A nesting aggregation of Megachile (Creightonella) atrata Smith in the Philippines comprised almost 300 active nests.  The bees in rapid flight resemble the hornet Vespa tropica Linnaeus. The nest structure is similar to that reported for M. (C.) frontalis (Fabricius) in New Guinea

Starr, Christopher K.

English

The University of Kansas: Journals@KU

Journal of MelittologyBee Biology, Ecology, Evolution, & Systematics The latest buzz in bee biologyNo. 68, pp. 1–5 20 April 2017Copyright © C.K. Starr. Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International (CC BY-NC-ND 4.0).ISSN 2325-4467A nesting aggregation of the solitary bee Megachile atrata (Hymenoptera: Megachilidae) in the PhilippinesChristopher K. Starr1Abstract.  A nesting aggregation of Megachile (Creightonella) atrata Smith in the Philippines com-prised almost 300 active nests.  The bees in rapid flight resemble the hornet Vespa tropica Linnae-us. The nest structure is similar to that reported for M. (C.) frontalis (Fabricius) in New Guinea.1 Department of Life Sciences, University of the West Indies, St. Augustine, Trinidad & Tobago (ckstarr@gmail.com).doi: http://dx.doi.org/10.17161/jom.v0i68.6467Megachile (Creightonella) atrata F. Smith is a large, black leafcutter bee described from the Philippines (Smith, 1853: 182).  It closely resembles and may be conspecific with M. (C.) frontalis (Fabricius); the two have a summed range from the Malay Penin-sula and Sumatra to the Philippines and the Solomon Islands (Michener & Szent-Iva-ny, 1960; Michener, 2007).  The published nesting biology of South Asian Creightonella Cockerell is largely limited to a single paper on M. frontalis in New Guinea (Michener & Szent-Ivany, 1960).  Beyond that, these widespread and locally abundant bees are known to visit many species of flowering plants and may be valuable as pollinators of some crops (Cervancia & Bergonia, 1991; Klein et al., 2003; Wilmer & Stone, 1989).Michener & Szent-Ivany (1960) report that M. frontalis nests by burrowing in hard, clayey soil, often in large numbers.  Burrows are mostly 14–16 mm in diameter and 4–15 cm in length.  Longer burrows are often branched.  Nest cells are formed of separate layers of mud, masticated leaf pulp, and round leaf fragments (Michener & Szent-Iva-ny, 1960: their fig. IV; redrawn as fig. 41 in Iwata, 1976).  My purpose here is to report on a dense nesting aggregation of M. atrata in the Philippines, with notes on nest structure.All observations are from outside the village of Matuod (13°59’N 120°38’E), on Talim Bay in Batangas province, Philippines during September 1986 (mid-rainy sea-son).  The study site was an eroded low gulch surrounded by a mostly flat area, the whole with sparse low vegetation.  I thoroughly examined the gulch and marked the location of each open nest burrow, followed by a wider, less thorough search.  I exca-BRIEF COMMUNICATIONJournal of Melittology2 No. 68vated 30 nests, with an effort to collect their adults.Specimens in the National Museum of Natural History (Washington) collected by C.K. Starr in Batangas Province, Philippines and identified by S.W.T. Batra as M. atrata will serve as vouchers.My observations began when two local men offered to show me the site of a “hil-ulumbo-lupa” (soil hornet) colony in disused farmland.  This is the specific local name for the hornet Vespa tropica (Linnaeus), which usually nests underground (Matsuura, 1984; Matsuura & Yamane, 1990) and is common in farmland in much of the Philip-pines.  In my experience, it can be quite defensive and delivers a very painful sting. In fact, what my friends had found was a nesting aggregation of M. atrata.  The two species are of similar size, stoutness, and coloration, and both fly busily about their nesting sites, so that it is not surprising that they should mistake the bee for the hornet at a distance and should not approach close enough to realize the mistake.Standing in the aggregation, I waved my net about on three occasions.  Each time, a large mass of bees responded by flying close around me.  Walking about five meters away, I was followed by several bees, which continued to fly around me in a manner similar to that of hornets.  Twenty-two netted bees were all females.No bees stung me voluntarily.  On three occasions I induced a sting by holding a bee against my forearm.  Each was a sharply painful medium 2 on the standard pain scale (Schmidt, 1990: 387–419; Starr, 1985), very localized and faded within minutes.A search revealed 283 apparently active nests in an area estimated at 322 m2.  The core of the aggregation was 67 nests in an area of about 17 m2 at the foot of a low verti-cal earth bank (Fig. 1).  Nests outside this area were much more scattered.  Within the Figure 1.  Part of a low gulch in a field near Matuod, Batangas, Philippines.  The core of a Mega-chile (Creightonella) atrata Smith nesting aggregation is at the foot of one of the banks (middle ground), where the positions of 67 nests are marked with bamboo stakes.  