Hormigas arbóreas del Parque Nacional Natural Gorgona (Pacífico de Colombia) / Arboreal ants of the Gorgona National Natural Park (Pacific of Colombia)

Arboreal ants of Gorgona National Park (Pacific of Colombia). Despite the strong microclimatic fluctuations, scarcity of nesting sites and unpredictable prey availability in open environments, ants are the dominant invertebrates in the tropical forest canopy. This study focused on the arboreal ants in Gorgona National Park, Colombia, a rainforest ecosystem (27ºC, 6 000mm average annual rainfall). In November 2007, 16 trees were sampled by fogging them with a biodegradable pyrethroid insecticide in four levels between 1 and 15 m above the understory vegetation. We found 53 species of Formicidae (24 genera and six subfamilies): two subfamilies had the most species: Formicinae (20 species) and Myrmicinae (17). The most abundant were arboreal species of Azteca, Dolichoderus (D. bispinosus and D. lutosus), Camponotus (C. atriceps, C. claviscapus, C. championi, C. excisus) and Crematogaster (C. brasiliensis, C. carinata, C. curvispinosa). Some species that are common at ground level (Wasmannia auropunctata and Camponotus sericeiventris) were collected up to a height of 15 m. We remark the capture of Nesomyrmex pittieri, Crematogaster stolli, Cephalotes basalis, Anochetus bispinosus and Stigmatomma mystriops, species rarely found using conventional methods. Rev. Biol. Trop. 62 (Suppl. 1): 277-287. Epub 2014 February 01.

Este trabajo se enfocó en el conocimiento de la mirmecofauna arbórea de Gorgona, ecosistema insular de la zona de vida de bosque lluvioso tropical (27ºC, 6 000mm de precipitación promedio anual). En noviembre de 2007 se muestrearon 16 árboles mediante la técnica de nebulización usando un insecticida piretroide biodegradable, aplicado en dirección al dosel, desde cuatro alturas diferentes, entre 1 y 15m por encima de la vegetación del sotobosque. Se encontraron 53 especies de Formicidae pertenecientes a 24 géneros y seis subfamilias, sobresaliendo por su riqueza las Formicinae (20 especies) y Myrmicinae (17). Por su abundancia, se destacaron especies arbóreas de los géneros Azteca, Dolichoderus (D. bispinosus y D. lutosus), Camponotus (C. atriceps, C. claviscapus, C. championi, C. excisus) y Crematogaster (C. brasiliensis, C. carinata, C. curvispinosa). Algunas especies que son muy comunes a nivel del suelo (Wasmannia auropunctata y Camponotus sericeiventris), fueron colectadas a más de 15m de altura. Se resalta la captura de Nesomyrmex pittieri, Crematogaster stolli, Cephalotes basalis, Anochetus bispinosus y Stigmatomma mystriops que usualmente no se detectan en muestreos comunes.

Especies de hormigas del suelo en el Parque Nacional Natural Gorgona, Pacífico Colombiano / Soil ant species in Gorgona Island, Colombian Pacific

Soil ant species in Gorgona Island, Colombian Pacific. Gorgona is one of the two insular areas of the Colombian tropical rain forest at the Pacific and is amongst the most diverse biogeographic regions of the world, the Choco. This study compiles information on ant species from published (1991) and unpublished (2006) studies and provides new records for ant species collected in 2010. Ants were sampled and information was obtained from 15 sites in Gorgona island (13.82km²), including the Gorgonilla atoll (0.49km²). Collecting methods included pitfall traps, tuna baits, mini-Winkler extraction of leaf litter, Malaise traps, entomological net and direct search. The soil and understory ant inventory resulted in 107 ant species and morphospecies, 46 genera in 12 subfamilies. Myrmicinae held the highest species richness (37 species), followed by Ponerinae (27) and Formicinae (12). The richest genera were Pachycondyla (15 species), Camponotus (nine) and Pheidole (eight), while 30 genera were represented by a single species. Twelve species were very common (both in distribution and time): Azteca sp., Atta cephalotes, Camponotus sericeiventris, Eciton vagans, Ectatomma goninion, Gnamptogenys annulata, Odontomachus bauri, Pachycondyla bugabensis, P. harpax, P. verenae, Paraponera clavata and Wasmannia auropunctata. Direct search was the most efficient method to collect diferent species and was responsible for 52% of the total species found. Compared to other Neotropical islands, Gorgona holds a suprisingly high number of ant species, none of them invasive. The invasive Monomorium floricola, which was collected 20 years ago, was not found in 2010. These evidences suggest that ecological mechanisms and natural recovery processes in the ecosystem have generated microhabitats allowing their coexistence. Rev. Biol. Trop. 62 (Suppl. 1): 265-276. Epub 2014 February 01.

