Control químico de Pogonomyrmex barbatus con atrayentes de maíz, en Irapuato, Guanajuato, México

Introducción. Las hormigas granívoras tienen impacto económico y ecológico al ser consideradas plagas agrícolas que transportan semillas y defolian plantas cultivadas. Objetivo. El objetivo de este trabajo fue evaluar la efectividad de los insecticidas Imidacloprid y Novalurón en mezcla, con tres atrayentes a base de harina de maíz para el control de Pogonomyrmex barbatus, en pruebas de campo en Irapuato, Guanajuato, México. Materiales y métodos. Esta investigación se realizó de agosto a noviembre del 2014, se consideraron seis tratamientos, los tres primeros consistieron de la mezcla de Imidacloprid con harina de maíz (en pellet molido fino, en pellet molido y sin pelletizar), el cuarto de Novalurón combinado con harina de maíz en pellet molido, y los últimos dos constaron solamente de harina de maíz (en pellet molido fino y sin pelletizar), además de un testigo absoluto. Se realizaron conteos de individuos por minuto antes (lectura a 0 h) y después de la aplicación de los tratamientos (lecturas a 1, 24, 72, 144 y 240 h) en el exterior de tres hormigueros seleccionados previamente para tal fin. Se realizó el análisis de varianza del diseño completamente al azar con arreglo en franjas sub-subdivididas con tres repeticiones, y tres factores que fueron los siguientes: seis tratamientos y el testigo absoluto, seis lecturas a través del tiempo incluyendo el conteo previo a la aplicación de los tratamientos y los tres hormigueros. Resultados. Se presentaron diferencias estadísticas altamente significativas para los factores: tratamientos y lecturas, así como para la interacción entre ambos. Conclusión. Los tratamientos con insecticida mostraron su máximo control a las 72 h de su aplicación, los mejores fueron el Imidacloprid combinado con harina de maíz en dos presentaciones (en pellet molido y sin pelletizar), con mayor eficacia a partir de las 24 h de su aplicación.

Metastriate Ixodid Life Stages Protected from Predatory Ants in Texas

Multiple predatory ant species, including the red imported fire ant, Solenopsis invicta (Buren) (Hymenoptera: Formicidae), have been reported to attack ixodids (Ixodida: Ixodidae), but evidence has largely been circumstantial. When living lone star tick, Amblyomma americanum (L.) (Acarina: Ixodidae), eggs, and unfed and blood-engorged larvae, nymphs, and adults were deployed on bait transects with hot dog slices and dead house flies, Musca domestica L., in West, Central, and South Texas. The various ixodid life stages were not attacked while ants were strongly recruited to the hot dog and M. domestica baits. Similarly, when the same ixodid life stages and other baits were placed adjacent to colonies of two ant species (red harvester ant, Pogonomyrmex barbatus (Smith) and the red imported fire ant, Solenopsis invicta Buren) the ixodids were not preyed upon while hot dog slices and dead M. domestica were immediately attacked. Some ant species dragged blood-engorged adult ixodids and eggs away from the colony entrance, where they were originally placed, and discarded them. Evidence and mechanisms for allomone-based ant deterrence in the genera Amblyomma, Dermacentor, and Rhipicephalus (metastriate ixodids) are discussed. Protection of ixodids from predatory ants helps to explain why metastriate ixodids remain problematic worldwide despite the presence of predaceous ants.

The Ecology of Collective Behavior in Ants

Nest choice in Temnothorax spp.; task allocation and the regulation of activity in Pheidole dentata, Pogonomyrmex barbatus, and Atta spp.; and trail networks in Monomorium pharaonis and Cephalotes goniodontus all provide examples of correspondences between the dynamics of the environment and the dynamics of collective behavior. Some important aspects of the dynamics of the environment include stability, the threat of rupture or disturbance, the ratio of inflow and outflow of resources or energy, and the distribution of resources. These correspond to the dynamics of collective behavior, including the extent of amplification, how feedback instigates and inhibits activity, and the extent to which the interactions that provide the information to regulate behavior are local or spatially centralized.

A New Protocol Using Artificial Seeds to Evaluate Dietary Preferences of Harvester Ants in Semi-arid Environments

The preferences of seed intake by harvester ants (Pogonomyrmex spp.) have been debated for a long time, mainly due the lack of repeatable methods to draw clear conclusions. However, several characteristics of the food resource are well recognized as the drivers of such selective predation. For instance, resource quality (i.e., availability of carbohydrates, lipids, and proteins) is one factor that could explain the observed foraging patterns of Pogonomyrmex species. In this sense, experimental approaches using artificial resources (e.g., synthetic seeds/diaspores) have provided an useful and alternative tool to study ant’s food foraging behavior. Therefore, it is expected that the use of artificial seeds also could offer a versatile way to assess the influence of resource quality exert on the resource selection by harvester ants. On the other hand, empirical experiments involving harvester ants and artificial seeds are still rare in the literature and it is not known if such methodology is efficient with different Pogonomyrmex species. In this study carried out in a Neotropical arid environment of central Mexico, we tested a simple but fundamental question: Do harvester ants (Pogonomyrmex barbatus) predate artificial seeds with manipulated nutrient content (lipids and proteins) in the field? We found that the proportion of native seeds removed was lower than the proportion of artificial seeds removed. However, we found no difference between the removal of artificial seeds containing only lipids and the seeds containing lipids + proteins. These findings indicate that the artificial seeds synthesized by us could be an effective method to test different ecological hypothesis involving harvester ants. Moreover, our empirical experiment offers a benchmark to study the influence of resource quality on the food foraging behavior of harvester ants in Neotropical arid environments.

Hormigas (Hymenoptera: Formicidae) de Aguascalientes

Se elaboró una lista de especies de hormigas con base en los ejemplares depositados en las colecciones entomológicas de la Universidad Autónoma de Aguascalientes y de la Universidad de Guadalajara, así como con información obtenida en publicaciones especializadas sobre la familia Formicidae para el estado de Aguascalientes. Se conocen 32 especies de hormigas para el mismo: Atta mexicana, Pogonomyrmex barbatus, P. rugosus y Myrmecocystus melliger son de las que se tiene mayor número de ejemplares. El municipio de Aguascalientes es el que cuenta con el mayor número de especies registradas, 19; San José de Gracia con 11 y Calvillo con 10. En los municipios de Cosío, El Llano, Rincón de Romos y Tepezalá no se tienen especies de hormigas registradas. Se requiere mayor esfuerzo enfocado al estudio de hormigas en Aguascalientes.

Experimental modulation of external microbiome affects nestmate recognition in harvester ants (Pogonomyrmex barbatus)

Social insects use odors as cues for a variety of behavioral responses, including nestmate recognition. Past research on nestmate recognition indicates cuticular hydrocarbons are important nestmate discriminators for social insects, but other factors are likely to contribute to colony-specific odors. Here we experimentally tested whether external microbes contribute to nestmate recognition in red harvester ants (Pogonomyrmex barbatus). We changed the external microbiome of ants through topical application of either antibiotics or microbial cultures. We then observed behavior of nestmates when treated ants were returned to the nest. Ants whose external microbiome was augmented with microbial cultures were much more likely to be rejected than controls, but ants treated with antibiotics were not. This result is consistent with the possibility that external microbes are used for nestmate recognition.