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Many ants use pheromone trails to organize collective foraging. This study investigated the rate at which a well-established Pharaoh's ant, Monomorium pharaonis (L.), trail breaks down on two substrates (polycarbonate plastic, newspaper). Workers were allowed to feed on sucrose solution from a feeder 30 cm from the nest. Between the nest and the feeder, the trail had a Y-shaped bifurcation. Initially, while recruiting to and exploiting the feeder, workers could only deposit pheromone on the branch leading to the feeder. Once the trail was established (by approximately 60 ants per min for 20 min), the ants were not allowed to reinforce the trail and were given a choice between the marked and unmarked branches. The numbers of ants choosing each branch were counted for 30 min. Initially, most went to the side on which pheromone had been deposited (80% and 70% on the plastic and paper substrates, respectively). However, this decayed to 50% within 25 min for plastic and 8 min for paper. From these data, the half-life times of the pheromone are estimated as approximately 9 min and 3 min on plastic and paper, respectively. The results show that, for M. pharaonis, trail decay is rapid and is affected strongly by trail substrate.

Faranal (1), the trail-following pheromone of the worker of Pharaoh's ant (Monomorium pharaonis), was synthesized by the coupling reaction of the iododiene 3 with the chiral building block 8 as the key step. The geometrically pure iododiene 3 was prepared by the zirconocene-mediated carboalumination reaction of 2 followed by treatment with iodine.

In an institutional setting in Brazil, the pharaoh’s ant, Monornorium phuruonis was found to be the dominant and most abundant ant present throughout the year. The only other regularly collected ant was the exotic Tupinomu melunoce hufum. However, M. phuruonis dominated bait station visitations, although locally concentrated, wit[ other species restricted to regions in which M. phuruonis was not found.

The immature development of pharaoh's ant, Monomorium pharaonis, workers was studied in a naturally collected Brazilian population. Three larval instars were confirmed by measuring maximal cephalic widths in cohorts of known age. Minimum egg to adult duration was 25 days, while the maximum duration was 54 days, both of which are larger than those reported for European populations. Larval instar development is cyclical at the colony level, suggesting reproductive bursts followed by lower reproductive activity of the queens. Zusammenfassung Larvenstadien und Entwicklung einer brasilianischen Population der Pharao-Ameise, Monomorium pharaonis (L.) (Hym., Formicidae) Die Entwicklung der Pharao-Ameise, Monomorium pharaonis, wurde anhand einer in Brasilien gesammelten Population untersucht. Mittels Messung der maximalen Kopfkapselbreiten wurden 3 Larvalstadien festgestellt. Die minimale Ei-Adulten-Entwicklungszeit wurde mit 25 Tagen ermittelt, wahrend die Maximaldauer 54 Tage betrug. Beide Werte sind groser als die von europaischen Populationen bekannten. Die Larvalentwicklung verlauft im Kolonie-Bereich zyklisch, woraus hervorgeht, das Phasen starkerer Produktionskraft der Koniginnen mit solchen geringerer Produktion abwechseln.

The results from simple choice test experiments with laboratory and field colonies of pharaoh's ants have revealed two behavioural traits that influence the way in which foraging worker ants respond to foods. Initially, worker ants from laboratory colonies showed a distinct preference for certain foods (e.g. honey and peanut butter). However, when given only these ‘preferred’ foods continuously for several weeks, workers showed a marked preference for other foods when offered a choice. This ‘satiation’ response occurred even though the initial diet was originally highly attractive to foraging workers. In addition, workers show a marked tendency to alternate between carbohydrate foods and protein foods. Thus, workers from colonies fed predominantly on proteins, subsequently showed a marked preference for carbohydrates, and vice versa. The ‘satiation’ and ‘alternation’ responses to foods ensure that colonies receive a diet that is both varied and balanced. In addition, these aspects of feeding behaviour have important consequences for the use of food-based baits in control measures against Monomorium pharaonis (L.).

SUMMARY Four isomers of 3-butryl-methyloctahydroindolizine (monomorine 1), a major component of the trail pheromone of Monomorium pharaonis, was tested for attractant and trail-initiating activity, One isomer showed attractancy and, under colony condition, tow initiated trail-following bahaviour. Only the all-cis isomer (monomorine 1a) had both attractant and trail-initiating activity. The results indicated that these compounds may have only limited potential for use in control measures against this species.

(+)-Faranal 1 , the trail pheromone of Pharaoh's ant, was synthesized in 10 % overall yield starting from an easily available chiral building block 2 and employing diastereoselective carbon—carbon bond formation.