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within the harbourage and faeces were
concentrated within and around the
harbourage. This distribution pattern of
poisoned carcasses and faeces close to
harbourage shows that the insecticide was
transferred to other conspecifi cs.
B. germanica
were exposed continuously to
adults that had just fed on fi pronil bait and
their freshly deposited residues. In this
exposure condition, the mortalities of
healthy adults (males and females) and
nymphs (fi rst and second instars) were 48-
85% and 100%, respectively. The mortality
of adults declined to 15-39% and < 19%
when they were exposed to both the
fi pronil-intoxicated adults and their
deposited residues that had been aged for 6
and 24 h, respectively. For nymphs, the
mortality remained high (> 96%) after 6 h
and declined to 60-89% after 24 h of ageing.
When fi pronil-intoxicated adults were
removed, the mortality of healthy adults
exposed to fi pronil-containing residues that
had been aged for 6-24 h was only < 1.7%,
whereas nymphs still exhibited 33-45%
mortality.
Hyperactivity and convulsion, which
are typical symptoms of neurotoxic in-
secticides, impair the ability of intoxicated
cockroaches to return to their harbourage
after bait ingestion (Buczkowski
et al
.,
2001). In a test arena used to examine the
distribution of fi pronil-intoxicated male
German cockroaches, 27.5% were found
dying inside the harbourage and the
remaining specimens were scattered around
the test arena at an average distance of 53.7
cm from the harbourage (Buczkowski
et al
.,
2001). Earlier Ross (1993) reported a similar
distribution pattern for German cockroaches
fed on abamectin gel bait. This type of
distribution of dying cockroaches contrasts
with slow-acting insecticides, in which a
more concentrated distribution of intoxi-
cated cockroaches and faeces was found
within the harbourage (Buczkowski
et al
.,
2001). Buczkowski and Schal (2001a)
reported that fi pronil-intoxicated cock-
roaches were as attractive as the common
food sources and toxic to young nymphs.
Also, Lihoreau and Rivault (2011) reported
that odours emitted from recently fed
cockroaches attracted other conspecifi cs
over a short distance, presumably because
they acted as short-range volatile cues to
promote the formation of feeding aggregates.
Therefore, although the number of fi pronil-
intoxicated cockroaches in the harbourage
Emetophagy
Buczkowski and Schal (2001a) fi rst
described emetophagy, or the ingestion of
vomitus, as a possible mechanism for the
horizontal transfer of fi pronil bait in cock-
roaches. Fipronil is a fast-acting neurotoxic
insecticide that contains chemicals that
induce vomiting. Emetophagy may also
occur when other fast-acting neurotoxic
insecticides that are emetogenic are used
(Buczkowski and Schal, 2001a).
Regurgitation in German cockroaches
coincides with the onset of paralytic
symptoms 4 h after ingestion of fi pronil bait
(Buczkowski and Schal, 2001a, 2001b).
Buczkowski and Schal (2001a, 2001b)
recovered 4.5% of the ingested fi pronil from
the outer surface of adult cockroaches. Of
this, > 74% was regurgitated from the oral
region during the fi rst 12 h. The remaining
fi pronil was excreted from the anal region
for up to 48 h. Although only a low amount
of ingested fi pronil was regurgitated, the
vomitus appeared to be very attractive and
toxic. A fi pronil-intoxicated female was as
attractive as the standard laboratory diet (rat
chow) when fi rst instar German cockroach
nymphs were given the choice. Most of the
contact made by the nymphs with the
fi pronil-intoxicated females was with the
mouth part (77%) and the remainder was
with the anal region (23%). In this experi-
ment, nymph mortality was < 58% within
12 h. When food was not available, the
nymphs contacted the fi pronil-intoxicated
females 2.7 times more frequently and
consequently > 88% mortality occurred
within 12 h.
The toxicity of the fi pronil-laced vomitus
excreted from intoxicated cockroaches
declines with time (Buczkowski and Schal,
2001b). The authors also found that excreted
fi pronil was most toxic when healthy
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