PhD thesis

changing the direction of their bodies, they eventually find the main burrow and can easily leave
the nest (Strohm & Linsenmair 1995).
Since the conditions in the brood cells are humid and warm, there is a continuous threat that
pathogenic microorganisms infest the larva or the provisioned honeybees, which usually results
in the death of the larva (Fig. 1.3) (Strohm 2000; Strohm & Linsenmair 2001). To reduce fungal
infestation of the provisioned honeybees, female beewolves lick the prey extensively, which has
been shown to significantly delay
fungus growth or suppress it entirely
(Strohm & Linsenmair 2001). It has
been suggested that the females
thereby apply an anti-fungal
secretion to the cuticle of their prey,
but the chemical nature of the
substances involved has not been
reported yet (Strohm & Linsenmair
2001). Virtually nothing is known
about how the larva itself is protected
against pathogenic microorganisms,
especially during the long and
possibly very dangerous phase of
overwintering in the cocoon.
1.3.3 Behavior of male European beewolves
Figure 1.3: Female European beewolf heavily infested and
killed by fungi in the cocoon.
Male European beewolves establish territories (about 0.25 m 2 in size), mostly in the vicinity of
the females’ nest aggregations, that do not contain any resources for females (Simon-Thomas &
Poorter 1972; Strohm 1995). The males mark plants in their territories with the secretion of a
cephalic gland that they apply to the substrate with a clypeal brush, and they defend the
territories against intruding males in combat flights without physical contact of the opponents
(Fig. 1.4) (Simon-Thomas & Poorter 1972; Evans & O'Neill 1988; Strohm 1995; Strohm &
Lechner 2000; Schmitt et al. 2003). In the field, males can survive for more than four weeks,
although the apparent median life span is usually shorter since emigrations from an observation
site cannot be distinguished from the death of an individual (Strohm & Lechner 2000). A male
can occupy the same territory for several days and up to two weeks (Simon-Thomas & Poorter
1972; Strohm & Lechner 2000). Several pieces of evidence suggest that the cephalic gland
secretion is serves as a pheromone that attracts receptive females to the male’s territory (Evans
& O'Neill 1988, 1991): Females of several Philanthus species have been observed to approach
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