Fast Food Delivery: Is There a Way for Foraging Success in Leaf-Cutting Ants?

Walking long distances through a trail system is an intrinsic feature of the leaf-cutting ants. Workers travel hundred of meters to forage by using well-defined physical routes which are cleared of vegetation or obstacles. Despite the costs of construction and maintenance, cleared trails should promote more benefits than non-physical ones, especially related to the leaf supply for the colony. Here, the leaf delivery rate in constructed and non-constructed trails was compared by counting the foraging flow and travel time of workers. Also the length and width of trails were measured. It was found that leaf delivery rate was 67.47% higher for foragers who were walking along physical trails. The forager walking speed on physical trails had an increment of 86.10%. These significant increments might be related to the truly narrow corridor present inside physical trails that are leaf litter-free, and thereby chemically stronger and smoother than non-physical ones. The speed improvement could induce the construction of longer trails which guide the workers more efficiently to the foraging patch. Thus, physical trails have an important role in foraging efficiency as they allow workers go quickly and further to forage, since they limit a path and congregate more individuals, raising the leaf delivery rate. This study provides additional information about foraging trails of leaf-cutting ants

Comparison of the Ant Assemblages in Three Phytophysionomies: Rocky Field, Secondary Forest, and Riparian Forest-A Case Study in the State Park of Ibitipoca, Brazil

Ant assemblages are almost all related with the vegetation composition and so can provide us important information for conservation strategies, which are especially relevant to an environmentally protected area. We sampled the ant fauna in three different phytophysionomies in order to verify if the composition of ant species is different among the areas, especially because one of the areas is a Rocky Field and there is little information about the ant fauna in this habitat. A total of 8730 individuals were registered and an NMDS analysis showed that the ant assemblies are different at the three phytophysionomies (Rocky Field, Riparian Forest, and Secondary Forest). This study shows that the species that compose the ant assemblies in different phytophysionomies are a reflex of the environment, supporting the hypothesis that the vegetational composition results in different compositions in the ant assembly. Vegetal composition is determinant in the formation of the litter and consequently in the occurrence of ant species that depend on this layer of organic matter for nesting and foraging

Survival in a critical period: analysis of the reproductive event and the foundation period of colonies of Acromyrmex subterraneus

The nuptial flight and foundation period are the most critical periods in the life-cycle of ants, since factors such as predation, dissection, contamination and countless others can interfere with the dispersion and mating of the reproductive individuals, and in the digging and foraging of queens. The mortality rate is very high, so the decisions made should favor the survival and success of the individuals. Therefore, this study aims to investigate some aspects of the initial period of the life-cycle of Acromyrmex subterraneus in order to: i) clarify the advantages of the premature flight, as well as if its occurrence is smaller yet common to many colonies, or smaller due to the participation of less colonies; ii) evaluate the effect of the mass of queens on the survival and productivity of the incipient colonies; iii) evaluate the foraging cost to the queens in terms of energy and fitness during the colony foundation period. Genetic and morphological data revealed that the premature nuptial flight is an event restricted to a few colonies, and that the genetic factor must act in the development period of the individuals, accelerating this process and resulting in smaller individuals that reach maturity and depart for flight quicker. The reduction of competition for nesting sites and of potential conflict through greater kinship between the individuals could both be factors that favor the occurrence of this event. By evaluating the mass of young, founder queens, it was possible to verify that lighter queens have less chance of survival, and that the production of offspring is similar, regardless of presented initial mass. This indicates that intrinsic factors, such as the initial mass of queens at the moment of foundation, could also have significant influence on their mortality rate. Finally, it was revealed that the search for food does not affect the survival of the queens, and that the foraging cost during the foundation period is not directly linked to the lipid expenditure. Rather that at the time of caring for offspring, where queens that don’t need to leave the colony to search for food, they supposedly have more time to invest in raising and maintaining the colony, making it more populous more quickly.O voo nupcial e a fase de fundação são o período mais crítico no ciclo de vida das formigas, pois fatores como predação, dissecação, contaminação, e inúmeros outros podem interferir na dispersão e acasalamento dos indivíduos reprodutivos, na escavação e forrageamento das rainhas. A mortalidade durante este período é bastante alta e por isso as decisões tomadas devem favorecer a sobrevivência e o sucesso dos indivíduos. Sendo assim o presente estudo teve como objetivo investigar alguns aspectos do período inicial do ciclo de vida de Acromyrmex subterraneus a fim de i) esclarecer as vantagens do voo nupcial prematuro, bem como se sua ocorrência é menor porém comum a muitas colônias ou menor dada a participação de poucas colônias; ii) avaliar o efeito da massa das rainhas na sobrevivência e produtividade das colônias incipientes iii) por fim, avaliar o custo do forrageamento para rainhas em termos energéticos e em termos de fitness durante o período de fundação da colônia. Dados genéticos e morfológicos revelaram que o voo nupcial prematuro é um evento restrito a poucas colônias, e que o fator genético deve atuar no período de desenvolvimento dos indivíduos acelerando esse processo, resultando em indivíduos menores que atingem a maturidade mais rapidamente e logo então partem para o voo. A redução da competição por locais de nidificação e do potencial de conflitos através da maior relação de parentesco entre os indivíduos podem ser fatores que favoreçam a ocorrência desse evento. Avaliando a massa de jovens rainhas fundadoras foi possível constatar que rainhas mais leves têm menores chances de sobrevivência, e que a produção de prole é similar independente da massa apresentada, indicando que fatores intrínsecos, como a massa inicial das rainhas no momento da fundação, podem também ter significativa influência na sua taxa de mortalidade. Por fim, foi revelado que a busca por alimento por si não afeta a sobrevivência das rainhas, e que os custos do forrageamento durante o período de fundação não estão diretamente ligados ao gasto lipídico mas sim ao tempo de cuidado com a prole, onde rainhas que não precisam deixar a colônia para forragear supostamente têm mais tempo para investir na criação e manutenção da colônia tornando-a mais populosa rapidamente, aumentando as chances de sucesso

