8 
THE COI.ORADO EXPERIMENT STATION 
the last one. Much careful observation has not rewarded us by the 
finding of a single sexual male or female or an egg of this louse 
out of doors upon an apple tree under normal condditions. 
Professor F. V. Theobald, of the South-Eastern Agri¬ 
cultural College, at Wye, England, in his “Report on 
Economic Zoology,” 1907, says: “The egg stage takes 
place close to the base of the tree, always, however, above ground 
level. These ova remain frequently hidden in the crevices of the 
bark all the winter, and in spring they produce a larva which soon 
matures into the ‘mother-queen’ form, and which sets to work at 
a great rate to produce viviparous young.” Whether Professor 
Theobald is reporting his observations or is reasoning from analogy 
we are unable to say. We know from the actual observations of 
the writers and by Mr. L. C. Bragg, that such a method of pro¬ 
cedure is pursued by the elm woolly aphis, Schiso^teura ameri- 
cana. The fall winged lice of this species that give birth to the 
sexual forms sometimes accumulate in thousands about the bases 
of elm trees to deposit the sexual forms, but we have been unable 
to discover such a habit for the woolly apple aphis. We are not 
averse to believing that it has such a habit, but we have not been 
able to discover it and do not feel sure that Prof. Theobald in¬ 
tended to announce that he had for this species. 
During the winter of 1906-07, when the thermometer barely 
reached zero in the Grand Valley about Grand Junction, and only 
reached —9.3 degrees at Fort Collins, the lice lived over winter in 
large numbers upon the trunks and branches. As a result, in the 
Grand Valley especially, this louse was the most numerous the fol¬ 
lowing spring and summer that we have ever known it in the state. 
Fortunately, the lady beetles (Plate II, Figs. 12, 13, 14, 15) aphis- 
lions (Plate I, Fig. 15), and syrphus larvae, came through in good 
condition, too, so that by the first of August scarcely any of these 
lice could be found anywhere in Colorado above ground. 
Last winter (1907-8) the temperature went several degrees 
lower, and at Fort Collins there were several nights when the 
temperature went below zero, yet quite a number of the little, 
dark, over-winter form of this louse lived through in old scars 
and beneath the dead bodies of the lice of the previous fall. 
Plow many of those that migrate upward from the crowns of 
the tiees in the spring are really from the roots, and how manv 
are the over-winter form from the tops that went down in the 
fall, it is impossible to state with certainty. Tanglefoot bands 
put about the trees early in the spring caught large numbers of 
the ascending lice at the lower margin and apparently the greater 
proportion, early in the season, were the over-winter form. 
