HYM. RES. J. Vol. 3, 1994, pp. 133-143 Colony Densities and Preferences for Nest Habitats of Some Social Wasps in Mato Grosso State, Brazil (Hymenoptera, Vespidae) IVONE R. DiNIZ AND KlNITI KlTAYAMA DepartamentodeZoologia, Institutede Biologia UniversidadedeBrasilia, 70910-900Brasilia DF, BRAZIL — Abstract Studiesofcolonydensitiesandpreferencesfornest habitatsofsomesocialwaspswereconductedincerrado vegetation inSouthernMatoGrossostateinCentral Brazil.Waspcolonydensitieswereestimated inthreehabitats(campo umido,cerradosensu-strictoand gallery forest). Regarding thewasp nesthabitatspreferences, we found 100coloniesof30 speciesin 15genera nestinginsixdifferenthabitatsinSouthernMatoGrosso. InNorthernMatoGrosso,basedonRichards (1978),wefound 199coloniesof51 speciesin14generanestinginsixdifferenthabitats.Considering bothregionstogether, wecameoutwith 299coloniesof61 species in 16genera nesting in ninedifferent habitats. INTRODUCTION METHODS ANDSTUDY AREA Theeffectivenessandefficacyofpredationby- The studywasconducted in cerrado vegeta- social wasps on many insects (Gobbi et al. 1984, tion during a five week survey (August, October Gobbi and Machado 1985, Machado et al. 1987, throughDecember 1988 andJune 1989) at theRio Raw 1988)confersonthema fundamental impor- Manso Hydroelectric Power Station (HPS-Rio tance as biological control agents. Nonetheless, Manso) (14°52' S and 55°50' W), in the Chapada the study of thenests ofthese insectshas focused dos Guimaraes county, southern Mato Grosso mainlyon theirarchitecture (Jeanne 1975, Kojima State in central Brazil. 1982)andonthenumbersofindividualspercolony Cerrado sensu-lato is a semideciduous (Richards 1978), with few reports on pairsofspe- xeromorphicvegetation dominantinCentralBra- cies nesting close together (Windsor 1972, Starr zil, occupying about 20% of the wholecountry. It 1988). occurs in various structures from closed forest- Information on preferences for nest habitats likeforms topuregrasslands (Eiten 1972). "Habi- (Richards 1978, Reed and Vinson 1979, Forsyth tat" is used here to refer to a vegetation subtype 1980)andoncolonydensities(Rau1942,Kitayama within the cerradosensu-lato. etal. 1989) ofneotropical social wasps is still very The censuses of social wasp colonies (nests scarce. IncentralBrazil, 130speciesofwaspshave with resident adults) were conducted in campo been collected (Richards 1978, Raw pers. comm. umido, vereda, campo sujo, cerradosensu-stricto, and our own collections), but studies on their galleryforestand surroundingdirtroads.Charac- ecology are very fragmentary. terizingthesehabitatsverybriefly itcouldbesaid The aim of this report is to add new informa- that campo umido is a wet grassland without tion on colony densities and preference for nest visible woody plants (Fig. 1); vereda is a broad habitatsofsocialwaspsinthecerradosensu-latoof marshy valleybottomgrassland with buriti palm Central Brazil. (Mauritiavinifera)galleries(Fig. 2);camposujoisa cerrado grassland with a few, very scattered, low conspicuousshrubsoracaulescentpalms (Fig. 3); 134 Journalof Hymenoptera Research AiiP*:' =*#;*> a--S^^Ss M K? 1 Fig. 1. Area of 100nvofcampoumidowherewasp nestsweresurveyed. Fig. 2. AreaofVereda (Photoby Dr. RobertoCavalcante) 135 v^g»HK 1 Fig. 3. Areaofcamposujo. Fig.4. Areaofcerradosensu-stricto (PhotobyDr. RobertoCavalcante). 