The discrepancy between fire ant recruitment to and performance on rodent carrion

Ants have not been considered important in the process of vertebrate carrion decomposition, but a recent literature review reported over 150 carrion-visiting ant species. Though many ant species have been observed to remove carrion tissue and consume carrion-exuded liquids, the significance of ant recruitment to vertebrate carrion is poorly understood. We conducted a combination of field and laboratory experiments to quantify red imported fire ant recruitment to rodent carrion and determine whether consuming rodent carrion is beneficial to ant colony performance. In the field, 100% of rat carcasses were rapidly colonized by fire ants at high abundances. In our laboratory experiment, the performance of mice-fed fire ant colonies was poor when compared to colonies that were fed mice and insects or insects only. Our results suggest that there is a discrepancy between high levels of fire ant recruitment to vertebrate carrion and the poor colony performance when fed carrion. We hypothesize that fire ants are attracted to vertebrate carrion not because it is a high-quality food, but rather because it hosts large numbers of other invertebrates that can serve as prey for fire ants, potentially showcasing an interesting case of tritrophic interaction in carrion ecology.

Females restrict the position of domatia and suffer more herbivory than hermaphrodites in Myriocarpa longipes, a neotropical facultative myrmecophyte

Domatia are hollow structures in plants occupied by ant colonies, in turn ants provide protection against herbivores. In plants, competition for resources has driven sex-related changes in the patterns of resource allocation to life-history traits and defence traits. The resource-competition hypothesis (RCH) proposes that female plants due to their higher investment in reproduction will allocate fewer resources to defence production, showing greater herbivore damage than other sexual forms. We hypothesise the existence of sex-related differences in defensive traits of domatia-bearing plants, being female plants less defended due to differences in domatia traits, such as size, number of domatia and their position, exhibiting more herbivore damage than hermaphrodite plants of Myriocarpa longipes, a facultative neotropical myrmecophyte. We found eight species of ants inhabiting domatia; some species co-inhabited the same plant, even the same branch. Our results are consistent with the predictions of RCH, as female plants had ant-inhabited domatia restricted to the middle position of their branches and exhibited greater herbivore damage in leaves than hermaphrodites. However, we did not find differences in domatia size and leaf area between sexual forms. Our study provides evidence for intersexual differences in domatia position and herbivory in a facultative ant–plant mutualism in M. longipes. We highlight the importance of considering the plant sex in ant–plant interactions. Differences in resource allocation related to sexual reproduction could influence the outcome of ant–plant interactions.

Determination of the Shortest Route on the Distribution System using Ant Colony Optimization (ACO) Algorithm (Case Study: Alfamidi Palu Branch – PT. Midi Utama Indonesia)

The distribution system of goods is one of the most important parts for every company. The company certainly has many route options to visit, and this is expected to be conducted efficiently in terms of time. In the distribution of goods by Alfamidi company in Palu City which has 51 outlets include into the category of Traveling Salesman Problem (TSP) because of many route options that can be visited. The problem can be solved by employing the Ant Colony Optimization (ACO) method which is one of the algorithms Ant Colony System (ACS). The ACS acquires principles based on the behavior of ant colonies and applies three characteristics to determine the shortest route namely status transition rules, local pheromone renewal and global pheromones. The result showed that the shortest route of the distribution of goods based on the calculation of selected iterations was ant 1 with the shortest total distance obtained 86.98 km.

A fungus infected environment does not alter the behaviour of foraging ants

Eusocial insects are exposed to a wide range of pathogens while foraging outside their nest. We know that opportunistic scavenging ants are able to assess the sanitary state of food and to discriminate a prey which died from infection by the entomopathogenic fungus Metarhizium brunneum. Here, we investigate whether a contamination of the environment can also influence the behaviour of foragers, both at the individual and collective level. In a Y-maze, Myrmica rubra ants had the choice to forage on two prey patches, one of which containing sporulating items. Unexpectedly, the nearby presence of sporulating bodies did not deter foragers nor prevent them from retrieving palatable prey. Ant colonies exploited both prey patches equally, without further mortality resulting from foraging on the contaminated area. Thus, a contamination of the environment did not prompt an active avoidance by foragers of which the activity depended primarily on the food characteristics. Generalist entomopathogenic fungi such as M. brunneum in the area around the nest appear more to be of a nuisance to ant foragers than a major selective force driving them to adopt avoidance strategies. We discuss the cost–benefit balance derived from the fine-tuning of strategies of pathogen avoidance in ants.

Validation of the method for evaluating the efficacy of food baits against pharaoh ant colonies

The validation of the method for testing the effectiveness of food baits against colonies of the Pharaoh ant using experiments with commercially produced and laboratory-prepared sugar baits containing insecticides from different chemical groups was carried out. We studied baits based on boron compounds (boric acid and sodium tetraborate), neonicotinoids (thiamethoxam, imidacloprid, and acetamiprid), oxadiazines (indoxacarb), phenylpyrazoles (fipronil), carbamates (methomyl), pyrroles (chlorfenapyr) amidinohydrazones (hydramethylnon), avermectins (abamectin), and insect growth regulators (pyriproxyfen). The proposed algorithm for conducting experiments covers the whole variety of active ingredients of insecticides used in baits. The verification of several dozen products intended for the elimination of colonies of the Pharaoh ant has shown that most of the products are suitable for the requirements for efficacy indices. Keywords: Pharaoh ant, insecticidal baits.

