| dc.description.abstract | This study was carried out based on the speculation that gradation of hosts as
sources of blood meal by tsetse flies is due to the absence and/or presence of specific
semiochemicals. The study was carried out to establish whether kairomones and/or
allomones from waterbuck Kobus defassa (nonhost of tsetse), buffalo Syncerus caffer
and ox (hosts) emanate from the skin surface of the animals and whether these
semiochemicals are responsible for the relative refractoriness ofthe waterbuck to tsetse
flies.
The behavioural responses of caged individual teneral Glossina morsitans
morsitans on waterbuck and ox and on feeding membranes with and without smears of
different doses of water buck sebum, were compared. No significant difference was
found in the initial landing behaviour on the two animals (waterbuck and ox), nor on
treated and control parts of the membrane. However, the subsequent behaviours of the
flies were significantly different. Whereas none of the flies that landed on the ox
showed any escape behaviour, more than a third of those that initially landed on
waterbuck escaped. Similar results were obtained on feeding membranes treated in part
with the waterbuck sebum. Moreover, flies that landed on waterbuck or its sebum
changed probing sites more often, probed significantly longer and showed a general
delay in initiation of feeding. Comparison of the behaviour of flies that landed on
control zones of the membrane and those on untreated (double control) membrane also
showed significant differences, indicating that the insect's behaviour was affected by a
more volatile chemical signal in addition to a less volatile contact signal associated with
the sebum. Analysis of the waterbuck sebum by gas chromatography-linked
electroantennographic detector (GC-EAD) revealed the presence of two
electrophysiologically (EAG) active constituents of relatively high molecular weights
which may have a role in the close-range/contact effects. The compounds were
identified from their mass spectral data as the diacylglycerol, glyceryll-butanoate-3myristate
and the triacylglycerol, glyceryl I-butanoate-3-hexanoate-2-myristate.
An effective technique for trapping odour from a specific area on the body
surface of a live animal was developed. The odour from the waterbuck body surface
was trapped on various adsorbents including activated charcoal, glass wool and | en |
