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Optimal foraging theory (OFT) states that animals will forage in a way that maximizes energy intake while minimizing energy expenditure. Eusocial insects are examples of species that exhibit OFT. One type of eusocial insect is the carpenter ant (Camponotus). Carpenter ants use pheromone trails as a form of communication. In using chemical cues to communicate with one another, carpenter ants fulfill OFT by maximizing energy rewards and minimizing energy spent searching for resources. We conducted choice trials with different sugar water concentrations and observed how relatedness between ants affected foraging behavior. We tested if carpenter ants would act according to OFT and forage from the resource with the highest energy reward or if the presence of non-related ants would influence their behavior. We collected ants at Mclaughlin Natural Reserve in California and placed them in an arena with four different sugar water concentrations either with ants of the same colony (sisters; intracolonial) or ants of a different colony (strangers; intercolonial). Our findings supported our hypothesis that the presence of ants from different colonies affects foraging preferences. Intracolonial ants took less time to visit concentrations and made more visits to higher concentrations in comparison to ants in intercolonial trials. We theorize that this may be due to the chemical cues used to distinguish between ants of the same colony and to communicate the presence of sugar water. We also observed that ants had a strong preference for the highest concentration of sugar water, supporting our second hypothesis that ants prefer higher quality resources. We speculate that this is due to optimal foraging theory, where animals seek to maximize their energy intake while minimizing their energy expenditure. The findings of this study highlight the complexities of animal foraging behavior and communication between members of the same species., CEC Research Volume 5, Issue 1

The type of Ophiocordyceps unilateralis (Ophiocordycipitaceae, Hypocreales, Ascomycota) is based on an immature specimen collected on an ant in Brazil. The host was identified initially as a leaf-cutting ant (Atta cephalotes, Attini, Myrmicinae). However, a critical examination of the original illustration reveals that the host is the golden carpenter ant, Camponotus sericeiventris (Camponotini, Formicinae). Because the holotype is no longer extant and the original diagnosis lacks critical taxonomic information – specifically, on ascus and ascospore morphology – a new type from Minas Gerais State of south-east Brazil is designated herein. A re-description of the fungus is provided and a new phylogenetic tree of the O. unilateralis clade is presented. It is predicted that many more species of zombie-ant fungi remain to be delimited within the O. unilateralis complex worldwide, on ants of the tribe Camponotini.

Social insects commonly exhibit division of labor in non-reproductive tasks. Task allocation may be related to size, form, and ergonomic differences when workers are anatomically variable. Carpenter ants Camponotus mus collecting nectar exhibit a wide forager size variation, thus raising the question of whether large and minor workers differ in their gustatory responsiveness and specialize, therefore, on different nectar sources. To answer this question, we first established the sucrose concentration at which small and large ants in the laboratory respond appetitively to a sugar solution (sucrose acceptance threshold, SAT) after experiencing a high or a low starvation regime (4- or 1-day carbohydrate deprivation, respectively). Under high starvation, no differences in SATs were found between larger and smaller ants. Under low starvation, both sizes increased their SATs but larger ants had a higher SAT, thus preferring more concentrated solutions while smaller ants responded mostly to more diluted sucrose solutions. In a field assay in which the distribution of larger and smaller ants on sugary food sources was analyzed, small and medium ants were found—in different proportions—at all food sources while larger ants were only found at nectar sources with a higher sugar flow rate, i.e., providing more sugar per unit time. Both field and laboratory assays supported that sugar-related parameters act as determinants of the size distribution of ants among food sources. In addition, interindividual differences in alternative non-sugar-related variables may contribute to this distribution, leading thereby to a potential nectar foraging specialization. Significance statement: Task specialization is crucial for the ecological success of social insects. Carpenter ants allocate individuals of variable size to foraging, thus raising the question of whether they differ in their food preferences. We determined the sugar concentration at which an appetitive response occurs in small and large carpenter ants, and analyzed their distribution on natural and artificial nectar sources in a field assay. Under low starvation, larger ants responded more than smaller ants to higher sucrose concentrations. Coincidently, in the field assay, they were mainly present at sources with higher sucrose delivery. This kind of specialization may reflect the fact that larger ants have larger feeding apparatuses, which may confer a better capacity to deal with the higher viscosity of more concentrated nectars and allow collecting more food at nectaries with higher sugar flow rates. Size specialization may thus increase colony success in the exploitation of variable food sources. Fil: Josens, Roxana Beatriz. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Fisiología, Biología Molecular y Neurociencias. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Fisiología, Biología Molecular y Neurociencias; Argentina Fil: Lopez, M. Agustina. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Fisiología, Biología Molecular y Neurociencias. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Fisiología, Biología Molecular y Neurociencias; Argentina Fil: Jofré, Nélida. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Fisiología, Biología Molecular y Neurociencias. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Fisiología, Biología Molecular y Neurociencias; Argentina Fil: Giurfa, Martín. Centre National de la Recherche Scientifique; Francia

