220 CEYPTOCOCCUS FAGI. 



their parents; thus the secretion gradually thickens 

 and spreads over the tree trunk, eventually forming a 

 more or less continuous mass, often attaining a great 

 thickness (fig. 6 a, profile). In such masses one finds 

 the remains of many generations of females. When 

 an insect takes up a separate abode the secretion 

 forms a complete and approximately round sac, such 

 sacs being commonly met with on newly infested 

 trees, or on the branches just above the trunk of a 

 badly infested tree. It is on the trunks of the very 

 old trees (50 to 100 years) that the insects are found 

 in the greatest numbers, and they probably represent 

 the survivors of many generations which have lived, 

 cycle upon cycle, on the same tree. The larvae do not 

 appear to be of a wandering habit, and comparatively 

 few seek the fresh untenanted bark ; the main 

 branches, as a rule, are not attacked to the same 

 extent as the main trunk. Those larvae which wander 

 over the tree are liable to be borne away by the wind 

 or by birds to other trees, and this is probably the 

 means by which fresh colonies are started. 



EXPLANATION or THE PLATES. 



PL A, fig. 2, Vol. I. Insects in situ on beech bark. 



From a photograph. 



PI. LXX, fig. 1. Adult female (dorsal). X 40. 

 Fig. 1 a. Adult female (ventral). X 40. 

 Fig. 1 b. Adult female in the act of extruding an 



egg (profile). X 40. 

 Figs. 2, 2 a. Rudimentary antennas of adult female. 



X 600. 

 Figs. 3, 3 a. Rudimentary posterior legs of adult 



female, x 600. 



Fig. 4. Anal orifice of adult female. X 600. 

 Fig. 5. Spiracle and parastigmatic glands of adult 



female. X 600. 

 Fig. 6. Ovisacs of insects natural size in situ on 



