On the Nesting Biology of Pirhosigma Giordani Soika (Hymenoptera, Vespidae, Eumeninae), with Special Reference to the Use of Vegetable Matter
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Revista Brasileira de Entomologia http://dx.doi.org/10.1590/S0085-56262013005000044 SHORT COMMUNICATION On the nesting biology of Pirhosigma Giordani Soika (Hymenoptera, Vespidae, Eumeninae), with special reference to the use of vegetable matter Marcel G. Hermes1, Alexandre Somavilla2 & Bolívar R. Garcete-Barrett3 1Laboratório de Sistemática e Biologia de Hymenoptera, Departamento de Biologia, Universidade Federal de Lavras, Caixa Postal 3037, 37200–000 Lavras-MG, Brazil. [email protected] 2Programa de Pós Graduação em Entomologia, Instituto Nacional de Pesquisas da Amazônia, Av. André Araújo 2936, 96060–001 Manaus-AM, Brazil. 3Laboratório de Biologia Comparada de Hymenoptera, Departamento de Zoologia, Universidade Federal do Paraná, Caixa Postal 19020, 81531–980 Curitiba-PR, Brazil. ABSTRACT. On the nesting biology of Pirhosigma Giordani Soika (Hymenoptera, Vespidae, Eumeninae), with special refer- ence to the use of vegetable matter. The use of vegetable matter in nest building is not widespread among the Eumeninae, and is reported for the first time for the two species of potter wasps Pirhosigma superficiale and P. limpidum. These wasps make mostly spherical mud nests over which they attach small pieces of unmasticated plant matter. Use of plant fragments in this group of wasps is interpreted as camouflage behavior. KEYWORDS. Eumenini; Insecta; nest construction; phylogeny. Eumeninae, along with Euparagiinae and Stenogastrinae, precluding that character from use in natural classification of is one of the least known subfamilies of Vespidae. Despite the subfamily. However, the phylogenetic hypothesis recovered being the largest vespid subfamily, with more than 3,500 spe- by Hermes et al. (in press) shows that a large clade of eumenine cies described (Pickett & Carpenter 2010), knowledge of wasps (i.e. the tribe Eumenini) presents the elegant construc- eumenine biology is scarce and scattered throughout the lit- tion behavior of remarkable mud pots, lending the popular name erature over the past 200 years, compared to the Stenogastrinae, “potter wasps”, applied to the subfamily as a whole. the Polistinae and the Vespinae, which comprise the eusocial Pirhosigma Giordani Soika, 1978 is a small genus of soli- vespid clade (Carpenter 1982; Pickett & Carpenter 2010). The tary wasps composed of seven recognized species, all of them Eumeninae, however, are valuable for studies concerning the restricted to the Neotropical region. Few data have been ever evolution of eusociality, since their behavior ranges from soli- published regarding the nesting biology of the species within tary to primitively social. this genus (Giordani Soika 1978), but it is widely accepted The morphological complexity of the Eumeninae has long that all of them build mud pots as the remainder Eumenini. prevented any attempt at a natural classification for the group One record indicates that a species of Pirhosigma (identi- (Parker 1966; Carpenter & Cumming 1985). Until recently, fied as Pirhosigma sp.) nests in pre-existing cavities (Pires no tribal classification has been widely adopted by the work- et al. 2012). This is perhaps an isolated record, which could ers on the group, despite some proposals by early authors indicate plasticity in the nesting behavior of this genus, such (e.g. Ashmead 1902). Hermes et al. (in press) have investi- as observed for Pachodynerus de Saussure for example, but gated the phylogenetic relationships among the main lineages the possibility of wasp misidentification cannot be disre- of the Eumeninae, and proposed the first tribal division of garded. The present work constitutes the first reliable bio- the subfamily based on cladistic methods. As a result, three logical information for species of Pirhosigma, namely P. tribes were recognized and some biological extrapolations superficiale (Fox, 1899) and P. limpidum Giordani Soika, may be inferred, especially regarding nesting biology. 1978. This study also discusses the uncommon use of veg- Species of Eumeninae may be classified into three types etable particles in the construction of the nest within mem- regarding nesting biology: excavators, renters and builders bers of the tribe Eumenini, which may help to understand (Maindron 1882; Iwata 1976). These types are initially appeal- the phylogenetic relationships among species of Pirhosigma ing for use in eumenine classification, but the behavioral plas- and closely related eumenine genera. ticity observed for several species makes them polymorphic The observations on P. superficiale were conducted in (Cooper 1979; Krombein 1979). The nest architecture of the countryside in the municipality of Santa Cruz do Sul