First report of Engytatus varians (Distant, 1884) (Heteroptera: Miridae: Dicyphini) in Eastern Uruguay and preliminary test on its feeding habits

The aim of this work is to report the unprecedented presence in Uruguay of Engytatus varians (Distant, 1884), a predator of several pests of Solanaceae, to present its main morphological features and some facts of its biology, and to provide a key for the identification of the Dicyphini species registered in the country. The presence of this predator in our region is of great interest for the development of future research works related to biological pest control and the potential interaction thereof with other predaceous mirids.

Effects of sex ratio on different biological parameters of Engytatus varians (Distant) (Hemiptera: Miridae) adults and their offspring: prey preference for Bactericera cockerelli (Sulcer) (Hemiptera: Triozidae)

In the present study, the influence of three sex ratios (1:1, 1:2, and 1:3; female:male) of the mirid Engytatus varians (Distant) (Hemiptera) on different biological parameters and on its offspring was evaluated. The prey preference of different developmental stages of this predator for different nymphal instars (N) of Bactericera cockerelli (Sulcer) (Hemiptera: Triozidae) was also evaluated. The fertility was significantly higher (24 nymphs/female) in the 1:3 sex ratio than in the 1:1 and 1:2 sex ratios (14 and 16 nymphs/female, respectively). The females in the 1:1 and 1:2 sex ratios lived 1.14 and 1.43 days more (27 and 28 days, respectively) than those in the 1:3 sex ratio (26 days). The nymphs derived from the females of the three sex ratios (first filial generation, F1) had five instars and a duration of 17 or 18 days. The ratio of the F1 generation females was not affected by the sex ratio of their parents. In choice tests, independent of whether the preys were placed on a single or multiple tomato (Solanum lycopersicum L.) leaflets, the consumption of females and males and N3, N4, and N5 nymphs of E. varians on B. cockerelli, generally showed the order of N2>N3>N4>N5. In conclusion, the findings revealed in this study can help to improve the rearing methodology for increasing populations of E. varians. In addition, they can serve as a guideline for releasing this predator in times when there is an abundance of early instar nymphs of B. cockerelli.

Predation by Engytatus varians (Distant) (Hemiptera: Miridae) on Bactericera cockerelli (Sulcer) (Hemiptera: Triozidae) and two Spodoptera species

Predation by Engytatus varians (Distant) adults on different development stages of the prey species Bactericera cockerelli (Sulcer) (egg, second, and third nymphal instars), Spodoptera exigua (Hübner) and Spodoptera frugiperda (J. E. Smith) (egg, first, and second larval instars) was evaluated using tomato (Solanum lycopersicum L.) leaflets or plants. These insects are the primary pest of several agriculturally important crops. The influence of E. varians age on the predation capacity was also analysed. Engytatus varians females consumed significantly more B. cockerelli eggs and nymphs than males. Additionally, female predators consumed significantly more second than third instar prey at two predator ages, while males consumed significantly more the second instar than third instar prey at all predator ages. In most of the cases, females also consumed significantly more S. exigua and S. frugiperda eggs than males; however, in terms of larvae consumption, this difference was observed only in some predator ages. Females consumed more the first than second instar S. exigua than males, whereas this behaviour was only observed in males when the predators were 15 and 17 days old. No significant differences were observed in the consumption of first and second instar of S. frugiperda for both sexes of the predators. Predator age did not cause any systematic effects on the predation rates of any prey species. Based on these results, we confirmed that E. varians has potential as a biological control agent for B. cockerelli and also for the Spodoptera species bioassayed.

Do nymphs and adults of three Neotropical zoophytophagous mirids damage leaves and fruits of tomato?

The predators Macrolophus basicornis (Stal), Engytatus varians (Distant) and Campyloneuropsis infumatus (Carvalho) consume large numbers of tomato pests such as Bemisia tabaci (Gennadius) and Tuta absoluta (Meyrick). However, they are zoophytophagous and feed on plant parts as well. We evaluated the type and effect of injury caused by nymphs and adults of these mirids on tomato seedlings and fruit in the absence of prey. For each mirid species, seedlings were exposed to groups of 20 nymphs or adults for 72 h, and fruits were exposed for 48 h to groups of four nymphs or adults. Type and the number of injury on stems, petioles and leaflets of tomato seedlings and fruits were recorded after removal of insects. Nymphs and adults of these mirids caused necrotic rings on the leaflets, but no injury was observed on stem and petioles. The necrotic rings on leaflets consisted of blemishes, characterized by feeding punctures surrounded by a yellowish, bleached area. The number of necrotic rings did not exceed one per individual mirid and seedlings developed normally. Nymphs also caused feeding punctures on tomato fruit, but in even lower numbers than on leaflets. Two weeks after the start of the experiment the tomato fruit still looked fresh and feeding punctures had disappeared. Adults did not cause any injury to tomato fruit. The results indicate that nymphs and adults of these zoophytophagous mirids cause little injury to tomato seedlings and fruit, even when present in high densities and in the absence of prey, making them interesting candidates for biological control.

Primer registro de Engytatus varians (Distant) (Hemiptera: Heteroptera: Miridae) en México y su depredación sobre Bactericera cockerelli (Šulc) (Hemiptera: Triozidae): una revisión de su distribución y hábitos

Engytatus varians (Distant) (Hemiptera: Miridae) es una especie zoofitófaga debido a que se alimenta de las plantas hospederas y de los insectos que viven en ellas como áfidos, moscas blancas, pseudocóccidos y lepidópteros. Actualmente, esta especie presenta una amplia pero imprecisa distribución. En este trabajo se reporta por primera vez la presencia de E. varians en México depredando ninfas del psílido del tomate, Bactericera cockerelli (Šulc) (Hemiptera: Triozidae) bajo condiciones de invernadero. En promedio, una ninfa de cuarto estadio de E. varians se alimentó de 46% de las ninfas de tercer estadio de B. cockerelli en un periodo de 24 h. Este resultado muestra que este depredador podría representar un candidato potencial para el manejo del psílido del tomate. También se incluye información de su distribución, plantas hospederas y presas.