Reduvius personatus (Hemiptera: Reduviidae) in a community of Oaxaca state, Mexico

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Reduvius personatus Linnaeus, 1758 is also frequently called the “masked hunter” due to the ability of nymphs to camouflage themselves with a range of materials found in their environment, such as dust, lint, and sand, which mimic the presence of the predatory nymphs and makes them difficult to detect. Camouflaging is a behavior absent in adults that are uniformly black or sometimes dark brown (Weirauch 2006). There is a great variety of entomophagous insects that attack kissing bugs (Hemiptera: Triatominae), including predators of the genus Reduvius as Reduvius senilis and Reduvius personatus, that were reported as active predators of the North American kissing bug, Triatoma protracta (Ryckman and Ryckman 1967). It is frequently mentioned as an important domiciliary predator that destroys the bed bug and other insects of the house. Early reports about the predacious bugs being responsible for limiting populations of triatomines have been documented (Ryckman and Ryckman 1967). The bugs of the subfamily Triatominae are of great medical and epidemiological importance because they are vectors of Trypanosoma cruzi, the etiologic agent of Chagas disease. Due to the limited efficacy of drugs for treating the chronic phase of infection (Clayton 2010), one of the most important components to control the disease is the vector. However, insecticides have not solved the problem of infected Triatominae, and there has been an increased interest in alternative forms of control. Recently, some virus, bacteria, and mites have been considered for controlling the T. cruzi infection of the vector populations (Beard et al. 1993, Azambuja et al. 2004, 2005, Martínez-Sánchez et al. 2007).

Our study was conducted in San Mateo del Mar (16°12′N, 94°59′W) at an altitude of 10 m). This community is located in the Istmo de Tehuantepec region in the state of Oaxaca in southern Mexico. The weather in this region is warm, with short thermal oscillations and a mean annual temperature of 27.4° C. Rain occurs in summer and early fall. As part of a study aimed at the search for triatomines, R. personatus was collected and we also included the search of this insect in the same houses. Three visits were conducted during 2010: in the spring, summer, and winter periods. Sixty houses were selected randomly using the collecting man/hour method in domestic and peridomestic areas (Oliveira 1997). Reduvius searches were done manually using flashlights and were identified according to Lent and Wygodzinsky (1979) and Furman and Catts (1982).

In only one house out of sixty dwellings analyzed (1.6%), three adults (two female and one male) and one 5th instar nymph of R. personatus were found. In this house, only two nymphs of M. phyllosomus were collected, but in contrast we found more than twenty triatomine bugs in other houses (Villalobos et al. 2011). The predators were collected only in summer during three visits. Both species came from domestic areas within approximately 2 m of a principal house, in a room used as a kitchen. They were found under wood piles and the 5th instar nymph was covered with dust. A couple of R. personatus were maintained in the laboratory at 28 ± 2° C and 60% RH. The other R. personatus specimens were frozen for future studies. Initially, adult triatomines of different species as M. longipennis (synonymy Triatoma longipennis), M. phyllosomus, and Triatoma infestans were offered to R. personatus, however these were not fed upon. When 3rd, 4th, and 5th instar nymphs were offered, however, the predators only fed on the 3rd and 4th instars. Each week, two nymphs were placed with the predators until they fed. When the predator was about to feed, the stylets were inserted through a suture on the neck while its legs held the body of triatomine tightly. If the nymphs molted inside in the flask with the predator, any part of the body (genital, abdomen) was attacked. These insects survived approximately 70 days. The female laid 30 eggs, which did not hatch.

Reduviidae, or assassin bugs, are among the most common families of Hemiptera in the world (Forero 2008). Species of this family are mostly predatory, although Triatominae are hematophagous and are important as vectors of T. cruzi. In several countries, successful vector control programs have been carried out, but in other areas where insecticides were applied, the bugs developed resistance in the absence of repeated exposure to pyrethroids, the main compound used in vector control programs for Chagas disease since the mid-1980s (Petherick 2010). Other alternatives to vector control could be explored. Some reports of the presence of Reduvius and Triatominae have been documented for Mexico. Ryckman and Ryckman (1967) reported the presence of R. senilis together with species of triatomines (Triatoma recurva, Triatoma sinaloensis, Triatoma rubida, Triatoma protracta nahuatlae, and M. phyllosomus (synonymy T. phyllosoma)) in burrows of Neotoma in some localities of Sinaloa. No field data have been reported for the presence of R. personatus in Mexico, and for first time, this bug was collected sympatric with M. phyllosomus in a community of Oaxaca State. Although the presence of R. senilis with M. phyllosomus has been described, we suspect that there was a misidentification of the Triatominae species, because it has been reported only in the state of Oaxaca (Villalobos et al. 2011).

Even though only one house was infested with R. personatus, it is important to consider that the least number of M. phyllosomus was collected in this house. In field studies of triatomines, there is no mention of the presence of predators either due to the absence of these or there being little interest in the search. However, in the field, assassin bugs could be regulating them along with mites and ants. In this study, associations between predator-prey in San Mateo del Mar community were made because both bugs were located in the same house and not elsewhere, occupying the same niche and suggesting that R. personatus could be regulating the bug populations. In the other houses where triatomines were collected, high indexes of crowding of 21.7% (triatomines captured/number of houses positive for triatomine × 100) and infestation of 11.7% (houses positive for triatomine/number of houses examined × 100,) were reported (Villalobos et al. 2011). This suggests that every infested house had at least 20 triatomines, in contrast with only two nymphs of M. phyllosomus found with R. personatus. This type of association between triatomine-reduviidae has not been widespread in the field and it is important to conduct further studies to determine the actual importance of R. personatus as a predator of triatomines.

Interestingly, the predator bug was collected in one house but not in other nearby houses with the same building materials. This house was nearer to the field and the predator probably came to this area and settled when it found available food. The growth of human populations and the invasion of wild areas have destroyed the natural habitats of many insects including triatomines, prompting them to colonize the nearby dwellings. In this colonization process other insect species are also forced to move in search of food and stable conditions; the sympatric presence of R. personatus and M. phyllosomus in only one house could be the result of this initial displacement.

Some reports considered cliff faces or bridges as R. personatus nesting sites and locations that are excellent for the hibernation and survival (Ryckman and Ryckman 1967). The proximity of the house to sylvatic area, the period of the year when the bugs were collected, and the presence of only a nymph, suggest that R. personatus was probably attracted for the food but still not established in the house.

When different species of triatomines were offered as food, we found that R. personatus had no preference for a particular species but only fed on nymphal instars and not adults, suggesting that R. personatus is not specific to the type of triatomine species but only to the stage. Unfortunately, we were not able to establish the conditions of maintenance (temperature and humidity) and although they oviposited, the eggs were not viable, and after about two months this predator died. In the case of R. senilis, developmental studies were conducted in an incubator at the same conditions (28° C, 50–60% RH) and fed exclusively on Triatoma (Ryckman and Ryckman 1967) as for R. personatus maintained in the laboratory, showing that the requirements for each species are different. Other conditions could be evaluated for raising R. personatus under laboratory conditions to study how the control of triatomine populations can be realized.

Acknowledgments

We thank Dr. Alejandro Martínez-Ibarra, Centro Universitario del Sur, Ciudad Guzmán, Jalisco, México for comments on the manuscript. The work was financially supported by the Consejo Nacional de Ciencia y Tecnología (CONACyT), grant number 113985.

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