Investigação dos mecanismos comportamentais delineadores da composição de assembléias de formigas

In order to identify the mechanisms that form the ant assemblages in the rupestrian, this study was divided into three parts. In the first was investigated the species ability to find food resources and the behaviors influence of their permanence in the same resources. Baits were offered in a rupestrian area in Parque Estadual do Ibitipoca, MG. Were made 60 records, on a 10 baits/quadrant, totaling 40 hours of recording. Of the nine most common species Pheidole obscurithorax, Pheidole radoszkowskii, Pheidole sp.6 and Crematogaster sericea showed highest values for discovery ability and tended to stay longer in the baits. Camponotus crassus, Camponotus renggeri, Ectatomma edentatum, Camponotus genatus, Pachycondyla striata were species with lower permanence rates, may be considered as submissive species due to lower competitive ability. The behavior also influenced the permanence and ranged between agonistic coexistence depending on the species and the context in which the interaction occurred. The two species with greater ability to find resources – P. obscurithorax and C. sericea – were selected for the second part of the study. In order to evaluate competitive mechanisms in places far and near to their nests, has been investigated the influence of distance from the resource until the nest in the aggression and abundance, and the hierarchical status during the foraging. We established an observation plot for each nest, composed by eight baits: four located 1.5m away from the nests and four 0.5m. The baits were observed one at a time, totaling 256 records/species. The behaviors recorded were attack and advance. For both species, the distance of the food to the nest had no effect on aggression (Z= 1,44; p=0,07 C. sericea; Z= 1,44; p=0,07 P. obscurithorax); the abundance of P obscurithorax was higher in the baits near its nest (F = 7.30, p <0.01), while for C. sericea did not differ between near and far baits (F=2,19; p=0,14). In spite of being strong competitors, C. sericea and P. obscurithorax foraged according to their hierarchical status, being the first territorialist and the second aggressive not territorialist. In the third part, we investigated the behavioral patterns of aggressiveness among C. sericea and P. obscurithorax colonies located near (2.40 m) and far (15.60 m) from each other based on the Dear Enemy Hypothesis. We captured 50 individuals/colony to perform dyadic encounters. Were conducted 10 meetings/treatment: control, near interspecific and far interspecific. The behaviors observed were: inspection, antenna touch, self-grooming, avoidance, forward, open jaw, bite, bend the gaster and fight. For each action was assigned a value, used to calculate the aggression rate. Was found more aggressiveness of C. sericea when confronted with P. obscurithorax from the nearby colony (t=-4,935; p<0,001). In contrast, there were no significant difference in x aggressiveness displayed between workers of P. obscurithorax and C. sericea from the far colony (t=0,617; p=0,995). The aggressiveness of C. sericea directed to their neighbors certifies that, in addition to the recognition between different species, P. obscurithorax also can be considered a strong competitor, then Dear Enemy Hypothesis cannot be applicable to these species.Buscando identificar os mecanismos formadores das assembleias de formigas em campo rupestre, este estudo foi dividido em três partes. A primeira investigou a habilidade das espécies em descobrir recursos alimentares e a influência dos comportamentos na sua permanência nos mesmos. Iscas atrativas foram oferecidas em uma área de campo rupestre no Parque Estadual do Ibitipoca, MG. Foram realizados 60 registros, referentes a 10 iscas/quadrante, totalizando 40 horas de filmagem. Das nove espécies mais freqüentes Pheidole obscurithorax, Pheidole