Este trabajo compila registros publicados (1991) y no publicados (2006) sobre las especies de hormigas del PNN Gorgona y aporta nuevos registros de especies recolectadas en 2010. Se recopiló información de 15 diferentes sitios de isla Gorgona (13.82km²), incluyendo la pequeña isla de Gorgonilla (0.4899km²). Los métodos de recolecta incluyeron trampas de caída, cebos de atún, sacos Winkler, trampas Malaise, red entomológica y captura directa. El inventario de hormigas de suelo y sotobosque resultó en 107 especies y morfoespecies, 46 géneros y 12 subfamilias. Myrmicinae reunió la mayor riqueza (37 especies) seguida de Ponerinae (27) y Formicinae (12). Los géneros más ricos fueron Pachycondyla (15 especies), Camponotus (nueve) y Pheidole (ocho), mientras que 30 géneros solo presentaron una especie. Doce especies fueron muy comunes: Azteca sp., Atta cephalotes, Camponotus sericeiventris, Eciton vagans, Ectatomma goninion, Gnamptogenys annulata, Odontomachus bauri, Pachycondyla bugabensis, P. harpax, P. verenae, Paraponera clavata y Wasmannia auropunctata. En comparación con otras islas neotropicales, Gorgona tiene un número sorprendentemente elevado de especies de hormigas, ninguna de ellas invasivas. Por tanto, estos resultados sugieren que, mecanismos ecológicos y procesos de recuperación natural en el ecosistema han generado disponibilidad de microhábitats permitiendo la coexistencia una gran riqueza de especies.

Morphological and morphometric studies of the antennal sensilla from two populations of Atta robusta (Borgmeier 1939) (Hymenoptera: Formicidae) / Estudo morfológico e morfométrico das sensilas antenais de Atta robusta (Borgmeier 1939) (Hymenoptera: Formicidae)

The ant Atta robusta is endemic to the “restinga” ecosystems where it has an important role in the dynamics of seed dispersal. Despite its importance, A. robusta is considered a threatened species. In this study we analyzed the antennal sensory organs of two different populations of A. robusta (from the cities of São Mateus and Maricá in in Espírito Santo and Rio de Janeiro States, respectively) using a scanning electron microscope (SEM). SEM revealed different types of sensilla in the A. robusta antennae, i.e., curved and straight trichoid, basiconic, ampullacea and coeloconic, which were highly abundant found in the distal flagellomeres (F) compared with other antenna regions. There were differences in samples collected from two locations in terms of the sensilla number and length. The average numbers of straight and curved trichoid sensillae numbers were different in F9 and F8, respectively, while the average length of the curved trichoid sensilla was only different in F9. These variations in sensory organs between two populations of A. robusta may indicate an adaptation of this species to different environmental conditions. The number of straight trichoid sensilla was only significantly different in F9.

Atta robusta é uma espécie de formiga endêmica, com papel importante na dinâmica dos ecossistemas de restinga. Apesar de sua importância como dispersora de sementes nesse tipo de ecossistema, essa espécie encontra-se ameçada de extinção. O presente trabalho lançou mão da microscopia eletrônica de varredura (MEV) para descrever as sensilas antenais de A. robusta e investigar diferenças entre sensilas antenais dessa espécie em indivíduos coletados em localidades diferentes, nos municípios de São Mateus (Estado do Espírito Santo) e Maricá (Estado do Rio de Janeiro). Diferentes tipos de sensilas como tricoideas retas e curvadas, basicônicas, ampuláceas e celocônicas foram encontradas nas antenas, sendo que todas são mais numerosas no flagelomero nove (F9) ou mais distal. Houve diferença em número e em comprimento das sensilas tricoideas retas e curvatas em F8 e F9 entre os indivíduos das duas localidades. Os números médios das sensilas tricoides retas e curvadas foram diferentes para os F9 e F8, respectivamente, enquanto que o comprimento médio das sensilas tricoides curvadas foi diferente para o F9. Essa variação na quantidade de sensilas antenais entre as populações é, possivelmente, uma plasticidade fenotípica, característica importante para a adaptação de espécies a variações ambientais. Esse trabalho representa um estudo preliminar na tentativa de se estudar a variação nos órgãos sensoriais entre diferentes populações de A. robusta.

New species of Tetramorium Mayr (Hymenoptera: Formicidae) from Puebla State, Mexico

Tetramorium notomelanum sp. n. is described from the Tehuacán Valley, state of Puebla, México. Its distribution and relation with other species of the tortuosum-group is discussed. The new species of Tetramonium is described from workers, and distinguished from others of the group by several characters: i) black coloration of the body; ii) size: T. notomelanum sp. n. is smaller than T. hispidum (Wheeler), T. mexicanum Bolton and T.spinosum (Pergande), but larger than T. bicolorum Vásquez-Bolaños and T. placidum Bolton; iii) length of the hairs of the dorsal of the head are equal to the diameter of eye; iv) the length of the hairs on the scape and tibiae less than the width of the appendage where they are located. This is the second species of the tortuosum group of Tetramorium found in the State of Puebla, and the fourth recorded in Mexico.

