74 ILLINOIS STATE ACADEMY OF SCIENCE 



MYTILASPIS CITRICOLA AND OTHER SCALE 



INSECTS 



Wesley N. Speckman, Elmhuest College. 



Scale insects belong to the family Coccidae, which in- 

 cludes three sub-families: Dactylopinae or Mealy Bugs, 

 Coccinae or Soft Scales, and Diaspinae or Armored 

 Scales. Parthenogenesis occurs in many species of Coc- 

 cidae to a certain extent but it is not so general as among 

 Aphididae. The males, which are smaller than the fe- 

 males, are difficult to secure as they have no mouths and 

 are short-lived. They differ from the females also in 

 having wings with which they move about freely. The 

 female is wingless and, attaching herself to a plant or 

 fruit, secretes a scalelike shield as a refuge for herself 

 and her young, losing in time her external organs and be- 

 coming little more than a protecting shell. 



Coccidae are destructive to fruit trees and fruits, yet 

 they do not multiply as rapidly as aphids do. The fe- 

 male fastens her beak in a leaf or fruit and remains in 

 one place. After secreting a scale which envelopes her, 

 she lays her eggs beneath the scale, where they hatch. 

 The young females settle down near the mother. Some 

 Coccidae give birth to living young which are visible in 

 the body of the mother, as may be seen in the microscope 

 slides which I made two years ago. 



In the Mealy Bug, Dactylopinae, no scales are formed, 

 but usually there is a cottony sac. In the common spe- 

 cies of the greenhouses (Pseadococcus citri) Lutz* says : 

 ''The eggs are laid under the female in a loose nest of 

 sticky, white fibers in such quantities that she is forced 

 to stand on her head in order to feed. ' ' 



Soft Scales are characterized by the Cottony Scale of 

 Maple and some other plants. These scales, if such they 

 may be called, are the thickened surface of the insect 

 rather than a true scale. This mass of cottony material 

 is secreted by the female of Pidvinaria innumerabilis in 

 which to place her eggs. The sticky substance found 

 under the trees is honey-dew secreted by these insects. 



• Frank E. Lutz. Field Book of Insects. 