Protokoll der Jahresversammlung der Schweizerischen Entomologischen Gesellschaft vom 5. März und 21. Juni 2021 via Videokonferenz

Aufgrund der anhaltenden Corona-Pandemie musste die Jahresversammlung leider auf einen Tag reduziert werden und ohne physische Präsenz stattfinden. Sie wurde daher per Videokonferenz abgehalten. Der Präsident Oliver Martin hatte dafür ein Meeting via Zoom organisiert, das reibungslos ablief. Trotz der erschwerten Umstände konnte ein interessantes Vortragsprogramm für die Jahresversammlung zusammengestellt werden. Den Themenschwerpunkt bildete die experimentelle Forschung mit Hymenopteren, jedoch aus ganz unterschiedlichen Fachgebieten. Das Programm startete mit dem Hauptvortrag von Yuko Ulrich, Professorin an der ETH Zürich, zum Thema Sozialverhalten und Krankheitsdynamik bei Ameisen. Darin gab sie einen Einblick, wie im Labor soziale Interaktionen und die Mechanismen der Entstehung von Arbeitsteilung untersucht werden. Als Modellorganismus diente die räuberische Ameisenart Ooceraea biroi, die keine Königinnen ausbildet. Stattdessen vermehren sich alle Individuen parthenogenetisch, was den Faktor der genetischen Varianz in Experimenten deutlich reduziert. Mittels Kameras über mehreren Dutzend Ameisenkolonien und Farbcodes auf den Tieren konnte das Verhalten und der Aufenthaltsort (im Nest oder ausserhalb des Nests) jedes Individuums analysiert werden. Dann wurde der Einfluss der Koloniegrösse, sowie der Mischung von Genotypen und Körpergrössen innerhalb einer Ameisengruppe auf das Verhalten der Tiere untersucht. Abschliessend berichtete Frau Ulrich über die neueste Forschung mit experimentell infizierten Ameisen. Von Pilzsporen befallene Tiere werden intensiver von Artgenossen betreut, wodurch ihre Überlebensrate stark steigt. In zukünftigen Studien sollen die genannten Untersuchungen über mehrere Generationen von Ameisen hinweg ausgedehnt werden. ● Social behaviour and disease dynamics in clonal ant colonies. Yuko Ulrich, ETH Zürich ● Defensive symbionts protect aphids from parasitoid wasps depending on stable genotype-by-genotype interactions. Elena Gimmi, Eawag / ETH Zürich ● Megachile sculpturalis Smith, 1853 (Hymenoptera: Megachilidae), an Asian wild bee populates Europe. Julia Lanner, Universität für Bodenkultur Wien / Universität Bern ● Homemade or take away: Where do the cuticular hydrocarbons of parasitoid wasps come from? Corinne Hertäg, ETH Zürich ● Entwicklungsbiologische Ursachen sexueller Merkmale bei Mistkäfern: Wie macht man lange Beine? Patrick Rohner, Indiana University Der ETH Zürich sei für das Zurverfügungstellen des Videokonferenzraums herzlich gedankt.

Temporal Variation in Toxic Bait, Carbohydrate and Protein Preference and Toxic Bait Efficacy in Argentine (Linepithema Humile) and Darwin’s Ants (Doleromyrma Darwiniana)

<p>By determining if there is any temporal variation in toxic bait, carbohydrate and protein preference in Argentine and Darwin’s ants, we can provide better control options because we can identify with more accuracy when ants will be foraging for one food type over another. Improving our understanding is also fundamental as we can improve future bait formulations, bait application and timing, and increase levels of bait uptake. I have two aims in this thesis. First, I investigated toxic bait, carbohydrate and protein preferences for Argentine ants (Linepithema humile) and Darwin's ant (Doleromyrma darwiniana). The second aim in my thesis was to examine the efficacy of toxic baits in laboratory colonies of Argentine ants. Food preferences varied between species and within species considerably throughout the year, although Darwin's ant consistently favoured foods higher in carbohydrates. Argentine ants showed a significant preference for protein over carbohydrates during December and January. Despite differences in carbohydrate and protein preferences the preference for individual toxic baits showed little temporal variation. The toxic bait efficacy experiment revealed that Xstinguish™ and Exterm-an-Ant® baits produced the highest mortality rate. Other commercially available toxic baits had little effect on workers or queens. The efficacy of the toxic baits was influenced by the starvation level of the ant colonies, and only the colonies that were starved for 48 hours experienced a 100% mortality rate. Due to these results, I recommend that bait application with Xstinguish™ and Exterm-an-Ant® in late winter-spring would be optimal as this time frame is when ants are likely to be starved, and when foraging activity is increasing, thus maximising the chances of bait uptake. A second round of baiting treatment with both baits (Xstinguish™ and Exterm-an-Ant®) in summer when Argentine ants have been shown to undergo a second wave of reproduction could also be beneficial.</p>