These protrude on average about 15 cm above the ground.  There is only one nest on the ledge above, two on the steep bank face, and none in the relatively bare foreground.Starr: Nesting Aggregation of Megachile atrata2017 3core area, some burrow entrances were separated from nearest neighbors by no more than 2 cm.Some parameters of nest structure are shown in Table 1.  Nest burrows were most-ly 9–11 mm in diameter, smaller than recorded from M. frontalis.  The 22 nests with at Table 1.  Parameters of 30 Megachile (Creightonella) atrata Smith nests in a dense aggregation in Batangas province, Philippines.  Nests are arranged in sequence of approximate presumed age. Angle = initial angle of descent of the burrow, estimated by sight to the nearest 15°.  Length = length of the main burrow estimated to the nearest centimeter, followed by lengths of any side burrows.  Where a burrow has n completed cells and another cell begun, the number is given as n+.  Wing wear = fraying of the main female’s forewings, where known: 0 = no visible fraying, 1 = slight fraying at the tips, 2 = moderate fraying extending into one or more wing cells.Nest. No. Angle Length (cm) No. of cells Wing wear1 60° 4 0 02 60° 4 0 03 45° 5 0 04 75° 5 0 05 60° 5 0 16 45° 8 0 07 90° 6 0 18 60° 7 0+ —9 60° 9 0+ —10 90° 12 0 111 90° 11 0+ 112 90° 5 1 113 75° 11 1 —14 45° 6 2 015 75° 11 2+ 016 60° 8 3 017 60° 7 2 118 75° 9 2 119 45° 13 2 —20 60° 16 2 121 60° 11 3 122 60° 11 3 123 60° 10 1 224 75° 7+3 3 125 75° 10 2 226 75° 16 2 227 75° 6+2+2+2 3 —28 90° 15+3 4 —29 90° 10+5+5 4 130 75° 9+4+4+4+2 7 1Journal of Melittology4 No. 68least the first cell started had lengths of 5–16 cm, very close to the range recorded from M. frontalis.  Some descended approximately vertically, but most were at an angle. Most burrows were more or less straight throughout, while some curved downward. Five of the 30 nests had a total of a total of 11 side-branches, each with 1–3 cells.  Most of these were close to horizontal, although two descended at about 60° from the hori-zontal.  Cells at the end of a main burrow or a side branch kept the burrow/branch orientation.The maximum number of cells recorded from a nest was seven.  Twenty finished cells had a mean length of 22.7 mm, shorter than those recorded from M. frontalis. However, their composition and structure showed no evident differences from those of M. frontalis.  The few cells that I opened had closures of chewed leaf pulp sand-wiched between 1–4 layers of intact leaf.  As in M. frontalis, the leaf disks forming the outer cell wall were coarsely irregular in shape.  The mass of cell provisions was in the opposite end of the cell, with the egg placed on top of it, as in M. frontalis. Four of 25 nests examined after dark had closed burrows, of which two had the appearance of temporary closures.  No bee was at the entrance of open burrows, and probing several of them with grass leaves produced no indication of bees inside.The relationship between nest size and female wing wear (Table 1) was only weak-ly positive (Spearman’s rank correlation test, p≈0.10).  This is an odd result, although at least four nests with no completed cells had females with some wing-wear, suggesting that it was not their first attempt at nesting. Iwata (1976: ch. 13) characterized the habit of digging their own nest burrows as unusual among megachilids, although this appears not to be the case in all parts of the world (Eickwort et al., 1981).  This leaves open the question why females nest so close to each other.  Giovanetti et al. (2006) reviewed possible advantages to aggregated nesting in Hymenoptera, dividing these into abiotic and biotic factors.  Among the for-mer, a scarcity of suitable nest sites is almost certainly not a factor in M. atrata, at least in the study area.  The most commonly cited biotic factor is parasite pressure.  As an example, Larsson (1986) inferred this as a key factor in the solitary soil-nesting wasp Bembix rostrata (Linnaeus), suggesting not collective active defense but a selfish-herd effect.  The introduced fire ant Solenopsis geminata (Fabricius) is abundant in the study area and could certainly pose a threat to brood and provisions, although it is doubtable that aggregated nesting can provide any protection against these much smaller insects.My working hypothesis is that the resemblance to V. tropica of a mass of flying M. atrata provides protection against vertebrate brood predators through intimidation, a possibility not treated by Giovanetti et al. (2006).  The shrew rat Chrotomys mindorensis Kellogg is a likely candidate.  This diurnal, semi-fossorial rodent is fairly common in the lowlands of Luzon, where it feeds on soft-bodied soil invertebrates (Heaney, 2010, & pers. comm.).  