134 ORDER HEMIPTERA 



travel rapidly for a day or two, going especially toward the 

 outer and upper branches where they fix themselves, and 

 during successive moults remain attached to leaf or bark 

 until autumn, when the adults mature, completing the life- 

 cycle. 



Diaspinae. — The armored scales (Diasplmp) differ from 

 the preceding forms in that the waxy secretion separates 

 from the body wall and forms an external shield or cover 

 within which the scale insect is enclosed and within which 

 there is some possibility of movements of parts, although 

 the mouth parts are anchored quite permanently in the 

 bark. Classification of the species in this division is com- 

 plicated by the presence of this external scale, although in 

 many species the external features of the scale are a fairly 

 good basis for the recognition of the species. 



A microscopic examination is required to determine the 

 species in many cases. The pygidium (the fused terminal 

 segments of the abdomen of the female) includes the char- 

 acters most often used, as it is highly chitinous so that it 

 holds its peculiar characters even after a long time in a 

 dried state. Specimens kept dry twenty to thirty years 

 may be used for examination. The dorsal surface may have 

 glands that produce waxy secretion forming the scales. The 

 anal opening is also on the dorsal side. 



Upon the ventral surface the vaginal opening is a con- 

 spicuous landmark and ordinarily grouped around this are 

 small spinnerets which appear under the microscope as 

 strongly chitinized circles. There are generally- four or five 

 groups. These groups are named according to their relation 

 to the vaginal opening. The median or anterior group is in 

 front of the vaginal opening and on each side at about equal 

 distances are the cephalolateral or anterolateral group and 

 the caudolateral group. These spinnerets or grouped glands 

 are entirely wanting in the San Jos6 scale. 



The marginal structure of the pygidium takes second 

 place in the determination of species and the number and 

 shape and modification of the lobes are very important. 

 In some cases there are thickenings of the margin that closely 



