Abstract Presence of the genus Neoparasitylenchus Nickle, 1967 (Tylenchida, Allantonematidae), parasitizing Harmonia axyridis (Pallas, 1773) (Coleoptera, Coccinellidae) in Argentina. We describe a new species Neoparasitylenchus platense sp. n., which is characterized by having the free living stages lip region flatly rounded, spear slender, faintly knobbed, tail rounded, females with light brown body, stylet not sunken into body, and not prominent, subterminal vulva and anus, obtusely rounded tail end, with a peg-like projection, oviparous, and the males with a little stylet and partially degenerate oesophagus, spicules filiform with widened base, short gubernaculum, leptodera bursa.

Resumen Se cita por primera vez el género Neoparasitylenchus Nickle, 1967 (Tylenchida, Allantonematidae), parásito de Harmonia axyridis (Pallas, 1773) (Coleoptera, Coccinellidae) para Argentina. Se describe la especie nueva Neoparasitylenchus platense sp. n. que se caracteriza por tener en las formas de vida libre la región labial rodeada de una estructura plana, estilete delgado, levemente curvado, apéndice caudal redondeado, hembras con cuerpo marrón claro, estilete no hundido en el cuerpo y no prominente, vulva y ano subterminal, apéndice caudal redondeado, con una proyección en forma de clavija, ovíparos. Los machos con un estilete y un esófago parcialmente degenerados, espículas filiformes con base ensanchada, gubernaculum corto, bursa leptodera.

Resumo Este trabalho apresenta os resultados de uma pesquisa entomonematode parasitando gafanhotos em pastagens da região pampeana, Argentina. Ninfas de Staurorhectus longicornis Giglio-Tos, Laplatacris dispar Rhen de 1939, Dichroplus elongatus Giglio-Tos, 1894 e Metaleptea brevicornis (L.) (Orthoptera: Acrididae) foram coletados. Mermithidae era a única família registrado com sete espécies: Agamermis decaudata Cobb, Steiner and Christie, 1923, Amphimermis bonaerensis Miralles and Camino, 1983, Amphimermis dichroplusi Camino and Lange, 1997, Amphimermis ronderosi Camino and Lange, 1997, Hexamermis coclhearius Stock and Camino, 1992, Hexamermis ovistriata Stock and Camino, 1992, e Longimermis acridophila Camino and imagem, de 1989. Os valores de parasitismo variou entre 1-12%, e intensidade não superar o número de 5,0 nematóides por larva. Os nemátodos observados demonstraram especificidade, não registar as mesmas espécies de parasita em mais do que uma espécie de hospedeiro. A região pampeana constituída uma área com alta diversidade de mermithids onde novas espécies poderiam ser consideradas como agentes bio-reguladores deste incômodos insetos pragas em áreas agrícolas da Argentina.

Abstract This work provides the results of a survey of entomonematodes parasites of grasshoppers in grasslands of the Pampean Region, Argentina. Nymphs of Staurorhectus longicornis Giglio-Tos, Laplatacris dispar Rhen, 1939, Dichroplus elongatus Giglio-Tos, 1894 and Metaleptea brevicornis (L.) (Orthoptera: Acrididae) were collected. Mermithidae was the only family registered with seven species: Agamermis decaudata Cobb, Steiner and Christie, 1923, Amphimermis bonaerensis Miralles and Camino, 1983, Amphimermis dichroplusi Camino and Lange, 1997, Amphimermis ronderosi Camino and Lange, 1997, Hexamermis coclhearius Stock and Camino, 1992, Hexamermis ovistriata Stock and Camino, 1992, and Longimermis acridophila Camino and Stock, 1989. The values of parasitism ranged between 1-12%, and intensity not overcome the number of 5.0 nematodes per larva. The nematodes observed showed specificity, not registering the same species of parasite in more than one host species. The Pampean region constituted an area with high diversity of mermithids where new species could be consider as bioregulator agents of this troublesome insect pests in agricultural areas of Argentina.

Blatticola cristovata n. sp. (Oxyurida, Thelastomatidae) a parasite of the cricket Anurogryllus muticus (De Geer, 1773) (Orthoptera, Gryllidae) from Argentina, is described and illustrated. This is the first species of the genus Blatticola found parasitizing cricket. This new species is characterized in females by having the cuticle annulated through the body length, the mouth opening is subtriangular and surrounded by eight cephalic papillae, the stoma is short with three pairs placed in two rows of cuticular sclerotised plates, amphids in small pore shaped, oesophagus is divided into three parts, anterior cylindrical corpus, isthmus distinct, and basal bulb valved, the nerve ring is situated around the middle of corpus, the intestine is wide broad anteriorly, oval eggs, smooth shell, with a straight side, and the other side with a band running longitudinally. Males with one pair of preanal, one pair of adanal and two pairs of postanal papillae, and the tail appendage short, conical and pointed.