The civets Paradoxurus hermaphroditus (Pallas) and Viverra tangalunga Gray may also prey on bee brood if the soil is not very hard (L.R. Heaney, pers. comm.).ACKNOWLEDGEMENTSThanks to De La Salle University, Manila, for use of its marine field station during this study, S. Animaw and E. Reyna for showing me the nesting aggregation, S.W.T. Batra for iden-tifying M. atrata, J. Thomas for a key bibliographic assist, and C.D. Michener, C. Praz, and V.H. Gonzalez for critical comment.Starr: Nesting Aggregation of Megachile atrata2017 5REFERENCESCervancia, C.R., & E.A. Bergonia. 1991. Insect pollination of cucumber (Cucumis sativus L.) in the Philippines. Acta Horticulturae 288: 278–282.Eickwort, G.C., R.W. Matthews, & J. Carpenter. 1981. Observations on the nesting behavior of Megachile rubi and M. texana with a discussion of the significance of soil nesting in the evolu-tion of the megachilid bees (Hymenoptera: Megachilidae). Journal of the Kansas Entomologi-cal Society 54(3): 557–570.Giovanetti, M., J.D. Asís, & J. Tormos. 2006. Living in aggregations: Theories and facts in the life of Hymenoptera. Marie Curie Fellowship Association Abstracts 4: 1–5.Heaney, L.R. 2010. Synopsis of Philippine mammals. [http://archive.fieldmuseum.org/philip-pine_mammals/; last accessed 1 December 2016].Iwata, K. 1976. Evolution of Instinct: Comparative Ethology of Hymenoptera. Amerind Publishing Co.; New Delhi, India; 535 pp.Klein, A.-M., I. Steffan-Dewenter, & T. Tscharntke. 2003. Pollination of Coffea canephora in relation to local and regional agroforestry management. Journal of Applied Ecology 40(5): 837–845.Larsson, F.K. 1986. Increased nest density of the digger wasp Bembix rostrata as a response to parasites and predators (Hymenoptera: Sphecidae). Entomologia Generalis 12(1): 71–75.Matsuura, M. 1984. Comparative biology of the five Japanese species of the genus Vespa (Hyme-noptera, Vespidae). Bulletin of the Faculty of Agriculture, Mie University 69: 1–131.Matsuura, M., & S. Yamane. 1990. Biology of the Vespine Wasps. Springer; Berlin, Germany; xix+323 pp.Michener, C.D. 2007. The Bees of the World [2nd Edition]. Johns Hopkins University Press; Balti-more, MD; xvi+[i]+953 pp., +20 pls.Michener, C.D., & J.J.H. Szent-Ivany. 1960. Observations of the biology of a leaf-cutter bee Mega-chile frontalis, in New Guinea. Papua and New Guinea Agricultural Journal 13(1): 22–35.Schmidt, J.O. 1990. Hymenopteran venoms: Striving toward the ultimate defense against ver-tebrates. In: Evans, D.L., & J.O. Schmidt (Eds.), Insect Defenses: Adaptive Mechanisms and Strategies of Prey and Predators: 387–419. State University of New York Press; Albany, NY; xv+482 pp.Smith, F. 1853. Catalogue of Hymenopterous Insects in the Collection of the British Museum. Part 1. Andrenidae and Apidae. British Museum; London, UK; [iii]+197 pp., +6 pls.Starr, C.K. 1985. A simple pain scale for field comparison of hymenopteran stings. Journal of Entomological Science 20(2): 225–232.Wilmer, P.G., & G.N. Stone. 1989. Incidence of entomophilous pollination of lowland coffee (Cof-fea canephora); the role of leafcutter bees in Papua New Guinea. Entomologia Experimentalis et Applicata 50(2): 113–124.The Journal of Melittology is an international, open access journal that seeks to rapidly disseminate the results of research conducted on bees (Apoidea: Anthophila) in their broadest sense.  Our mission is to promote the understanding and conservation of wild and managed bees and to facilitate communication and collaboration among researchers and the public worldwide.  The Journal covers all aspects of bee research including but not limited to: anatomy, behavioral ecology, biodiversity, biogeography, chemical ecology, comparative morphology, conservation, cultural aspects, cytogenetics, ecology, ethnobiology, history, identification (keys), invasion ecology, management, melittopalynology, molecular ecology, neurobiology, occurrence data, paleontology, parasitism, phenology, phylogeny, physiology, pollination biology, sociobiology, systematics, and taxonomy.The Journal of Melittology was established at the University of Kansas through the efforts of Michael S. Engel, Victor H. Gonzalez, Ismael A. Hinojosa-Díaz, and Charles D. Michener in 2013 and each article is published as its own number, with issues appearing online as soon as they are ready.  Papers are composed using Microsoft Word® and Adobe InDesign® in Lawrence, Kansas, USA.A Journal of Bee Biology, Ecology, Evolution, & Systematicshttp://journals.ku.edu/melittologyISSN 2325-4467Journal of Melittology is registered in ZooBank (www.zoobank.org), and archived at the Univer-sity of Kansas and in Portico (www.portico.org).Editor-in-ChiefMichael S. EngelUniversity of KansasVictor H. GonzalezUniversity of KansasAssistant EditorsIsmael A. Hinojosa-DíazUniversidad Nacional Autónoma de México

A nesting aggregation of the solitary bee Megachile atrata (Hymenoptera: Megachilidae) in the Philippines

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A nesting aggregation of the solitary bee Megachile atrata (Hymenoptera: Megachilidae) in the Philippines

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