Body size variations of pupae and adults in the sexual dimorphism of the sweet potato leaf miner Bedellia somnulentella (Zeller, 1847) (Lepidoptera: Bedelliidae)Morphometrics is used to characterize intraspecific and interspecific variations, distinguishing species within the same genus, such as Trichogramma spp. Westwood, 1833 (Hymenoptera: Trichogrammatidae), populations of Cinara cupressi (Buckton, 1881) (Hemiptera: Aphididae), and sexual dimorphism in pupae and adults of Rhinochenus stigma L., 1758 (Coleoptera: Curculionidae) (Querino and Zucchi, 2004; Fonseca et al., 2014; Ruiz et al., 2014).
The microlepidopteran Bedellia somnulentella (Zeller, 1847) (Lepidoptera: Bedelliidae), originating in Eurasia, was first reported in the Americas in 1862 and has since spread worldwide, achieving cosmopolitan pest status (Clemens, 1862; Steyn et al., 2020). The genus Bedellia (Stainton, 1849), with 16 described species, is the only genus in the family Bedelliidae (Meyrick, 1880) (Van Nieukerken et al., 2011). The morphological characteristics of B. somnulentella include translucent neonate caterpillars with laterally tubercular bodies and reddish coloration in the last instar. The pupae remain attached to silken threads on the plant leaf's underside or other structures close to the host, not enclosed by a cocoon or pupal chamber. The pupal coloration is brown and darkens near emergence (Clemens, 1862). The body size of B. somnulentella adults is approximately 4 mm, with a bronze-yellow coloration, filiform antennae, and fringed hind wings (Shorey and Anderson, 1960).
Bedellia somnulentella has been reported in Brazil as one of the most important pests of Ipomoea batatas (L.). Lam. (Convolvulaceae) aerial parts, its primary commercial host. This pest is a leaf miner that feeds on the leaf mesophyll of young and mature leaves, reducing photosynthetic area and tuberous root development (Shorey and Anderson, 1960; Santos et al., 2018). Therefore, this study aimed to differentiate female and male pupae and adults of B. somnulentella using body morphometric measurements.
Bedellia somnulentella was reared in the Cell Biology Laboratory of the Universidade Federal dos Vales do Jequitinhonha e Mucuri (UFVJM), Campus JK, in Diamantina, Minas Gerais state, Brazil, in wooden cages measuring 30 × 30 × 30 cm with screened sides and a glass lid, at room temperature.
Caterpillars of B. somnulentella were fed with leaves of I. batatas, obtained from the greenhouse of the Crop Science sector of UFVJM. Adults of this species were fed with a 5% sugar solution, soaked in cotton tufts and placed in Petri dishes (Parrella and Kok, 1977).
One hundred pupae were obtained from laboratory rearing and photographed, measured, and isolated separately in 2.0 mL Eppendorf microtubes for adult emergence. A total of pupae were selected (15 females and 15 males) and confirmed using the method of Pinheiro et al. (2024), and, after emergence, all adults were also measured. Images of pupae and adults were obtained using a Canon EOS Rebel 850D camera coupled to an AXOC NDPL 1(2x) B0B4T93Z7V lens (ASIN) on a LEICA EZ4 stereomicroscope (Leica Microsystems) with a millimeter microscope calibration slide (TCM-H) and resolution scales of 0.1 mm, using the ImageJ program (National Institutes of Health, Bethesda, USA) (Rueden et al., 2017).
Bedellia somnulentella pupae are obtect (Rafael et al., 2012), which allows observation of the appendages, including the right forewing of the adult stage. This allowed their measurement while still in the pupal stage. Thus, all parameters were obtained in both pupae and adults of both sexes. The morphological characters measured were head length and width (HL and HW), eye length and width (EL and EW), eye distance (ED), antennal length (AL), thorax length and width (TL and TW), forewing length (FL), abdominal length (Al), length of the last abdominal tergite (LLAT), distance between the cremasters (CD), body length (BL), and wingspan (Wi).
The data on the morphometric characters of pupae and adults of B. somnulentella were analyzed using a t-test (P < 0.05) in R Core Team (2021) (University of Auckland, New Zealand).