eumenines shows plasticity as well (Evans & Matthews 1974), (29°40’21”S and 52°24’03”W), Rio Grande do Sul State, Revista Brasileira de Entomologia 57(4): 433–436, December 2013 434 Hermes et al. southern Brazil. Nest construction was observed during April four cells. In some cases, as in species of Hypodynerus de 2007. The voucher specimen of the studied wasp is depos- Saussure (Claude-Joseph 1930), Brachymenes Giordani Soika ited in the Coleção Entomológica da Universidade de Santa (Camillo 1999) (both placed in the tribe Odynerini) and Cruz do Sul (CESC) under the record number CESC 19920. Pachymenes de Saussure (M.G. Hermes, unpublished; an- Nests of P. limpidum were collected in the municipality of other Eumenini), extra mud layers may be added to the cells Nova Friburgo (22º16’55”S and 42º31’52”W), Rio de Janeiro in which cases the individual pots are no longer distinct. This State, Brazil, on July 2007. Voucher specimens are depos- condition may well serve as protection against potential en- ited at the Universidade Federal de Lavras, Minas Gerais. emies, but its homologous nature relative to the use of veg- The female of P. superficiale built its nest with mud, at- etable particles to camouflage the nests must be tested. taching the cells to a human construction (Figs. 1–4). The nest The use of vegetable matter in eumenine nest construction consisted of two cells disposed laterally to each other; both is not a new phenomenon for the subfamily as a whole. It seems cells remained exposed and had an average height of about 18 that most species reported for the genus Zethus Fabricius in- mm. The cells were mostly rounded, but presented a conical corporate leaf material into cell partitions. Species of Zethus protuberance on their lower portion, which probably is an arti- (Zethoides) may construct their entire cells with masticated fact to aid in rainwater runoff, since the nest is susceptible to vegetable matter and resin, and the nests may be shared by weather conditions. After the cells were completed, the wasp several females tending their own brood (see Bohart & Stange began flying back and forth from the nest; upon returning, the 1965 and references therein). Use of plant material may in female wasp brought along small pieces of unmasticated veg- fact characterize Zethini as a whole: Discoelius Latreille, etable matter. These vegetable particles were cut from a spe- Ischnocoelia Perkins and Protodiscoelius Dalla Torre also use cies of Poaceae, and were usually dry and longer than the nest vegetable matter for cell partition (van der Vecht & Fisher 1972; height, being attached to the upper part of the cells and to the Claude-Joseph 1930; van der Vecht 1981, respectively), and building wall (Fig. 4). The vegetable particles then covered Psiliglossa Saunders and Raphiglossa Saunders use pith (van the entire cells, possibly serving as a camouflage strategy by der Vecht & Fisher 1972). the wasp to avoid recognition by potential natural enemies. Pirhosigma was recovered in a large clade that contains Jayakar & Spurway (1965) suggested that Delta conoideum only Neotropical taxa in the phylogenetic hypothesis presented (Gmelin, 1790) (cited as Eumenes emarginatus conoideus) also by Hermes et al. (in press), along with several genera, among camouflage the nests to prevent recognition of the cells by them Cyphomenes Giordani Soika and Pararhaphidoglossa von parasites. In this case, the wasp plastered (they used the term Schulthess. Besides their morphological similarity, biological crépissage following Roubaud (1916)) the nest walls with information may serve as additional support for their close additional lumps of mud which extended from the nest peak relationship. Cooper (2012) mentioned that the mandibles of to the substrate on which it was constructed. A drawing pre- Pararhaphidoglossa are shorter and more bristly than in other sented by Maindron (1882: Pl. 1, figure 6) also suggested the Eumenini, probably “adapted for the manipulation of vegetable use of extra mud on the cell walls to form an irregular surface. fragments that are attached to the nest”. More recently, Coo- The use of vegetable particles was also observed for P. per (2013) described and illustrated the nests of three species limpidum. In this case, the construction of the nests was not of Pararhaphidoglossa (namely P. bicarinata Giordani Soika, observed, but the cells were collected and reared (Figs. 5 and P. confluenta (Fox) and P. imitatrix Giordani Soika), all of them 6). The female wasps attached the mud cells to a metal wire being covered with vegetable particles. Bertoni (1918) reported fence, which was then cut for nest removal. The cells were the construction of a nest by a female of Cyphomenes anisitsii built separately, and we have no evidence whether they were (Brèthes) (misidentified in that paper as Eumenes infernalis built