Hilchie 1982 QEv18n1_4 91_126 CC released.pdf - College of ...

102 Hilchie
Evans (1975) reported that cells at the terminal end of burrow galleries averaged about 2.5
times deeper in Colorado populations than in those studied near Albany, New York. Vertical
gallery depths at Empress compare favourably with those at Albany, New York.
If depth of the burrow reflects past evolutionary interactions and with diminished response
to local conditions, presence of shallow burrows in the northern populations may reflect
adaptation to past climatic stress. Cells closer to the surface ought to experience warming
earlier in the season. This permits a longer period of development, which would allow
colonization of areas with a shorter growing season. The opposite may be true in southern areas:
intense heating of the sand by the sun may be lethal to cells near the surface (Chapman et al.
1926) which would select for deep nests.
Data about periods of adult activity were obtained from locality labels; dates were
consolidated into four day units and illustrated in Figure 2 using the area groups illustrated in
Figure 3. Northern populations (Areas 7 to 12) appeared to have one main generation active
during July, and in some (Areas 7, 8, and 9) there appears to be a smaller second generation in
early September. Among southern populations, collection dates range from May 27 to October
17, indicating the possibility of several generations per year.
Data obtained at Empress (Area 12), provide a more unbiased indication of activity of
adults. Collecting dates and number of beewolves collected are both presented so that negative
evidence is an indicator of when beewolves were not present.
Females at the Empress study site appear to occupy nests for a short duration comparable
with Colorado and New York populations (Evans 1975). Evans reports that of 26 marked nests
in Colorado only a few were active after a few days. In the New York Sample of marked nests
(n = 5), two were active three days later (Table 3).
The Empress population is not distinctly different from the New York population. However
Colorado females dig deeper galleries than observed in the two more northerly populations.
Table 3. Duration of nest occupancy on the Empress dunes in comparisons with Evans' (1975)
study sites.
Locality ^s.
Empress, Alberta
Albany, New York
Roggen, Colorado
Day
0 1 2 3 4
15 2 0
5 - - 2 -
26 - - - few
Numbers refer to the nests observed. Day zero refers to when the nests were first
observed.