Among the characters measured in the head of B. somnulentella pupae, head width (HW) and eye width (EW) showed significantly higher values in female pupae; at the same time, antennal length (AL) was greater in males (Table 1). The other characters, such as head length (HL), eye length (EL), distance between eyes (ED), tergite length (TL), thorax width (TW), and distance of cremasters (CD), did not differ statistically between females and males, according to the t-test (P < 0.005) (Table 1).
Regarding the body characteristics of B. somnulentella pupae, body length (BL), right forewing length (FL), and abdominal length (Al) were significantly greater in female pupae. Only the length of the last abdominal tergite (AT) was significantly greater in male pupae, according to the t-test (P < 0.05) (Table 1).
Antenna length (AL) was significantly longer in males compared to females of B. somnulentella. The other characters measured on the head, such as head length (HL) and head width (HW), and distance between eyes (DE), did not show statistical differences between the sexes of this moth based on the t-test (P < 0.05) (Table 1).
The body traits measured in B. somnulentella varied between males and females. The wingspan of female adults (Wi) was greater than that of male adults, and it was the most evident trait for differentiating the sexes of this insect among the measured traits. The thorax (TL) and abdominal width (AW) of female adults were greater than those of males. The abdominal length (Al) of females was greater than that of males. The body length (BL) of females of B. somnulentella was greater than that of males. The length of the last abdominal tergite (LLAT) was greater in males and differed statistically by the t-test (P < 0.05) (Table 1).
Bedellia somnulentella belongs to the superfamily Yponomeutoidea Stephens, 1829, which comprises families of 10 microlepidoptera (Van Nieukerken et al., 2011). Analyses revealed that female B. somnulentella pupae were larger than male pupae. A similar pattern was observed in Syssphinx molina (Cramer, 1780) (Lepidoptera: Saturniidae), a member of Bombycoidea Latreille, 1802, whose female pupae exhibited larger body dimensions (Batista et al., 2013). In contrast, in the superfamily Noctuoidea Latreille, 1809, specifically in Spodoptera frugiperda (J.E. Smith, 1797) (Lepidoptera: Noctuidae), the opposite trend was observed, with male pupae reaching greater body length than female pupae (Navasero and Navasero, 2020).
Analyses of thirteen characters in both sexes of B. somnulentella pupae revealed mixed variation between head and body measurements. This pattern was similar to that observed for the morphometric characters of the head, body, and appendages of R. stigma, including head length and width, eye length, dimensions of the antennal segments (scape, pedicel, and flagellum), and other body proportions, which did not show significant differences between males and females (Fonseca et al., 2014). In both cases, accurate sex identification required dissection of the pupae close to emergence (Fonseca et al., 2014).
Females of B. somnulentella had greater body and abdominal length than males, demonstrating sexual dimorphism. This pattern was also observed in other insects, such as Demotispa neivai (Bondar, 1940) (Coleoptera: Chrysomelidae) (Martínez et al., 2013) and Oncideres dejeani Thomson, 1868 (Coleoptera: Cerambycidae) (Seffrin et al., 2006). Among the parameters evaluated, body length is the most efficient for detecting sex differences, given that larger females are common in Lepidoptera and are widely reported in other insect groups. The greater mobility of males, in turn, may justify the smaller body size, as described for Deinacrida rugosa Buller, 1871 (Orthoptera: Anostostomatidae) (Kelly et al., 2008). In species such as Dicyphus agilis Uhler, 1877 (Hemiptera: Miridae) and D. neivai, the main characters used to distinguish the sexes were abdomen and body width, in addition to body, thorax, and head lengths, which were generally longer in females (Martínez et al., 2013; Plata-Rueda et al., 2015). However, in D. neivai, males had longer thorax and abdomen, a pattern also recorded for males of B. somnulentella. In contrast, in R. stigma, body length did not vary between sexes, despite sexual dimorphism in other characters (Fonseca et al., 2014).
Females of B. somnulentella present extended abdomen than males, a pattern similar to that recorded in D. neivai and D. agilis, whose females also exhibit a larger abdomen. However, in D. neivai, males had a more extended abdomen (Martínez et al., 2013; Plata-Rueda et al., 2015).