136 Journalof Hymenoptera Research '4MB£^4 < Fig. 5. Areaofgallery forest (PhotobyDr. RobertoCavalcante). cerradosensu-strictoincludes formswiththe total 1972),galleryforestanddryforest (deciduousand woody plant cover of about 30-40% and with a semi deciduous mesophytic forest, Eiten 1972). canopy generally less than seven meters (Fig. 4) Forthestudyoncolonydensity,knownareas m and gallery forest is usually a narrow evergreen were sampled, in gallery formest (7500 2) and in mesophytic forest following the streams (Fig. 5) cerrado sensu-stricto (10000 2). Nests were lo- (Eiten 1972). catedamongleaves,onbranches,onthetrunksof Searches for nests were conducted in four treesandinholesintree-trunksandintheground. different months, covering two seasons: dry sea- Binocularswereusedtolocatenestsinthecanopy. m son (June and August) and wet season (October In addition, five squares of 100 2 each were and December) in six habitats. Each habitat re- surveyed incampo timido, where nests ofwasps ceivedthesameintensityofsearchingduringeach were sought among tufts of grasses and sedges ofthese seasons. (Fig.l). Fromeachnest,adultwaspswerecollectedto The survey for estimates of the density of guarantee identification of the species. All the colonies, within the study area, was done during nests and insects sampled are deposited in the thewetseason.Threepeoplespentapproximately Laboratorio de Zoologia, Departamento de 360 hours searching for nests. In each habitat the Zoologia in the Universidade de Brasilia. time spent per square meter was about one per- ThedataonXavantinaandSerradoCachimbo son-minute. (10°50'S and 51°47'W), in northern Mato Grosso For the estimates of density of adult wasps/ state were compiled from Professor Richards' ha, thenumberofadultswithinsomeofthenests (1978) species descriptions of nest habitats using were counted and also, for some species, data only the data where there was no doubt on the from Richards (1978) were compiled. location of the nests). Richards' censuses were In each table the habitats, when it was pos- conductedincamposujo,dirtroadsandclearings, sible, were arranged in order of increasing com- cerrado sensu-stricto, Cerradao (the medium tall plexityofstructurebecausethismakes iteasierto arboreal form of cerrado with a closed or semi- see general patterns in species preferences for opencanopywith30-40% treecrowncover, Eiten habitats. Volume 3. 1994 137 RESULTS AND DISCUSSION seven in four and three in five habitats (Table 3). Theareasurveyedwasdifferentineachhabitat so 1. Nesting Habitat Preference ofWasps thenumberofcoloniesfounddonotrepresentone absolute abundance but the relative habitat pref- A total of 100colonies, comprising30species erence fornesting. in 15 genera of wasps were encountered in six Of the total number of colonies recorded by differenthabitatsinChapadadosGuimaraes(Table Richards and us from Mato Grosso, the species 1). Among them, 18 species nested in only one with the largest number of colonies was Polybia habitat,nineintwo—,andthree(Polybia(Myrapetra) ruficeps(14%),followedbyPolybiaoccidentalis(9%), ruficepsSchrottky averycommonspeciesofthe Polybiajurinei(6%),Polybia(Myrapetra)erythrothorax region, Chartergus chartarius (Olivier) and Richards(5%),Polybiaignobilis(5%),Paraclmrtergus Clwrtegelhis communis Richards) in three habitats fratemus (Gribodo) (4%) and Epipona tatua (4%). (Table 1). Of the species that nested in only one The genus Polybia represents 60% of the colonies habitat, most were found in cerrado sensu-stricto reported from the two regions of Mato Grosso (sevenspecies), ingalleryforest (fivespecies)and State(Table3),rangingfrom67%inXavantinaand incampoumido(fourspecies) (Table 1).Ofthe30 Serra doCachimbo (Table2) to45% in RioManso species collected in this study, only Polistes (Table 1). Amongallthecoloniesofthe 19species (Epicnemius) pacificus liliaciosus de Saussure was of Polybia