radoszkowskii, Pheidole sp.6 e Crematogaster sericea foram as que apresentaram maiores valores para habilidade de descoberta e tenderam a permanecer por mais tempo nas iscas; Camponotus crassus, Camponotus renggeri, Ectatomma edentatum, Camponotus genatus, Pachycondyla striata foram espécies com menores taxas de permanência, podendo ser consideradas como submissas devido à menor habilidade competitiva. Os comportamentos também influenciaram na permanência e variaram entre agonísticos e de coexistência em função da espécie e do contexto no qual ocorreu a interação. As duas espécies com maior habilidade em descobrir os recursos - C. sericea e P. obscurithorax - foram selecionadas para a segunda parte do estudo. Objetivando avaliar mecanismos competitivos em locais distantes e próximos aos seus ninhos, foi averiguada a influência da distância do recurso ao ninho na agressividade e abundância, bem como o status hierárquico durante o forrageamento. Foi estabelecido um plot de observação para cada ninho composto por oito iscas: quatro localizadas a 1,5m de distância dos ninhos e quatro a 0,5m. As iscas foram observadas uma por vez, totalizando 256 registros/espécie. Os comportamentos registrados foram ataque e avançar. Para ambas as espécies a distância do alimento ao ninho não influenciou na agressividade (Z= 1,44; p=0,07 C. sericea; Z= 1,44; p=0,07 P. obscurithorax); a abundância de P. obscurithorax foi maior nas iscas próximas ao seu ninho (F= 7,30; p<0,01), enquanto que para C. sericea não diferiu entre iscas próximas e distantes (F=2,19; p=0,14). Apesar de fortes competidoras, C. sericea e P. obscurithorax forragearam de acordo com seus status hierárquico, sendo a primeira territorialista e a segunda agressiva não territorialista. Na terceira parte foram investigados os padrões comportamentais de agressividade entre colônias de C. sericea e P. obscurithorax localizadas próximas (2,40m) e distantes (15,60m) entre si baseado na Hipótese do Inimigo Querido. Foram capturados 50 indivíduos/colônia para execução de encontros diádicos. Foram realizados 10 encontros/tratamento: controle, interespecífico próximo e interespecífico distante. Os comportamentos observados foram: inspeção, toque de antena, auto-grooming, viii evitar, avançar, abertura de mandíbula, morder, curvar o gáster e luta. Para cada ato foi atribuído um valor, utilizado no cálculo do índice de agressão. Verificou-se maior agressividade de C. sericea quando confrontadas com P. obscurithorax provenientes da colônia próxima (t=-4,935; p<0,001). Em contraste, não houve diferença significativa na agressividade exibida entre operárias de P. obscurithorax e C. sericea provenientes da colônia distante (t=0,617; p=0,995). A agressividade de C. sericea direcionada aos seus vizinhos atesta que, além de haver o reconhecimento entre diferentes espécies, P. obscurithorax pode ser considerada uma forte competidora, não sendo aplicável a hipótese do inimigo querido a estas espécies.FAPEMIG - Fundação de Amparo à Pesquisa do Estado de Minas Gerai

Figure 2 in Necrophagous or predators? The role of Pheidole radoszkowskii Mayr (Hymenoptera: Formicidae) on Rattus norvegicus (Berkenhout) carcasses (Rodentia: Muridae)

Figure 2. Average number of Pheidole radoszkowskii that exhibited necrophagous feeding behaviour – NFB – (fed on exudates and on pieces of flesh from the carcass) and predatory feeding behaviour – PFB – (predated on fly larvae).Published as part of Sales, Tatiane Archanjo de, Daemon, Erik & Lopes, Juliane Floriano Santos, 2015, Necrophagous or predators? The role of Pheidole radoszkowskii Mayr (Hymenoptera: Formicidae) on Rattus norvegicus (Berkenhout) carcasses (Rodentia: Muridae), pp. 971-974 in Journal of Natural History 50 on page 973, DOI: 10.1080/00222933.2015.1091100, http://zenodo.org/record/399013

A convenient trip: an analysis of the impact of Hitchhiker ants on forager transport rates

