Abstract During a search for parasites in fishes from Iguazu River, Argentina, a nymph of pentastomid was found encysted on mesenteries of Phalloceros harpagos. The 28S rDNA and COI mt-DNA were used to compare with the sequences deposited in the GenBank. Pentastomid nymphs belong to the subfamily Diesingiinae (Sebekidae) for having chloride cell pores distributed in a single row per annulus; also, the hooks and rows of spines of our material differ to other genera. Present specimens are most likely Diesingia sp., having 63-74 annuli, a U shaped oral cadre with fibers closing anteriorly and a peg like extension of the oral cadre. The 28S rDNA analysis places our samples into a sister group of Alofia sp., but the COI mt-DNA situate them on the base of the clade. In conclusion, our pentastomid positively belongs to Diesingia sp., however, indisputable assignation requires a reliable description of the nymph, or the availability of sequences linking nymphs and adults, which even could provide evidence of a new hitherto undescribed genus. Aditionally, the systematic position of Sebekia oxycephala previously described by P. harpagos is discussed on the basis of our results, allowing us to suggest a re-assignation of such specimens to the genus Diesingia.

The first record of the genus Ocnaea Erichson, 1840 (Diptera, Acroceridae) is presented for the Argentine Republic and the first record of this family parasitizing a spider of the genus Catumiri Guadanucci 2004 (Mygalomorphae, Theraphosidae). Some observations of the biological cycle of the fly parasitizing the tarantula Catumiri argentinense (Mello-Leitão, 1941) are reported.

Se presenta el primer registro del género Ocnaea Erichson, 1840 (Díptera, Acroceridae) para la República Argentina y el primer registro de esta familia parasitando una araña del género Catumiri Guadanucci 2004 (Mygalomorphae, Theraphosidae). Se dan a conocer algunas observaciones del ciclo biológico de la mosca parasitando la tarántula Catumiri argentinense (Mello-Leitão, 1941).

Abstract In the present study, data on the interaction between wasp specimens of the species Epipompilus platensis Roig Alsina, 2017 (Hymenoptera, Pompilidae) and spiders of the species Ariadna mollis (Holmberg 1876) (Araneae, Segestriidae) are presented for the first time. Present in the localities of Punta Lara (Partido de Ensenada) and José Hernández (Partido de La Plata), both belonging to the province of Buenos Aires. Several specimens of A. mollis were collected on april 2015, and those that presented an egg or a small larva attached to the back of the abdomen were selected. They were kept under observation in a bioterium until completing the development of the wasp's adult state. Of the total spiders collected, 9.6% were parasitized by wasps. Of that percentage, four larvae of E. platensis reached the adult stage (three females and one male). The results obtained contribute to the knowledge of a new interaction between wasps and spiders.

Resumen En el presente estudio se dan a conocer por primera vez, datos sobre la interacción entre ejemplares de avispas de la especie Epipompilus platensis Roig Alsina, 2017 (Hymenoptera, Pompilidae) y arañas de la especie Ariadna mollis (Holmberg 1876) (Araneae, Segestriidae), en las localidades de Punta Lara (partido de Ensenada) y José Hernández (partido de La Plata), ambas pertenecientes a la provincia de Buenos Aires. Se recolectaron varios ejemplares de A. mollis en el mes de abril del 2015, y se seleccionaron aquellos que presentaban un huevo o una pequeña larva adherida al dorso del abdomen. Se mantuvieron bajo observación en bioterio hasta completar el desarrollo al estado adulto de la avispa. Del total de las arañas colectadas, el 9.6% se encontró parasitado por avispas. De ese porcentaje, cuatro larvas de E. platensis llegaron al estado adulto (tres hembras y un macho). Los resultados obtenidos contribuyen al conocimiento de una nueva interacción entre avispas y arañas.

Four species of Epipompilus occur in Argentina: E. platensis sp. n., E. tucumanus Evans, E. jocosus Evans, and E. excelsus (Bradley), the last two being new records for this country. The new species E. platensisis described based on specimens from Buenos Aires in Argentina and Santa Catarina in Brazil. The incorrect association of sexes in the original description of E. jocosusis clarifed. Descriptions, taxonomic notes, illustrations and a key to species, are presented.

Cuatro especies de Epipompilus están presentes en la Argentina: E. platensis sp. n., E. tucumanus Evans, E. jocosus Evans, y E. excelsus (Bradley), siendo las dos últimas nuevos registros para este país. La nueva especie E. platensis se describe sobre especímenes de Buenos Aires en la Argentina y de Santa Catarina en Brasil. Se clarifca la incorrecta asociación de sexos en la descripción original de E. jocosus. Se presentan descripciones, notas taxonómicas, ilustraciones y una clave para las especies.

