Biologia, comportamento social e alocação sexual de Digelasinus diversipes (Kirby, 1882) (Hymenoptera, Argidae)

Abstract

ABSTRACT. Biology, social behavior and sex-allocation of Digelasinus diversipes (Kirby, 1882) (Hymenoptera, Argidae). The results of a two-year study of the Neotropical sawfly Digelasinus diversipes are presented. This species is univoltine and common in Estação Ecológica Jataí, a nature reserve of Cerrado vegetation in São Paulo State, Brazil. The larvae feed gregariously on Eugenia glazioviana (Kiaersk.) D. Legrand (Myrtaceae) from November through April. Fusions of different feeding groups were frequent. After the feeding period, larvae congregate and communally construct a cocoon mass (105 cocoons ± 60SD; n = 25) attached to the trunk of the host plant, entering in diapause as prepupae until the beginning of the rainy season in October. The population peak was in December when 62% (n = 2,967) of adult emergence occurred. In experimental conditions, emergence was observed from 6:30 a.m. until 15:00 p.m., but 73.5% (n = 223) of the adults appeared between 9:00 a.m. and 12:00 h. Sex sequence was not observed during emergence but, in a single cocoon mass, males may appear 20 to 40 days earlier than females. After emergence, males may either (1) disperse (early and late in the emergence period; October and November, January and February, respectively) or (2) remain on or near the cocoon mass and mate with newly emerged females (during the emergence peak in December). Copulation lasts 4.28 minutes (±3.4SD; n = 28), and during the day, males may mate with different females (1-8; n = 5); however, females mate only once. Newly emerged females have a mean of 76 mature eggs (± 21SD; n = 19) and oviposited all of them underneath of a single leaf of the host plant. Egg guarding by females lasted only 2 (n = 12) of the 30 days of egg incubation. The female's behavioral repertoire against potential enemies was shorter than that reported for some other sawfly species. Apparently, the female induces necrosis of the leaf tissue that covers the eggs, which forms a hard shelter for the eggs during incubation. Both sexes of D. diversipes do not feed as adults (controlled condition) and have a short life span (5.2 days ± 1.7SD; minimum 1, maximum 11; n = 179). The mean sex ratio was 2.83 (± 0.014SE) in favor of females. Main mortality factors were development defects, lack of food due to intense herbivory, and attack of parasitoids. Parasitoids reared, Lymeon dieloceri (Costa Lima, 1937) (Ichneumonidae), Conura (Spilochalcis) sp. (Chalcididae) and Perilampus sp. (Perilampidae).KEYWORDS. Gregarious feeding; maternal care; Neotropical sawfly; sex ratio; subsocial insect. RESUMO. Biologia, comportamento social e alocação sexual de Digelasinus diversipes (Kirby, 1882) (Hymenoptera, Argidae). São apresentados os resultados de um estudo de dois anos sobre o Symphyta neotropical Digelasinus diversipes. Esta espécie é univoltina e comum na Estação Ecológica Jataí, uma reserva de Cerrado no Estado de São Paulo. As larvas alimentam-se gregariamente em Eugenia glazioviana (Myrtaceae) de novembro a abril. Associações entre grupos de alimenta...

Sawflies out of Gondwana: phylogenetics and biogeography of Argidae (Hymenoptera)

“…However, this general behaviour includes variation within several traits among these genera (defence mechanisms of the female, host plant species, egg location and distribution on leaves, total period of guarding, mass cocoon structures, etc.) (Benson, 1938;de Souza Dias, 1975;de Souza Dias, 1976;Smith, 1992;Ciesla, 2002;Smith & Janzen, 2003;Boraschi et al, 2005). A similar maternal guarding behaviour is also present in some Pergidae (Perga, Pseudoperga, Philomastix, Cladomacra and Syzygonia) (Benson, 1938;Shinohara, 1986;Schiff, 2004;Schmidt et al, 2006).…”

“…In subclade XIIb, Sericoceros shows maternal care (Ciesla, 2002), while for its sister group Subsymmia the life history is unknown. In subclade XIIc, Themos clearly shows maternal care and subsocial behaviour, together with the genera Pachylota, Dielocerus and Digelasinus, while for Topotrita and Mallerina, the biology is unknown (de Souza Dias, 1975;de Souza Dias, 1976;Smith, 1992;Ciesla, 2002;Smith & Janzen, 2003;Boraschi et al, 2005).…”

“…9). One probable ancestral trait in this behaviour complex present in Sericoceros and Themos (sister group of the remaining taxa in clade XIIc) is that females lay the eggs directly on the leaf epidermis and in circular/oval egg clusters instead of inside the mesophyll of the leaves and scattered over the entire leaf as in Dielocerus and Digelasinus (Benson, 1938;de Souza Dias, 1975;de Souza Dias, 1976;Smith, 1992;Ciesla, 2002;Smith & Janzen, 2003;Boraschi et al, 2005). Larvae of clade XII share the presence of two or more non-eversible coxal glands (Malagón-Aldana et al, 2021b); however, it is unknown if this feature is related to gregarious or subsocial behaviour.…”

Life history of Aneugmenus merida Smith (Hymenoptera: Tenthredinidae) in the Venezuelan Andes

“…A diversity of patterns of population dynamics have been observed in other Neotropical sawfly species, e.g. Digelasinus diversipes (Kirby) (Hymenoptera: Argidae) is an univoltine species which can go into diapause for the whole 7-9 month dry season of Estação Ecológica Jataí in São Paulo State, Brazil (Boraschi et al 2005), while Dielocerus diasii Smith (Hymenoptera: Argidae) can go through four developmental cycles in one year (Días 1976).…”

“…Contributions to the knowledge of three Brazilian species of Argidae are worth mentioning (Dias 1976, Penteado-Dias 1991, Boraschi & Del Lama 2004, Boraschi et al 2005. Dutra (2003) studied cases of bovine intoxication caused by ingestion of sawfl y larvae, and reported on the biology of Perreyia fl avipes Konow (Hymenoptera: Pergidae).…”