During foraging, leaf-cutting ant workers of different size classes perform various tasks along foraging trails. Commonly, small workers called hitchhikers climb on leaf fragments imposing an extra transport cost, so their presence is thought to reduce the individual foraging performance. There are four main hypotheses which may explain the occurrence of hitchhikers and a different behavioral act related to their role can be predicted for each. Hitchhiker behavior was observed considering these hypotheses and the effect of the hitchhikers on the walking speed and transport rate of foragers was evaluated. The behavioral registers were obtained from 1371 hitchhikers on foraging trails of Acromyrmex subterraneus subterraneus nests in the field. To verify the influence of hitchhikers on walking speed and transport rate, 239 foragers with hitchhikers and 250 foragers transporting only leaf fragments were analyzed. The walking speed, burden and transport rate of each forager were calculated. Data indicated not only that hitchhikers are vigilant but that they remain motionless on the leaf fragment probably in order to reduce the impact of their presence for the loaded forager. The impact of their presence is verified through walking speed reduction but as they ride preferentially on larger workers who transport larger leaf fragments, there are no losses in the individual transport rate. The transporter selection made by the hitchhiker ensures at the same time enhanced protection against phorid parasitoids and the maintenance of the leaf transport rate

Influencia de la elaboración de pronósticos de demanda en los costos de la empresa Darbha SAC, Cajamarca - 2017

RESUMEN La Empresa DARBHA S.A.C se dedica a brindar servicios de educación universitaria a nivel de postgrado, investigación, capacitación de personas del sector público y privado, organización de eventos educativos y culturales de forma presencial, semipresencial y a distancia. Esta empresa no contaba con un estudio de pronóstico de demanda de los cursos y/o diplomados que ofrece, por lo se registra pérdidas económicas en algunos diplomados al no conseguir la demanda esperada. Para ello se realizó una investigación donde se determinó la influencia de pronósticos de la demanda en los costos de la empresa DARBHA SAC, teniendo un diseño de investigación transversal correlacional. Se identificó el comportamiento de los costos en el historial de la empresa donde se pudo observar que hay una tienen una tendencia periódica cada tres meses con respecto a la demanda de matriculados, se determinó la metodología apropiada para pronosticar la demanda de la empresa, se pronosticó la demanda para ocho periodos siguientes mediante el método de serie de tiempos usando el Minitab, con un punto de equilibrio de veinte matriculados. Como resultado para poder verificar la viabilidad del proyecto se realizó la valoración económica obteniendo un WACC del 8.06%, el cual nos indica que la propuesta es viable. Con lo antes mencionado se puede concluir que el pronóstico de demanda influye considerablemente en los costos de la empresa, además de tener una relación significativa, con un R = 0.9 se logró determinar que la elaboración de pronóstico de la demanda y los costos de la empresa se relacionan significativamente. PALABRAS CLAVE: Pronósticos, influencia, costos, demanda, serie de tiempos.ABSTRACT The Company DARBHA S.A.C is dedicated to providing university education services at postgraduate level, research, training of people from the public and private sector, organization of educational and cultural events in person, in person and at a distance. This company did not have a demand forecast study of the courses and / or diplomas offered, so there are economic losses in some graduates by not achieving the expected demand. For this, a research was carried out where the influence of demand forecasts on the costs of DARBHA SAC was determined, having a correlational cross-sectional research design. It was identified the behavior of the costs in the history of the company where it was possible to observe that there is a periodic tendency every three months with respect to the demand of enrolled ones, it was determined the appropriate methodology to predict the demand of the company, it was predicted the demand for eight following periods using the time series method using the Minitab, with a break-even point of twenty enrolled. As a result, to verify the feasibility of the project, the economic valuation was obtained, obtaining a WACC of 8.06%, which indicates that the proposal is viable. With the aforementioned, it can be concluded that the forecast of demand influences considerably the costs of the company, in addition to having a significant relation, with R2 = 0.9 it was possible to determine that the elaboration of forecast of the demand and the costs of the company are significantly relat

Necrophagous or predators? The role of Pheidole radoszkowskii

Figure 2. Average number of Pheidole radoszkowskii that exhibited necrophagous feeding behaviour – NFB – (fed on exudates and on pieces of flesh from the carcass) and predatory feeding behaviour – PFB – (predated on fly larvae).Published as part of Sales, Tatiane Archanjo de, Daemon, Erik & Lopes, Juliane Floriano Santos, 2015, Necrophagous or predators? The role of Pheidole radoszkowskii Mayr (Hymenoptera: Formicidae) on Rattus norvegicus (Berkenhout) carcasses (Rodentia: Muridae), pp. 971-974 in Journal of Natural History 50 on page 973, DOI: 10.1080/00222933.2015.1091100, http://zenodo.org/record/399013