RESUMEN Las arañas son consideradas de importancia para estudios de biodiversidad, conservación y sucesión. Presentan facilidad para dispersarse y establecerse en nuevos hábitats por lo que son buenos colonizadores de territorios insulares. La familia de arañas Theridiidae es una de las más diversas, representada por una gran variedad morfológica, etológica y ecológica. En Argentina no existen trabajos referidos a terídios de territorios insulares, por lo tanto, este trabajo consiste en el primer registro de la familia en estos ambientes. La Isla Martín García es una Reserva Natural e Histórica que se ubica en el sector noreste del Río de La Plata y presenta variabilidad ambiental y florística. Para analizar la riqueza específica, abundancia relativa y diversidad alfa y beta de terídios se realizaron muestreos durante tres años consecutivos mediante red de golpeo y muestreo manual. Se capturaron un total de 1173 individuos, pertenecientes a nueve géneros y 21 morfoespecies. La especie más abundante en todos los ambientes fue Cryptachaea hirta (61,68%). La selva fue el ambiente con mayor diversidad (H' = 1,9, J = 0,67) (S = 16), brindando una vasta vegetación, con amplios recursos para la subsistencia de estas arañas. La isla no correspondería a un área de importancia respecto a la singularidad de especies. Se encontraron tres nuevos registros para Argentina: C. altiventer, Theridion positivum y T. tinctorium.

ABSTRACT Spiders are considered important for studies of biodiversity, conservation and succession. They readily disperse and become established in new habitats and are considered good colonizers of islands. The Theridiidae is one of the most diverse spider families, characterized by great morphological, ethological and ecological diversity. In Argentina, there are no studies of island theridiids, therefore, this study comprises the first record of the family in these environments. The Martín García Island is a Natural and Historical Reserve located in the northwest of the La Plata River and presents environmental and floristic variability. In order to analyse the species richness, relative abundance and alpha and beta diversity of theridiids, sampling was performed over three consecutive years, by beating net and manual sampling. We recorded 1173 spiders, belonging to 9 genera and 21 morphospecies. The most abundant species in all environments was Cryptachaea hirta (61.68%) The forest was the habitat with highest diversity (H’ = 1.9, J = 0.67) (S = 16), providing extensive vegetation, with vast resources for the survival of these spiders. The island is not an important area with regard to species singularity. Three new records were found for Argentina: C. altiventer, Theridion positivum and T. tinctorium.

The aim of this study was to identify entomopathogenic fungi infecting spiders (Araneae) in a protected area of Buenos Aires province, Argentina. The Araneae species identified was Stenoterommata platensis. The pathogens identified were Lecanicillium aphanocladii Zare & W. Gams, Purpureocillium lilacinum (Thom) Luangsa-ard, Houbraken, Hywel Jones & Samson and Ophiocordyceps caloceroides (Berk & M.A. Curtis). This study constitutes the southernmost records in the world and contributes to expanding the knowledge of the biodiversity of pathogenic fungi of spiders in Argentina.

Two new species of Plesiopelma Pocock, 1901 from northern Argentina are described and diagnosed based on males and habitat descriptions are presented. Males of Plesiopelma paganoi sp. nov. differ from most of species by the absence of spiniform setae on the retrolateral face of cymbium, aspect of the palpal bulb. Plesiopelma aspidosperma sp. nov. differs from most species of the genus by the presence of spiniform setae on the retrolateral face of cymbium and it can be distinguished from P. myodes Pocock, 1901, P. longisternale (Schiapelli & Gerschman, 1942) and P. rectimanum (Mello-Leitão, 1923) by the separated palpal bulb keels and basal nodule of metatarsus I very developed. It differs from P. minense (Mello-Leitão, 1943) by the shape of the palpal bulb and basal nodule on metatarsus I well developed. Specimens were captured in Salta province, Argentina, inhabiting high cloud forests of Yungas eco-region.

Dos nuevas especies de Plesiopelma Pocock, 1901 del norte de Argentina son diferenciadas y se describen en base a ejemplares machos y se presentan descripciones de los ambientes. Machos de Plesiopelma paganoi sp. nov. difieren de la mayoría de las especies por la ausencia de setas espiniformes en la cara retrolateral del cymbium, por la forma del órgano palpar. Plesiopelma aspidosperma sp. nov. difiere del resto de las especies por la presencia de setas espiniformes en la cara retrolateral del cymbium y se distingue de P. myodes Pocock, 1901, P. longisternale (Schiapelli & Gerschman, 1942) y P. rectimanum (Mello-Leitão, 1923) por las quillas del bulbo separadas y el nódulo basal del metatarso I muy desarrollado. Se diferencia de P. minense (Mello-Leitão, 1943) por la forma del órgano palpar y el nódulo basal del metatarso I desarrollado. Los especímenes se capturaron en la provincia de Salta, Argentina, habitando nuboselvas de altura en la eco-región de Yungas.

A new species of Eupalaestrus Pocock, 1901 from northern Argentina is described and illustrated. Males and females of Eupalaestrus larae sp. nov. differ from those all other species of the genus by the color with distinct two parallel longitudinal stripes on the femora, patellae, tibiae and one longitudinal stripe reaching half of metatarsi; the presence of a thickened femur and tibia IV; a straight embolus of the male palpal bulb and retrolateral keel pronounced. Specimens were captured in Chaco province, inhabiting unflooded flat grasslands open areas inside forest in transitional Chaco eco-region.

Una nueva especie de Eupalaestrus Pocock, 1901 del norte de Argentina es descripta e ilustrada. Machos y hembras de Eupalaestrus larae sp. nov. difieren del resto de las especies de género por el color con dos líneas paralelas longitudinales distintivas en fémures, patelas y tibias y una línea longitudinal alcanzando la mitad del metatarso; la presencia del fémur y tibia IV ensanchados; un émbolo recto en el bulbo palpal del macho y una quilla retrolateral pronunciada. Los especímenes se capturaron en la provincia de Chaco, habitando un pastizal abierto no inundable dentro de bosques en la eco-región de Chaco transicional.