View metadata, citation and similar papers at core.ac.uk brought to you by CORE Brazilian Journal of Biology https://doi.org/10.1590/1519-6984.184595provided by Repositório Institucional da Universidade de Brasília ISSN 1519-6984 (Print) ISSN 1678-4375 (Online) Biotic potential and reproductive parameters of Spodoptera cosmioides (Walker) (Lepidoptera: Noctuidae) in the laboratory A. Spechta* and V. F. Roque-Spechtb aEmbrapa Cerrados, BR 020, Km 18, CP 08223, CEP 73310-970, Planaltina, DF, Brasil bFaculdade UnB Planaltina, Universidade de Brasília – UnB, Área Universitária 1, Vila Nossa Senhora de Fátima, CEP 73345-010, Planaltina, DF, Brasil *e-mail: [email protected] Received: August 27, 2017 – Accepted: December 26, 2017 – Distributed: August 31, 2019 (With 6 figures) Abstract In this study we evaluate the biotic potential and reproductive parameters of Spodoptera cosmioides (Walker, 1858) under controlled conditions (25 ± 1 °C, 70 ± 10% RH and 14 hour photophase). Females, on average, (14.433 days) did not live significantly longer than their male counterparts (13.100 days). The mean durations of the pre-oviposition, oviposition and post-oviposition periods were 2.767, 10.600 and 1.067 days, respectively. The mean fecundity of females was 5,073.533 eggs and the mean fertility was 5,021.027 larvae. On average, females copulated 1.167 times. Fecundity was positively correlated with the number of copulations (r = 0.583, P <0.001). The number of copulations, however, was negatively correlated whit the duration of the pre-oviposition (r = -0.560, P = 0.007) and oviposition (r = -0.479, P = 0.048) periods, and overall longevity (r = -0.512, P = 0.031). The biotic potential was estimated at 6.547 x 1021 individuals/female/year. The net reproductive rate (Ro) was 2,193.722 times per generation and the mean generation time (T) was 46.407 days. The intrinsic rate of increase (rm) was 0.166, with a finite rate of increase (λ) of 1.180, per week. Keywords: armyworm, development, fecundity, reproduction, spermatophore. Potencial biótico e parâmetros reprodutivos de Spodoptera cosmioides (Walker) (Lepidoptera: Noctuidae) em laboratório Resumo Neste estudo avaliamos o potencial biótico e parâmetros reprodutivos de Spodoptera cosmioides (Walker, 1858) em condições controladas (25 ± 1 °C, 70 ± 10% UR e 14 horas de fotofase). Em média, as fêmeas (14,433 dias) não viveram significativamente mais do que os machos (13,100 dias). A duração média dos períodos de pre-oviposição, oviposição e pós-oviposição foram 2,767; 10,600 e 1,067 dias, respectivamente. A fecundidade média das fêmeas foi de 5.073,533 ovos e a fertilidade média foi de 5.021,027 larvas. Em média, as fêmeas copularam 1,167 vezes. A fecundidade correlacionou-se positivamente com o número de cópulas (r = 0,583; P <0,001). Entretanto, o número de cópulas correlacionou-se negativamente com a duração dos períodos de pré-oviposição (r = -0,560; P = 0,007), oviposição (r = -0,479; P = 0;048) e a longevidade (r = -0,512; P = 0,031). O potencial biótico foi estimado em 6,547 x 1021 indivíduos/fêmea/ano. A taxa líquida de reprodução (Ro) foi de 2.193,722 vezes por geração e o tempo médio de cada geração (T) foi de 46,407 dias. A taxa intrínseca de crescimento (rm) foi 0,166, com uma taxa finita de aumento (λ) de 1,180, por semana. Palavras-chave: lagarta militar, desenvolvimento, fecundidade, reprodução, spermatóforo. 1. Introduction The genus Spodoptera Guenée, 1852 (Lepidoptera: Studies on the host-plant associations, temporal Noctuidae) or “armyworms” is one of the most important groups and spatial distribution, morphology, and biology of of owlet moth pests around the world. Spodoptera cosmioides S. cosmioides have highlighted its importance as a pest of (Walker, 1858) occurs from Panama to southern South several crops, its low susceptibility to Bt protenis and to America (Pogue, 2002) and was considered a synonym the entomopathogenic fungus Metarhizium rileyi (Farlow) of S. latifascia (Walker, 1856) (Poole, 1989) until Silvain Samson (e.g., Specht and Corseuil, 2002; Bavaresco et al., and Lalanne-Cassou (1997). 2002, 2003, 2004; Specht et al., 2005; Zenker et al., Braz. J. Biol. 2018, Ahead of Print 1/7 1 Specht, A. and Roque-Specht, V.F. 2007, 2010; Fronza et al., 2011; Bergamasco et al., 2013; to count their numbers. Dead females were dissected to Cabezas et al., 2013; Fronza et al., 2013; Bernardi et al., determine the number of spermatophores they had received 2014; Specht and Roque-Specht, 2016). from males during copulation. This study complements a previous publication on the We count the realized fecundity (only eggs laid per immatures of S. cosmioides (Specht and Roque-Specht, female), fertility (number of hatched larvae per female) 2016) and is part of a project where the main species of and longevity for females and males. The duration of the armyworms are being studied under