Crickets and mole crickets are important herbivores of the Pampas biogeographic region in Argentina, constituting a serious problem in crops and pastures soils because of their eating habits (^{Aragón 2006}, Bentancourt and Scatoni 2010). Entomopathogenic nematodes are commonly used as biological control agents against several insect pests. However, a large number of nematodes belonging to various families (^{Adamson and van Waerebeke 1992}, ^{Marchissio and Miralles 1993}, ^{Jex et al. 2006}) show a parasitic relationship with their hosts and are frequently found at the intestines of these insects during prospecting studies in the laboratory.

The present study analyzes the intestinal nematofauna of the Orthoptera species Anurogryllus muticus De Geer, 1773, and Neocurtilla claraziana Saussure, 1874 from pastures of La Plata, Buenos Aires, Argentina, as part of a survey work conducted to isolate entomopathogenic nematodes against these insect pests.

Insects were recovered during a survey in grasslands from La Plata city, Buenos Aires, Argentina (34°56'00" South, 57°57'00" West) during 2015-2017, with a garden shovel. They were dissected in the laboratory to determine the presence of nematodes which were transferred to a fixative of 50 % (v/v) aqueous triethanolamine formalin for 48 hs and placed in 100 % triethanolamine formalin, before transfer to glycerol for slow evaporation (^{Seinhorst 1959}). Nematodes were identified by morphological and morphometrical features of females and males following ^{Adamson and van Waerebeke (1992)}. The prevalence as the number of hosts infected with a particular species of parasite/number of hosts examined from the same parasitized species expressed in percentage was determined.

The results of the survey reported the cricket Anurogryllus muticus (Gryllidae) (n = 738) and the mole cricket Neocurtilla claraziana (Gryllotalpidae) (n = 317). Eleven nematode species belonging to the families Thelastomatidae, Travassosinematidae, Cephalobidae, Rhabditidae, and Plectidae were isolated from the intestine of both hosts (Table 1) with the largest number of species (n = 7) in N. claraziana; in A. muticus only four individuals were reported. Blatticola cristovata Achinelly and Camino, 2007 was the only species found in both hosts. Males were observed only in four of the eleven species recovered (B. cristovata, Cephalobium nitidum Camino and Reboredo, 2000, Cameronia arecoensis Marchissio and Miralles, 1987, and Cruznema tripartitum (Linstow, 1906), Zullini, 1882). Cephalobium nitidum, C. tripartitum and Plectus parietinus, Bastian, 1865 are reported for Argentina for the first time. Plectus parietinus was found once in the intestine of A. muticus. Because this species is a free living nematode, we believe that having been found in the intestine of crickets could be due to a random event during the feeding of the insect.

Table 1 Intestinal nematodes isolated from A. muticus and N. claraziana. 

According to the results expressed above, the diversity in N. claraziana was slightly superior to that in A. muticus. Regarding A. muticus it was not found a great diversity of entomonematodes compared to another soil pest cricket of Buenos Aires Province such as G. laplatae (^{Camino and de Villalobos 2002}). In G. laplatae there have been citing six species of Cephalobium, two species of the order Oxyurida, Cameronia laplatae, and Neyraiella distinctus (Camino and de Villalobos 2002) and the mermithid, Hex-amermis macrostomata (Camino and Stock 1994).

On the other hand, N. claraziana presents a mayor number of species respect to another mole cricket from Buenos Aires Province, Scapteriscus borelli Nickle, 1992, where only Steinernema scapterisci (Rhabditida) was found (^{Stock 1992}). The findings of this study contribute to have a better understanding about the biodiversity status of insect parasitic nematodes of the region.