ARTICLE What do we know about Neotropical trap‑nesting bees? Synopsis about their nest biology and taxonomy Camila Cristina Ferreira da Costa¹² & Rodrigo Barbosa Gonçalves¹³ ¹ Universidade Federal do Paraná (UFPR), Departamento de Zoologia (DZOO). Curitiba, PR, Brasil. ² ORCID: http://orcid.org/0000-0003-1950-7525. E-mail: [email protected] (corresponding author) ³ ORCID: http://orcid.org/0000-0001-5623-0938. E-mail: [email protected] Abstract. Cavity-nesting bees are enigmatic because they are difficult to observe in the wild, hence trap-nests (man-made cavities) provide the means by which these bees may be studied. Trap-nests is an efficient methodology to study these bees and are common worldwide. These traps have been used for a variety of reasons, including inventories, to examine pollen load, to study habitat disturbance, and bee conservation. However Neotropical trap-nesting bees’ taxonomy and biology are still poorly known and here we provide a review about these subjects. We searched for trap-nest bee studies in the Neotropical Region using Google Scholar and ISI Web of Science at any time in the past to December 2017. We found 109 independent stud- ies, most of which were from Brazil (87 studies), followed by Argentina (10 studies), and other countries had fewer than five studies each. A total of 140 species, 24 genera, 10 tribes and three subfamilies were reported in trap-nests. Nest architecture was described for only 49 species. Taxonomy is only well-known for 14 genera, somewhat known for seven and is essentially unavailable for three genera. Construction material, closing plug and cell shape are similar among species in the same tribes and genera. Vestibular and intercalary cells, and the preliminary plug are variable, even at the specific level. Apinae is the most studied group with available data for all genera recorded in trap-nests. Colletinae is the least-studied group and nothing is known for their nesting biology. Megachilinae is intermediate, with some studies of taxonomy and nesting. We suggest that further trap-nest studies should provide more detailed information on nest architecture and construction materials, including explicit mention of structures that are absent. All Neotropical bees need more taxonomic studies, but some, such as Hylaeus and Megachile, require more attention since Hylaeus is essentially unknown and Megachile is very common on trap-nests. Key-Words. Bee hotels; Diversity; Methodology; Nesting behavior; Systematics. INTRODUCTION ples of natural substrates include snail shells (Gess & Gess, 2008), rock surfaces (Eickwort, 1975) and Bee nests ordinarily comprises brood cells and man-made cavities, such as in brick walls (Santos associated structures and are often in burrows in et al., 2016), metal frames (Sheffield et al., 2011), the soil, aboveground cavities or free-standing farm tractor radiators (Sheffield, 2017) and door (Michener, 2007). Most bees and apoid wasps ex- locks (RBG pers. obs.). cavate underground nests and this form of nest- As a consequence of the wide variety of nest- ing is primitive in the superfamily (Melo, 1999; ing substrates, artificial nesting substrates (trap- Hedtke et al., 2013; Branstetter et al., 2017). While nests, nest-boxes, bee hotels) can be used to trap we do not yet have a phylogenetic reconstruction these cavity nesting bees and wasps (Krombein, of substrate preference for all bee species, appar- 1967; MacIvor & Packer, 2015). These traps are ently aboveground nesting arose independently often made of bundles of hollow stems, paper several times. Four of the seven bee main lineag- or cardboard tubes (Camillo et al., 1995; Araújo es have species that nest in cavities and there are et al., 2016) and holes drilled in wood (Krombein, some reversals to soil nesting (Almeida, 2008). 1967; Buschini, 2006; see MacIvor, 2017 for a re- Aboveground substrates are variable and cav- view). Characteristics of the entrance diameter, ity-nesting bees are likely to be an artificial eco- nest length, color and also placement of nests logical grouping. The use of existing tunnels in all influence bee selection and use of traps-nest deadwood is common and bees often excavate (Krombein, 1967; MacIvor & Packer, 2015). Also, decomposing wood and soft pith in stems and traps can be placed in aggregates of greater den- galls for nests (Sheffield et al., 2011). Other exam- sity to improve the likelihood of use. Studies tend Pap. Avulsos Zool., 2019; v.59: e20195926 ISSN On-Line: 1807-0205 http://doi.org/10.11606/1807-0205/2019.59.26 ISSN Printed: 0031-1049 http://www.revistas.usp.br/paz ISNI: 0000-0004-0384-1825 http://www.scielo.br/paz Edited by: Kelli dos Santos Ramos Received: 29/08/2018 Accepted: 15/04/2019 Published: 15/05/2019 Pap. Avulsos Zool., 