Una nueva especie Blatticola cristovata n. sp. (Oxyurida, Thelastomatidae) parásita del grillo Anurogryllus muticus (De Geer, 1773) (Orthoptera, Gryllidae) en Argentina, se describe e ilustra. Esta es la primera especie del género Blatticola que se encontró parasitando a grillos. Esta nueva especie se caracteriza por tener las hembras la cutícula anillada a lo largo de todo el cuerpo, la abertura bucal triangular rodeada por ocho papilas cefálicas, el estoma corto con tres pares de placas esclerotizadas dispuestas en dos líneas, anfidios pequeños en forma de poro, esofago dividido en tres partes, una anterior con un corpus cilíndrico, un istmo distintivo, y un bulbo basal con valvas, el anillo nervioso situado rodeando el corpus, el intestino ensanchado anteriormente, huevos ovales, de cáscara lisa, con un lado recto y el otro con una cresta longitudinal. Macho con un par de papilas preanal, uno adanal y dos pares de papilas postanales, y apéndice caudal corto, cónico y punteagudo.

Uma espécie nova do gênero Cephalobium (Nematoda, Cephalobiidae), parasita de Anurogryllus muticus (De Geer) (Ortoptera, Gryllidae) de Gorina, La Plata, Argentina, é descrita e ilustrada. Este nematoda pode ser caracterizado por apresentar estoma mais longo que largo, o aparelho glottoideo anisoglottideo e anisomórfico, dividido em duas porções, uma com paredes quitinizadas e a outra com três dentes dorsais simples. O macho possui espículas longas e separadas e o gubernáculo curto sem qualquer projeção. As papilas genitais estão organizadas em cinco pares pós-anais.

A new species of Cephalobium from Gorina, La Plata, Argentina, parasiting nymphs of Anurogryllus muticus (De Geer) (Orthoptera, Gryllidae) is described and illustrated. This nematode can be characterized by having the stoma longer than broad, the glottoid apparatus anisoglottid and anisomorphic, divided into two portions, one with cuticularized walls and the other with three simple dorsal teeth. The male is further characterized by the presence of two long and separated spicules and short gubernaculum without any projection. Genital papillae are arranged in five postanal pairs.

Cameronia laplatae n. sp. found in City Bell, Argentina, parasitizing crickets is described and illustrated. The new species is distinguished from other members of the genus Cameronia by the distribution pattern of the genital papillae in the male. It differs from all congeners mainly in having two pairs preanal y two pairs postanal papillae

Two new species of mermithids (Nematoda: Mermithidae), Gastromermis doloresi n. sp. a parasite of Simulium wolffhuegeli Roubaud and Hydromermis doloresi n. sp. a parasite of S. jujuyense (Paterson & Shannon) from Córdoba, Argentina, are described and illustrated. G. doloresi n. sp. is characterized by having medium sized, pear-shaped and oval amphids, eight hypodermal chords all around the body, cylindrical S-shaped vagina, single long spicule 528 [mi]m, whith teh sculpture tip, three rows of genital papillae in which the middle row contains 17 pre-anal and 9 post-anal papillae, and lateral rows contain 18 papillae. Hydromermis doloresi n. sp. can be distinghished by the following: medium sized, pear-shaped amphids, eight hypodermal chords, a cylindrical, S-shaped vagina, one short curved spicule with sculpture and genital papillae in three rows. The medium ventral row of papillae has 4 double and 9 single pre-anal papillae and 3 double and 6 single port-anal papillae, lateral rows have 18 single papillae each.

Gastromermis cordobensis n. sp (Nematoda: Mermithidae) a parasite of larvae of the blackfly Simulium lahillei Paterson & Shannon (Diptera: Simuliidae) in Argentina, is described. Diagnostic characters of this species include a mouth ventrlly shifted; six cephalic papillae; eigh hypodermal chords; small and pear shaped amphids; a long and S-shaped vagina; a singl spicule, which is long, has non-uniform walls, and a tip with sculpture; three rows of genital papillae, the middle one with 18 pre-anal and 10 post-anal papillae, the lateral rows have 36 papillae each; oval eggs; and post-parasitic juveniles with long thin tails. Pre-parasitic and parasitic juveniles are included in the description.