Effects of nutrients, queen presence and juvenile hormone analogues on the production of reproductives in the pharaoh's ant, monomorium pharaonis (L.) (hymenoptera: formicidae)
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Date
2005-04
Authors
Say Piau, Lim
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Abstract
The effects of food supplementation and the influence of the presence of
queen and juvenile hormone~ analogues on caste regulation of the Pharaoh's
ants. Monomorium pharaonis (l.) were studied. Two different food types
(protein and lipid) were tested under different colony conditions to gauge the
effects it has on the production of new reproductives. This particular study aid
not provide a clear answer how food types affect the production of new
reproductives. Proteinaceous foods seemed to have an important role a
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colony's survivorship. In addition, the queen's absence and presence appeared
to have effects towards feeding amongst larvae. Different colony conditions
(queenless and queenright) were also tested and were found to have effects on
food distribution to larvae. Under queenless conditions, larvae were fed more
with readily available food. The absence of fertile queen's suppression
pheromones could have been the reason for such a phenomenon. In the final
part of this chapter, brood arrangements in the Pharaoh's ant were assessed.
Results showed ihat Pharaoh's ants adopt a distinct arrangement of brood
where the older ones were placed on the periphery and the youngest in the
center. The pupae and the prepupae meanwhile were placed in the
intermediate ring of these two. Queen's inhibitory effects were later evaluated
by manipulating the presence of queen's body parts. Colonies containing
dead queen's gaster had significantly lower number of queens when compared
with colonies with queen's thorax. head and whole queens. These body parts
seemed to have anti-suppression effects where colonies produced higher
number of reproductives. Production of male reproductives was inconsistent
throughout the entire experiment and was probably because of its ability to
inseminate more than one female. Juvenile hormone analogues (pyriproxyfen
and s-methoprene) too were tested to ascertain the effects it has on future
reproductives. These two JHAs were impregnated into dried tuna fish (1.0 ~tg/ml
- 5.0 )..l.Q/ml) and were given to queenless colonies. Close inspections sflowed
that pyriproxyfen affected newly emerged reproductives physically. These
queens and males emerged with bulbous wings and demelanized exoskeleton.
Most of these aberrant reproductives died within a week after emergence. Smethoprene
however did not produce such results. Finally, a commercially
marketed ant bait, Bioprene-BM was assessed to observe its effects on colonial
growth and production of new :eprocuctives. Production of queens was
significantly suppressed in treated colonies and colonial growth was significantly
lower. Results from all these findings point to the fact that caste determination in
Pharaoh's ants are under the control of more than one factor and these factors
often inter-react with one another to manifest its results in producing new
rep rod uctives.