Behavioral and olfactory antennal responses of Solenopsis geminata (Fabricius) (Hymenoptera: Formicidae) workers to their dufour gland secretion

Behavioral and electrophysiological tests were performed to evaluate the responses of workers of the ant Solenopsis geminata (Fabricius) from different size categories to Dufour gland extracts. Morphometric measures based in head widths across eyes were used to determine worker sizes. Trail following response of different worker sizes to Dufour gland extract from workers of different sizes was assessed. For each worker size category olfactory responses to Dufour gland extracts were determined using electroantennography (EAG). Gas chromatography and mass spectrometry (GC-MS) were used to determine the chromatographic profile of Dufour gland secretion for each worker size. Morphometric measures permitted to classify the workers of S. geminata as large, medium and small workers. Medium S. geminata workers displayed a significantly higher behavioral response to Dufour gland extracts produced by medium size workers. Similarly, medium workers showed a significantly higher EAG response to Dufour gland extracts produced by medium sized workers. Chromatographic profile of Dufour gland secretions produced by workers showed that each size category exhibited a characteristic profile of the three main components considered as potential trail pheromone constituents. This work showed that medium workers of S. geminata exhibited a high trail-following behavior as well as a high antennal response to Dufour gland secretion. This and their relative abundance in field foraging areas, suggest that medium-sized workers are specialized in foraging activities.

Se efectuaron pruebas comportamentales y electrofisiológicas para evaluar las respuestas de obreras de Solenopsis geminata (Fabricius) de diferentes tamaños a extractos de la glándula de Dufour. Se usaron medidas del ancho de la cabeza para determinar el tamaño de las obreras. Se evualuó la respuesta de seguimiento de ruta de obreras de diferentes tamaños a extractos de la glándula de Dufour proveniente de obreras de diferentes tamaños. Para cada grupo de obrera de determinado tamaño se le determinó la respuesta olfatoria por medio de electroantenografía (EAG). Se utilizó Cromatografía de Gases acoplada a Espectrometría de Masas (GC-EM) para determinar el perfil cromatográfico de la secreción de la glándula de Dufour para cada grupo de obreras. Las medidas morfométricas permitieron clasificar a las obreras de acuerdo a su tamaño en grandes, medianas y pequeñas. Las obreras medianas de S. geminata exhibieron una respuesta comportamental alta a los extractos glandulares de hormigas medianas. Las obreras medianas mostraron también una alta respuesta antenal a los extractos de obreras medianas. El perfil cromatográfico de la secreción de la glándula de Dufour producida por obreras muestra que cada tamaño exhibió un perfil característico de los tres componentes potenciales como feromona de ruta. Concluimos que las obreras de tamaño mediano exhibieron altas respuestas tanto comportamentales como olfatorias a la secreción de la glándula de Dufour. Lo anterior y el hecho de que sean las más abundantes en el área de forrajeo sugieren que este grupo de obreras está especializado en actividades de forrajeo.

El género neotropical Brachymyrmex Mayr (Hymenoptera: Formicidae) en la Argentina. III: redescripción de las especies: B. aphidicola Forel, de B. australis Forel y B. constrictus Santschi / The neotropical genus Brachymyrmex Mayr (Hymenoptera: Formicidae) in Argentina. III. redescription of species: B. aphidicola Forel, B. australis Forel & B. constrictus Santschi

Se redescriben las especies del género Brachymyrmex Mayr: Brachymyrmex aphidicola Forel, (n.stat.); B. australis Forel y B. constrictus Santschi. Se acompañan las descripciones de obrera, hembra y macho, con ilustraciones de los principales caracteres morfológicos utilizados en la identificación. Se agregan nuevas localidades de distribución en la Argentina.

Three species of the genus Brachymyrmex: B. aphidicola Forel, (n.stat.); B. australis Forel y B. constrictus Santschi are redescribed hereafter. Descriptions and drawings of main morphological characters of gynes, males and workers are given. New characters are used to differentiate species, mainly based on male head morphology and genitalia. New Argentine localities are added to the known distribution.

Dufour glands in the hymenopterans (Apidae, Formicidae, Vespidae): a review

Associated to the sting apparatus of the aculeate hymenopterans is found the poison gland, originated from the glands associated to the ovipositor of the non-aculeate hymenopterans and the less derived Dufour gland, homologue of the coletterial gland of other insects, and found in all hymenopteran females. The Dufour gland functions is mostly uncertain in hymenopterans but in ants it is involved with communication and defense and in non social bees with the nest building and protection. In wasps possibly with kin-recognition. Differences in morphology and chemical composition of the gland secretion were observed among species, in the same species, between the castes in the social species and among individual of the same caste playing different tasks or belonging to different nest. Its original function of egg-protective substance producing, or favoring the oviposition, appear to have been replaced or complemented in hymenopterans by the production of semiochemicals with function in communication

Morphological changes in the ommatidia of an ant in the day and night states

Morphological changes in dioptric structures, in the position of screening pigments and in the microvillar arrangement of the rhabdom were observed in Atta sexdens ant onmatidia exposed to different ligh/dark schedules. During the day there was a funneling of the crystalline cone and the pigments were close to the rhabdom. At night the crystalline cone became thicker and shorter than in the day state and the pigments moved away from the rhabdom. Endogenous control for these changes was demonstrated in ants kept in continuous darkness. A small but significant contribution of extraocular brain structures to the modulation of pigment position was also demonstrated