collected, 58% were found in cerrado not collected by Richards (Table 1 and 2). This sensu-stricto (Table 3) ranging from 31% in Rio subspecies has been collected only rarely in cen- Manso and 55% in Xavantina and Serra do tral Brazil and, until Richards' 1978 record, its Cachimbo (Tables 1 and 2). distribution was thought tobe restricted in Brazil Richards (1978) suggested that the choice of totheNorth(Amazonas,Amapaand Parastates). habitat for nesting is very characteristic and less Polybiaruficepswasthecommonestspeciesofwasp diversethanthatused forforaging. Hisopinionis atRio-Mansowith23colonies,ofwhich70%were confirmed in our survey at Rio Manso. For ex- foundincerradosensu-stricto.Threeotherspecies, ample, both Synoeca suririama (L), which nests in Epipona tatua (Cuvier), Synoeca surinama (L) and gallery forest, and Polybia (Trichothorax) sericea Oiartergus chartarius, with eight colonies each, (Olivier) in cerrado sensu-stricto, were collected were also common (Table 1). when theyhunted ingallery forest,cerradosensu- Richards (1978) recorded 199 colonies com- stricto, campo sujo and campo umido. Of the 30 prising51 speciesin 14generanesting insixhabi- species of wasps at Rio Manso, 21 (70%) were tats (Table2). Most ofthespecieshecollected (25 encountered foraginginmorethanonehabitat(in of the51), were found nesting only in one habitat preparation). (eight of them in dry forest), 12 species nested in Awatersource isimportantforwaspstonest two habitats, eight nested in three habitats, three successfully, (Rau 1942, Forsyth 1980). The latter nestedinfour,andonespeciesPolybia(Myrapetra) authorconcluded that the greatercolony density platycephala Richards nested in five habitats. In of wasps in gallery forest was due mainly to the Xavantina and Serra do Cachimbo, Polybia presence of water. Wet habitats at Rio Manso (Myrapetra) occidentalis (Olivier) with 24 colonies (galleryforest,eight/haandcampoumido60/ha) (12%),wasthemostabundant,followedbyPolybia also had higher colony densities than did dry ruficeps (10%), Polybia (Apopolybia) jurinei de habitats (cerrado sensu-stricto five/ha). Polistes Saussure (8%), Polybia (Trichothorax) ignobilis (Epicnemius) subsericeus de Saussure and (Haliday) (7%) and Polybia (Formicicola) rejecta (F) Mischocyttarus (Mischocyttarus) drewseni de (5%) (Table 2). Saussure which nest in campo umido, had higher ThedatacollectedbyusandbyRichardswere colonydensitycompared tootherspecies in drier combinedandforthesametypeofhabitatthedata habitats,suchascerradosensu-stricto.Availability were lumped (Table 3 representing the sum of ofwaterallyearroundandnestprotectionbytufts Tables 1 and 2). At the nine habitats 299colonies, of grasses and sedges, could be the cause of that comprising 61 species and 16 genera, were col- high density. lected. Twentyeightspecies (46%)nested inonly Most animals have preferences forparticular one habitat, 13 species nested in two, 10 in three, habitats (Partridge, 1978). In Mato Grosso ap- 138 Journalof Hymenoptera Research Table 1. Wasps nesting habitats in Rio Manso Chapada dos Guimaraes: Mato Grosso, Brazil. Species Volume 3, 1994 139 Table 2. Wasp nesting habitats of Xavantina and Serra do Cachimbo: Mato Grosso, Brazil (Data from Richards, 1978) Species 140 Journalof Hymenoptera Research CS DC CE CD GF DF TT Species Stelopolybia angulata Volume 3. 1994 141 CU VE CS OF DC CE CD GF DF TT Species Polistes cinerascens 142 Journalof Hymenoptera Research Table4. WaspcoloniesdensityinthreedifferenthabitatsinRioManso-Chapadados Guimaraes: MatoGrosso, Brazil. Campo Cerrado Gallery umido sensu stricto forest Area (m2 )