Friesia XI, 5

- 270-
completely fill the spore cysts. The smallest spore balls eannot contain
many more than eight spores (Fig. 6).
The one-celled hyaline ascospores are elliptic to suballantoid and
smooth, but their surface is viscous, with an easily seen mucous
secretion (Fig. 6). The ascospores measure 2-5 X 4-9 ,um on average
3.6x7.3,um; 84 % with breadth between 2 and 4,um and 77 %
with length between 6 and 8,um. The ratio of length to breadth
is 2.0.
No conidial state was observed.
All measurements were made with the Carl Zeiss Ocular Screw
Micrometer, as deseribed by SKOU (1972, pag. 19).
H a b i t a t : Ascosphaera atra was isolated by KEVIN HACKETT
from larvae of the alfalfa leafcutter bee, Megachile pacijica, covered
with cysts of A. aggregata (SKOU 1975) and from pollen in the gut
of an otherwise healthy leafcutter larva. Further, A. atra was
observed growing on a pollen mass floating on water in a test tube.
n is not known whether the fungus is able to invade the gut, but
all attempts to produce pathological symptoms in leafcutter larvae
by feeding them with A. atra spores and mycelium failed, and the
fungus has never been observed growing in cells of the leafcutter
nests. Thus, no definite statement can be made about its habitat,
but we believe that A. atra may primarily live in pollen collected by
the leafcutter bees.
G r o w t h c o n d i t i o n s : A. atra grows well and sporulates
abundantly on ordinary media, e.g. malt extract agar. Growth and
sporulation are stimulated by 0.2 % yeast extract, and are only
little affected by a pH over the range of 3.0 to 7.5, though the
density of spore cysts per culture area is greatest at pH 7.0-7.5.
The presence of some Penicillium species inhibits the growth of
A. atra.
C u l t u r e No. 974 (NLI) isolated from an alfalfa leafcutter
bee, M. paciiica, Nevada, U.S.A. 1974, as dsecribed above, is designated
the type culture for Ascosphaera atra sp. nov. This culture is
deposited at CBS, Baarn, The Netherlands, with accession No. 524.75.
A subculture is deposited at CMI, Kew, Surrey, U.K., as IMI No.
225010.