2019; v.59: e20195926 Costa, C.C.F. & Gonçalves, R.B.: Neotropical trap-nesting bees 2/16 to develop their own type of trap and so a wide variety Table 1. A summary of trap-nesting bee genera from the Neotropical region. of traps and their dispositions have been used, making Notes: ¹morphospecies are excluded for most genera; ²only recorded as mor- comparisons of these studies very difficult. phospecies; ³available for nest description of at least one species; ⁴sufficient As a consequence of the successful use of traps, for taxa with published taxonomical revision, moderate for taxa only identi- studies are common worldwide, with over 1,300 results fied by taxonomists, insufficient when no revision is available. in Google (January 2018). Traps are used for many rea- Number of recorded Trap-nest Taxonomic sons, including to sample and monitor cavity nesting Taxon species and their predators (Araujo et al., 2017; Oliveira & species¹ description³ knowledge⁴ Apinae Gonçalves, 2017), to compare habitats among different Centridini regions (Araújo et al., 2016), to examine altitudinal gradi- Centris 14 Available Moderate ents (Perillo et al., 2017) and vertical stratification (Morato, Euglossini 2001b; Stangler et al., 2015, 2016), to detect responses Eufriesea 8 Available Sufficient to fragmentation (Stangler et al., 2015, 2016; Rocha- Euglossa 14 Available Moderate Filho et al., 2017) and urbanization (Pereira-Peixoto et al., Tetrapediini 2014), to promote pollination and pollinator conserva- Tetrapedia 7 Available Insufficient tion (MacIvor & Packer, 2015) and to study the nest bi- Xylocopini ology and behavior of particular groups (Rocha-Filho & Xylocopa 6 Available Moderate Garófalo, 2016a,b; Moure-Oliveira et al., 2017). Colletinae Despite of the large number of trap-nest studies, the Colletini Neotropical bee fauna taxonomy and diversity is still Colletes 1 Unavailable Insufficient poorly known (Silveira et al., 2002). Here we summarize Rhynchocolletes 1² Available Sufficient the available information on biology and taxonomy of Hylaeini trap-nesting bees in this region. A synopsis is important Hylaeus 1 Unavailable Insufficient to provide direction for future studies because further Megachilinae coordinated efforts will be important to produce com- Anthidiini parable data and robust advances in this research field. Anthidium 4 Available Sufficient Anthidulum 1² Unavailable Sufficient Anthodioctes 5 Available Sufficient MATERIAL AND METHODS Carloticola 1 Available Sufficient Ctenanthidium 1 Available Sufficient To summarize the trap-nesting studies, we searched Dicranthidium 3 Unavailable Sufficient using Google Scholar and ISI Web of Science through the Duckeanthidium 1 Available Moderate end of 2017. We used the following search terms: (Ninhos Epanthidium 5 Available Sufficient armadilha OR Nidos trampa OR Trap-nest OR Trap-nest Hypanthidium 1 Unavailable Moderate bees) AND (Neotropical OR countries names). We includ- Loyolanthidium 1² Unavailable Moderate ed all countries from Chile to Mexico as search terms. The Nananthidium 1 Unavailable Sufficient literature cited along any retrieved study was also used Saranthidium 2 Unavailable Sufficient to find additional references. The following criteria was Lithurgini used to select the studies for this work: (1) used trap-nest- Microthurge 1 Unavailable Sufficient ing methods (understood here as any artificial cavity that Trichothurgus 1 Available Sufficient was built by the researcher in which bees nested); (2) a Megachilini primary reference, revision studies were not included; Megachile 33 Available Insufficient and (3) published in a peer reviewed journal or as an ac- Osmiini ademic thesis or dissertation (other gray literature such Heriades 1² Unavailable Moderate as abstracts and conference reports were not included). Data for nesting behavior, other biological details Melo & Gonçalves (2005). Identification at morphospe- at higher taxonomic levels and the number of species cies (“spp.”) was also included in Table S1 but not count- in the world follow Michener (2007). The number of ed in Table 1 except for the genera only recorded for Neotropical species follows the online version of Moure’s undetermined species. We opted to include all records Bee Catalogue (Moure et al., 2013). Nesting behaviors of of primary references except for a single morphospe- species and genera were gathered from the original stud- cies of Neofidelia (Veddeler et al., 2010). This refers to soil ies. Terminology for nest architecture follows Krombein nesting species that are probably incorrectly identified. (1967) as illustrated in Fig. 1. Trap-nest biology knowl- Taxonomy for each genus was evaluated at the species edge is considered “available” when there is at least one level