MEALY-BUGS. 
The adult insects are very similar in the different species, 
but the immature scale-like forms show great differences. The 
most common form is very flat, nearly circular in outline, and 
furnished with a beautiful white fringe composed of parallel 
fibers which radiate from the margin of the body. 
None of the species occurring in Minnesota are of any 
economic importance. A few occur on conservatory plants, but 
in the South some species can become numerous enough to cause 
injury to cultivated plants. The insects are readily killed by 
kerosene emulsion, or whale-oil soap. On conservatory plants a 
pyrethum extract is useful on a small scale, and at the same time 
is the cleanest method of killing them. To show how the in- 
sects look the illustration, Fig. 166, of Aleyrodes citri is given. 
FAMILY COCCIDAE. 
(Scale-insects, Bark-lice, Mealy-bugs). 
This large family of insects includes many very destructive 
species, and there is scarcely one kind of fruit free from their 
attack. Until recently scale-insects were rather uncommon, but 
with the wonderful improvement in transportation, such beings, 
both in the form of scales and of eggs, are only too readily 
carried from place to place, from state to state, from continent 
‘to continent. 
The family includes a number of quite different looking in- 
‘sects, as the True Scale-insects or Bark-lice, the Mealy-bugs, 
and others for which we not even have a popular name. They 
are a very anomalous family, and the species differ very greatly 
in appearance, habits, and metamorphoses from the other allied 
families already described. Even the sexes of the same species 
differ as much in the adult stage as do the members of different 
orders. The males, unlike all other hemiptera, undergo a com- 
plete metamorphosis, but possess only a single pair of wings. 
The hind wings are simply represented by a pair of club-like 
halteres, as is the case in the Diptera or Two-winged Flies. 
Each of these halteres is furnished with a hooked bristle, which 
fits in a pocket on the upper wing on the same side. The males 
possess no mouth, but have instead a second pair of eyes. The 
female is always without wings. and has either a scale-like or a 