The antennae of male B. somnulentella are longer than those of females, demonstrating sexual dimorphism. This pattern also occurs in Telchin licus Drury, 1773 (Lepidoptera: Castniidae) of the superfamily Cossoidea (Leach, 1815), Carabus coriaceus L., 1758, and Carabus preslii Dejean, 1830 (Coleoptera: Carabidae), in which males have longer antennae, although the number of flagellomeres is identical between sexes (Triana et al., 2020). In B. somnulentella, this condition was observed, suggesting that longer antennae are associated with greater male efficiency in mate search (Talarico et al., 2011). This relationship between antennal length and reproductive behavior is widely documented in Carabidae, where males utilize agility to search for females (Talarico et al., 2007). In contrast, in Trichospilus pupivorus Ferriere, 1930 (Hymenoptera: Eulophidae), females have longer antennae, configuring a distinct pattern of sexual dimorphism (Silva et al., 2016).
The largest wingspan recorded in females of B. somnulentella corresponds to the pattern described for Phyllocnistis citrella (Stainton, 1856) (Lepidoptera: Gracillariidae) of the superfamily Gracillarioidea Stainton, 1854 (Kim et al., 2015), Boloria pales Denis & Schiffermüller, 1775, and Boloria napaea Hoffmannsegg, 1804 (Lepidoptera: Nymphalidae) of the superfamily Papilionoidea Latreille, 1802. In these cases, females require greater flight capacity to explore food resources and select suitable oviposition sites, while males remain predominantly in the habitat, directing their activity toward mate search (Ehl et al., 2018).
The number of measured traits that indicated dimorphism between female and male pupae of B. somnulentella was variable. These were the width of the head and eye in female pupae, and the length of the antennae in male pupae. Regarding measurements of the body and its appendages, the length of the forewing, abdominal tergites, and body were greater in female pupae, while the length of the last abdominal tergite was greater in male pupae.
Regarding body measurements in adults, morphometric variations of the head were not very pronounced, with only antennal length differing, greater in males of B. somnulentella. Regarding body measurements, they varied significantly, with the length and width of the thorax, wingspan, abdominal length and body length being greater in females, while the length of the last abdominal tergite was greater in males of B. somnulentella.
Morphometry can help determine sexual dimorphism in B. somnulentella. In pupae, characteristics of the head, body, and appendages stand out. In adults, dimorphism is mainly evidenced through body measurements. Some of these characteristics have been little explored or are novel in Lepidoptera.
Acknowledgements
To the Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) Finance code 001, Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) and the Fundação de Amparo à Pesquisa do Estado de Minas Gerais (FAPEMIG) project APQ-04955-23.
Data availability statement
The research data is available upon prior request via email to the corresponding author.
References
-
BATISTA, T.F.V., LUNZ, A.M., ROSÁRIO, V.D.S.V., LEMOS, L.J.U., PROVENZANO, R.S. and MONTEIRO, E.D.S., 2013. Biological and morphometric aspects and rearing of Syssphinx molina (Cramer) (Lepidoptera: Saturniidae), a defoliator of parica tree. Acta Amazonica, vol. 43, no. 2, pp. 191-196. https://doi.org/10.1590/S0044-59672013000200009
» https://doi.org/10.1590/S0044-59672013000200009 - CLEMENS, B., 1862. North American microlepidoptera. Proceedings of the Entomological Society of Philadelphia, vol. 1, pp. 147-151.
-
EHL, S., HOSTERT, K., KORSCH, J., GROS, P. and SCHMITT, T., 2018. Sexual dimorphism in the alpine butterflies Boloria pales and Boloria napaea: differences in movement and foraging behavior (Lepidoptera: Nymphalidae). Insect Science, vol. 25, no. 6, pp. 1089-1101. https://doi.org/10.1111/1744-7917.12494 PMid:28618194.
» https://doi.org/10.1111/1744-7917.12494 -
FONSECA, A.J., MENEZES, C.W.G., SANTOS, C.A., ASSIS JÚNIOR, S.L., FONSECA, A.G. and SOARES, M.A., 2014. Morfometria de pupas e adultos de Rhinochenus stigma Linnaeus, 1758 (Coleoptera: Curculionidae). Revista Árvore, vol. 38, no. 1, pp. 25-30. https://doi.org/10.1590/S0100-67622014000100002
» https://doi.org/10.1590/S0100-67622014000100002 -
KELLY, C.D., BUSSIERE, L.F. and GWYNNE, D.T., 2008. Sexual selection for male mobility in a giant insect with female-biased size dimorphism. The American Naturalist, vol. 172, no. 3, pp. 417-423. https://doi.org/10.1086/589894 PMid:18651830.
