Food limitation in the fungus‐gardening ant,Trachymyrmex septentrionalis

Abstract 1. Most ants are more like plants and marine invertebrates than other insects because the adults are sessile and the immature stages are motile. 2. This paper reported the results from a field experiment that increased food levels on the fungus gardening ant, Trachymyrmex septentrionalis, which has served as a model system for understanding the complexities of these obligate mutualisms. 3. Food supplementation increased the growth of the symbiotic fungus and this led to an increase in the amount of fungal biomass. The amount of fungal biomass was generally more important in determining the amount of ant offspring than colony size. 4. The results indicate that the population is food limited and colonies may compete for relatively rare fungal substrate. However, competition in this species is not obvious.     

Chimpanzees prey on army ants with specialized tool set

Several populations of chimpanzees have been reported to prey upon Dorylus army ants. The most common tool‐using technique to gather these ants is with “dipping” probes, which vary in length with regard to aggressiveness and lifestyle of the prey species. We report the use of a tool set in army ant predation by chimpanzees in the Goualougo Triangle, Republic of Congo. We recovered 1,060 tools used in this context and collected 25 video recordings of chimpanzee tool‐using behavior at ant nests. Two different types of tools were distinguished based on their form and function. The chimpanzees use a woody sapling to perforate the ant nest, and then a herb stem as a dipping tool to harvest the ants. All of the species of ants preyed upon in Goualougo are present and consumed by chimpanzees at other sites, but there are no other reports of such a regular or widespread use of more than one type of tool to prey upon Dorylus ants. Furthermore, this tool set differs from other types of tool combinations used by chimpanzees at this site for preying upon termites or gathering honey. Therefore, we conclude that these chimpanzees have developed a specialized method for preying upon army ants, which involves the use of an additional tool for opening nests. Further research is needed to determine which specific ecological and social factors may have shaped the emergence and maintenance of this technology. Am. J. Primatol. 72:17–24, 2010. © 2009 Wiley‐Liss, Inc.     

Oviposition and oogenesis in virgin fire ant females Solenopsis invicta are associated with a high level of dopamine in the brain

Abstract. In the fire ant Solenopsis invicta Buren, virgin females are capable of shedding their wings (dealation) and laying haploid eggs. However, dealation and reproduction are inhibited by a queen primer pheromone that depresses the release of Juvenile Hormone by the corpora allata. In an attempt to identify other neural signals that trigger the reproductive system, we measured the effect on brain biogenic amines of separation from the queen. Dopamine in the brain of virgin females increased from 552 ± 42 to 971 ± 65 fMol/brain when reproduction and dealation were stimulated by 15 days of separation. Octopamine and 5-hydroxytryptamine did not change significantly after the separation. Isolated virgin females fed with a tyrosine hydroxylase inhibitor 3-iodo- l -tyrosine mixed in sucrose for 15 days laid significantly fewer eggs and had fewer chorionated oocytes in their ovarioles than females fed with sucrose only. Restoring dopamine biosynthesis by adding l -dopa to the food also restored oogenesis and oviposition. Dealation was not affected by 3-iodo- l -tyrosine or l -dopa. The possible role of dopamine as the neural target of the queen pheromone regarding its potent allotoregulatory effect in other insects is discussed.     

红蚁净防治红火蚁的药效试验

以含1%氟虫腈、植物淀粉、引诱物质及粘附剂等自制的红蚁净(Pyragne)粉剂,在室内测定红火蚁Solenopsis invicta Buren各虫态的毒力。结果显示:红蚁净粉剂对红火蚁工蚁LT50=20.106h、LT90=23.78h,对有翅繁殖蚁LT50=20.951h、LT90=25.64h;工蚁能将红蚁净传递给蛹和卵引起中毒死亡。     

Waste Management in the Leaf-Cutting Ant <Emphasis Type="Italic">Acromyrmex lobicornis</Emphasis>: Division of Labour,Aggressive Behaviour,and Location of External Refuse Dumps

In leaf-cutting ants, the handling of waste materials from the fungus culture increases the risk of infection. Consequently, ants should manage their waste in a way that minimizes the spread of diseases. We investigated whether in Acromyrmex lobicornis, waste-worker ants (a) also perform roles in foraging or mound maintenance, (b) are morphologically different than other ant workers, and (c) are aggressively discriminated by other worker ants from the same colony. In addition, we investigated whether the location of external waste piles minimizes the probability that wastes spread to the ant nest. In the field, we (a) marked with different colours waste-workers, foragers and mound-workers and monitored whether these ants interchanged their tasks; (b) measured head width, head length, hind femur length and total length of waste-workers; foragers and mound-workers; (c) forced field encounters between waste-workers and foragers, and (d) measured the cardinal orientation of the waste piles in relation to the colony mound. Waste-worker ants did not perform other function outside the nest; neither foragers nor mound-workers managed the waste. Moreover, waste-workers were smaller than foragers and mound-workers, and were attacked if they tried to enter their nest using foraging entrances. The location of external refuse dumps also appears to reduce contamination risks. Waste piles always were down-slope, and often followed the prevailing wind direction. The importance of behaviours such as the division of labour, aggressions against waste-workers and nest compartmentalization (i.e., the orientation of external waste piles) to minimize the spread of pathogens is discussed.     

Microclimatic Conditions Regulate Surface Activity in Harvester Ants <Emphasis Type="Italic">Messor barbarus</Emphasis>

This paper analyses the effect of microclimatic factors (internal soil temperature, surface temperature and surface relative humidity) on surface activity of Messor barbarus harvester ants. We selected 44 colonies in an area of Mediterranean grassland near Madrid (Central Spain), which were monitored for activity between March 1998 and September 1999. Results indicate that microclimatic factors are good predictors of colony activation and intensity of activity. Colonies became active above certain critical values of internal soil temperature and relative humidity. For active colonies, surface temperature was the main regulatory factor for worker departure rate, which peaked at around 25–30°C. Worker speed was positively correlated with surface temperature, although the relationship was weaker for large-sized workers. Microclimatic factors were not enough, however, to predict task allocation outside the nest. The explanation for this aspect of ant behavior probably requires the inclusion of biotic factors in the models.