identical controlled pre-oviposition, post-oviposition and oviposition periods conditions. These studies aim to compare the biology of were determined considering the pairing, in the day of these species, establish biological patterns and differences. adult emergence. To estimate fertility, we determined Thus, in this work we compare the biological data of the viability of 87 egg masses (N = 9,563 eggs) taken S. cosmioides with three species already studied in same from four mated couples, including the first and the last conditions: S. albula (Walker, 1857), S. eridania (Stoll, egg masses. Each egg cluster was placed in a Petri dish, 1782) and S. dolichos (Fabricius, 1794) (Montezano et al., which was lined with filter paper moistened with distilled 2013a, b, 2014a, b, 2015, 2016) and other works about water until larval eclosion. All evaluated egg masses were S. cosmioides (Santos et al., 1980; Habib et al., 1983; from females that had at least one spermatophore in the Bavaresco et al., 2002, 2003, 2004; Zenker et al., 2007; bursa copulatrix. The determination of the presence of Cabezas et al., 2013). spermatophores was made on dead females to confirm that they had been fertilized during the experiment. 2. Material and Methods All biological parameters were analyzed using descriptive statistics. The fecundity and longevity of both The experiments were carried out in a climate-controlled room (25 ± 1 °C, 70 ± 10% RH and a 14 hour photophase). sexes and the duration of pre-oviposition, oviposition and Observations were carried out daily. The insects used in post-oviposition periods were correlated (Pearson Product the experiment came from a first generation of caterpillars Moment Correlation) with the number of matings of each collected from Fevillea cordifolia Linn. (Cucurbitaceae) in couple. Owing to the high correlation of the parameters the city of Planaltina, Federal District, Brazil (15°36’16.85”S; with respect to the number of matings, only the overall 47°43’06.57”W, 1020 m a.s.l) (Specht and Roque-Specht, averages of longevity were compared using the t-test 2016). assuming unequal variances, at a significance level of To avoid the effects of variations in the pupal weight 5%. Between-couple comparisons of the pre-oviposition, on the reproductive characteristics of the adult (Tisdale oviposition, longevity and fecundity were performed and Sappington, 2001; Specht et al., 2016), and also to using ANOVA, with the number of spermatophores as standardize the procedure and avoid hurting the insects factors, and the means were separated by Tukey’s test at while their pupae was still soft, all pupae were weighed 5% probability in SPSS program version 10.0. on the second day after metamorphosis, and only adult After gathering the biological parameters, the Biotic females from pupae weighing between 0.632 and 0.674g, Potential (BP) was calculated considering the resistance and adult males from pupae weighing between 0.591 and of the environment as being null. We used the equation 0.648 g, were used in the experiment. Likewise, to avoid described in Silveira Neto et al. (1976), BP = (sr * d) n the effects of the age of the adults on their capacity to - er, where: (sr) sex ratio is number of females divided copulate (Kehat and Gordon, 1975; Rogers and Marti by number of females plus number of males; (d) viable Junior, 1994), couples were formed with adults that individuals per female consisting of the number of eggs emerged on the same date. per female (or fecundity) multiplied by total survival; Adults were kept in pairs (n = 30) within cylindrical (n) number of generations per year or 365 days divided plastic containers (10 cm in diameter and 15 cm high) with by the total lifespan; and (er) environmental resistance, long filter paper strips attached to stimulate oviposition. in this case considered null. The tops of the containers were closed with plastic film and The biotic potential and fertility life table were developed the bottoms were closed with Petri dishes (10.5 cm diameter) using data from the immature stages of S. cosmioides lined with filter paper. The adult diet was composed of honey (survival and duration of eggs, larvae, prepupae and pupae) (10g), sorbic acid (p.a. - Sigma-Aldrich) (1g), methylparaben reared in accordance with the methodology of Specht and (p.a. - Sigma-Aldrich) (1g), sucrose (p.a. Merck) (60g), and Roque-Specht (2016). The data on the table is graphically distilled water (1000 mL) (Hoffmann-Campo et al., 1985). presented by plotting the probability of survival values All components were dissolved in distilled water and the at the midpoint of each time interval, (survival rate - lx), resulting solution was kept under refrigeration (7 °C) until and the total number of eggs per female, per week, from it was used. Pilsen beer was added to the solution daily which females hatched (specific fertility - mx).