» https://doi.org/10.1086/589894 -
KIM, D.S., CHOI, C.W., LEE, S. and BYUN, B.K., 2015. Taxonomic notes on Phyllocnistis citrella (Lepidoptera: Gracillariidae) with genital structures and DNA barcode from Korea. Journal of Asia-Pacific Biodiversity, vol. 8, no. 4, pp. 295-297. https://doi.org/10.1016/j.japb.2015.10.005
» https://doi.org/10.1016/j.japb.2015.10.005 -
MARTÍNEZ, L.C., PLATA-RUEDA, A., ZANUNCIO, J.C., LEITE, G.L.D. and SERRÃO, J.E., 2013. Morphology and morphometry of Demotispa neivai (Coleoptera: Chrysomelidae) adults. Annals of the Entomological Society of America, vol. 106, no. 2, pp. 164-169. https://doi.org/10.1603/AN12013
» https://doi.org/10.1603/AN12013 - NAVASERO, M.M. and NAVASERO, M.V., 2020. Life cycle, morphometry and natural enemies of fall armyworm, Spodoptera frugiperda (J.E. Smith) (Lepidoptera: Noctuidae) on Zea mays L. in the Philippines. Journal of the International Society for Southeast Asian Agricultural Sciences, vol. 26, pp. 17-29.
-
PARRELLA, M.P. and KOK, L.T., 1977. The development and reproduction of Bedellia somnulentella on Hedge Bindweed and Sweet Potato. Annals of the Entomological Society of America, vol. 70, no. 6, pp. 925-928. https://doi.org/10.1093/aesa/70.6.925
» https://doi.org/10.1093/aesa/70.6.925 -
PINHEIRO, R.A., CABRAL, M.J.S., GIORDANI, S.C.O., ZANUNCIO, J.C., SERRÃO, J.E., SANTOS, C.A. and SOARES, M.A., 2024. Sex dimorphism in pupae and adults of the specialist Ipomoea batatas defoliator Bedellia somnulentella (Lepidoptera: Bedelliidae). Neotropical Entomology, vol. 53, no. 6, pp. 1374-1378. https://doi.org/10.1007/s13744-024-01197-8 PMid:39172303.
» https://doi.org/10.1007/s13744-024-01197-8 -
PLATA-RUEDA, A., MARTÍNEZ, L.C., ZANUNCIO, J.C. and SERRÃO, J.E., 2015. Morphology and morphometry of adults of Dicyphus agilis (Hemiptera: Miridae). Annals of the Entomological Society of America, vol. 108, no. 3, pp. 333-338. https://doi.org/10.1093/aesa/sav022
» https://doi.org/10.1093/aesa/sav022 -
QUERINO, R.B. and ZUCCHI, R.A., 2004. Morphometric analysis in Trichogramma (Hymenoptera: Trichogrammatidae) species. Neotropical Entomology, vol. 33, no. 5, pp. 583-588. https://doi.org/10.1590/S1519-566X2004000500007
» https://doi.org/10.1590/S1519-566X2004000500007 -
R CORE TEAM, 2021 [viewed 16 Oct 2025]. R: A language and environment for statistical computing Vienna: R Foundation for Statistical Computing. Available from: https://www.R-project.org/
» https://www.R-project.org/ - RAFAEL, J.A., MELO, G.A.R.D., CARVALHO, C.J.B.D., CASARI, S.A. and CONSTANTINO, R., 2012. Insetos do Brasil: diversidade e taxonomia Ribeirão Preto: Holos Editora.
-
RUEDEN, C.T., SCHINDELIN, J., HINER, M.C., DEZONIA, B.E., WALTER, A.E., ARENA, E.T. and ELICH, T., 2017. ImageJ2: ImageJ for the next generation of scientific image data. BMC Bioinformatics, vol. 18, no. 1, pp. 529. https://doi.org/10.1186/s12859-017-1934-z PMid:29187165.
» https://doi.org/10.1186/s12859-017-1934-z -
RUIZ, C., LANFRANCO, D., CARRILLO, R. and PARRA, L., 2014. Morphometric variation on the cypress aphid Cinara cupressi (Buckton) (Hemiptera: Aphididae) associated to urban trees. Neotropical Entomology, vol. 43, no. 3, pp. 245-251. https://doi.org/10.1007/s13744-014-0204-2 PMid:27193620.