Specialized parasites are expected to express complex adaptations to their hosts. Manipulation of host behavior is such an adaptation. We studied the fungus Ophiocordyceps unilateralis, a locally specialized parasite of arboreal Camponotus leonardi ants. Ant-infecting Ophiocordyceps are known to make hosts bite onto vegetation before killing them. We show that this represents a fine-tuned fungal adaptation: an extended phenotype. Dead ants were found under leaves, attached by their mandibles, on the northern side of saplings similar to 25 cm above the soil, where temperature and humidity conditions were optimal for fungal growth. Experimental relocation confirmed that parasite fitness was lower outside this manipulative zone. Host resources were rapidly colonized and further secured by extensive internal structuring. Nutritional composition analysis indicated that such structuring allows the parasite to produce a large fruiting body for spore production. Our findings suggest that the osmotrophic lifestyle of fungi may have facilitated novel exploitation strategies.

Carpenter ants in the genus Camponotus (Hymenoptera: Formicidae) are considered some of the most serious pests to wood structures worldwide. There are over 900 species of carpenter ants in the world, 50 in the United States and Canada, and 12 in Utah. In nature, carpenter ants are most abundant in forests and can be easily found under loose bark of dead trees, stumps, or fallen logs.

The anatomical source of the trail pheromone in the black carpenter ant, Camponotus pennsylvanicus , was investigated by presenting workers with crude or synthetic hindgut extracts to test for attractancy and trail-following behavior. Chemical analysis was used in conjunction with behavioral bioassays to detect and identify volatiles from the rectal sac, poison, and Dufour's glands. The rectal material was also examined to determine levels of total nitrogen and identify metabolites in relation to other solid material present. Under laboratory conditions, foragers demonstrated a significant level of attraction to a combined Dufour's gland, poison gland, and rectal sac extract. No response was observed to synthetic compounds (formic acid and saturated hydrocarbons) from the poison or Dufour's gland. Two volatiles, n-undecane and n-tridecane, were identified from the Dufour's gland. Fatty acids and esters were found to be ubiquitous in the Dufour's and poison glands. Palmitic acid was identified in the poison gland. A compound described as a component of the trail pheromone in Camponotus atriceps (3,4-dihydro-3,5-dihydroxy-6-methyl-pyran-4-one) was identified in the rectum, but was not verified behaviorally as being part of the trail pheromone for C. pennsylvanicus . Trail following was not elicited from any of the rectal sac extracts. Dry weight analysis determined that the rectal material was only 14% solid material and total nitrogen levels were estimated at 19.2 ± 2 ug/mg of ant feces. Most of the components contributing to the total nitrogen excreted were left unidentified, but ammonia (2.7 ± 1.2 ug/mg), two tryptophan intermediates (kynurenic and xanthurenic acid) and one pteridine (biopterin), were identified. Master of Science

Aspects of the behavior, biology, and economic importance of carpenter ants were examined. The overall objectives of this study were to determine the economic importance of carpenter ants, and to extend the data currently available on two of the most common and economically important species in the U.S. A survey for the economic importance of carpenter ants indicated that carpenter ants are considered a serious pest by homeowners. The results show that 90% of the homeowners who requested control for carpenter ants during 1980, paid more than $25 for carpenter ant control. The presence of detectable damage was not the definitive factor in the decision to request control. Camponotus ferrugineus and C. pennsylvanicus are similar in their colony foundation and biology. C. ferrugineus required 54 days to produce the first brood and there were 18 workers, including one intermediate worker, in the first brood. Queens of C. pennsylvanicus required an average of 46 days to rear the first brood. Ad libitum feeding did not have a significant effect on colony founding in C. pennsylvanicus. Two queens reared their first brood under artificial light. Food preference studies of C. pennsylvanicus and C. ferrugineus indicated that these two species have similar food preferences. Although honey was preferred to most foods tested, it may not supply sufficient nutrients to ensure proper colony nutrition. C. pennsylvanicus has become well adapted to man-made structures. Some foraging ants are present year round. C. pennsylvanicus optimizes its foraging by exploiting indoor and outdoor foraging sites. The division of labor during nest construction may be based on subcaste. Major workers appear to be responsible for most nest-building in mature colonies. Master of Science