» https://doi.org/10.1007/s13744-014-0204-2 -
SANTOS, M.M., SOARES, M.A., SILVA, I.M., FONTES, P.C.R. and ZANUNCIO, J.C., 2018. First record of the sweet potato pest Bedellia somnulentella (Lepidoptera: Bedelliidae) in Brazil. The Florida Entomologist, vol. 101, no. 2, pp. 315-316. https://doi.org/10.1653/024.101.0224
» https://doi.org/10.1653/024.101.0224 -
SEFFRIN, R.D.C.A.S., COSTA, E.C., COUTO, M.R.M. and LOPES, S.J., 2006. Medidas morfométricas de fêmeas e machos de Oncideres dejeani Thomson, 1868 (Coleoptera: Cerambycidae). Ciência Rural, vol. 36, no. 5, pp. 1313-1316. https://doi.org/10.1590/S0103-84782006000400044
» https://doi.org/10.1590/S0103-84782006000400044 -
SHOREY, H.H. and ANDERSON, L.D., 1960. Biology and control of the morning-glory leaf miner, Bedellia somnulentella, on sweet potatoes. Journal of Economic Entomology, vol. 53, no. 6, pp. 1119-1122. https://doi.org/10.1093/jee/53.6.1119
» https://doi.org/10.1093/jee/53.6.1119 -
SILVA, I.M.D., PEREIRA, K.D.S., SPRANGHERS, T., ZANUNCIO, J.C. and SERRÃO, J.E., 2016. Antennal sensilla and sexual dimorphism of the parasitoid Trichospilus pupivorus (Hymenoptera: Eulophidae). Microscopy and Microanalysis, vol. 22, no. 4, pp. 913-921. https://doi.org/10.1017/S1431927616011314 PMid:27411894.
» https://doi.org/10.1017/S1431927616011314 -
STEYN, L.A.I., GEERTSEMA, H., MALAN, A.P. and ADDISON, P.A., 2020. Review of leaf-mining insects and control options for their management, with special reference to Holocacista capensis (Lepidoptera: Heliozelidae) in vineyards in South Africa. South African Journal of Enology and Viticulture, vol. 41, no. 2, pp. 218-232. https://doi.org/10.21548/41-2-4081
» https://doi.org/10.21548/41-2-4081 -
TALARICO, F., BRANDMAYR, P., GIGLIO, A., MASSOLO, A. and ZETTO BRANDMAYR, T., 2011. Morphometry of eyes, antennae and wings in three species of Siagona (Coleoptera: Carabidae). ZooKeys, vol. 100, no. 100, pp. 203-214. https://doi.org/10.3897/zookeys.100.1528 PMid:21738413.
» https://doi.org/10.3897/zookeys.100.1528 -
TALARICO, F., ROMEO, M., MASSOLO, A., BRANDMAYR, P. and ZETTO, T., 2007. Morphometry and eye morphology in three species of Carabus (Coleoptera: Carabidae) in relation to habitat demands. Journal of Zoological Systematics and Evolutionary Research, vol. 45, no. 1, pp. 33-38. https://doi.org/10.1111/j.1439-0469.2006.00394.x
» https://doi.org/10.1111/j.1439-0469.2006.00394.x -
TRIANA, M.F., FRANCA, P.H., QUEIROZ, A.F., SANTOS, J.M., GOULART, H.F. and SANTANA, A.E., 2020. Morphological, chemical and electrophysiological investigations of Telchin licus (Lepidoptera: Castniidae). PLoS One, vol. 15, no. 4, pp. e0231689. https://doi.org/10.1371/journal.pone.0231689 PMid:32298345.
» https://doi.org/10.1371/journal.pone.0231689 -
VAN NIEUKERKEN, E.J., KAILA, L., KITCHING, I.J. ...and ZWICK, A., 2011. Order Lepidoptera Linnaeus, 1758. In: Z.Q. ZHANG, ed. Animal biodiversity: an outline of higher-level classification and survey of taxonomic richness New Zealand: Magnolia Press, pp. 212-221, Zootaxa, vol. 3148. https://doi.org/10.11646/zootaxa.3148.1.41
» https://doi.org/10.11646/zootaxa.3148.1.41
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