Anthodioctes megachiloides Nesting in an Abandoned Nest of Brachymenes dyscherus (Hymenoptera: Megachilidae; Vespidae)

Abstract

Anthodioctes megachiloides Holmberg (Megachilinae: Anthidiini) is a solitary bee that uses pre-existing cavities in which to construct its nest, as it is true for many species in the family Megachilidae (Krombein, 1967; Bosch et al, 1993; Camillo et al, 1994). This bee species is commonly found in wood trap-nests that are offered artificially (Camillo et al, 1995; Alves dos Santos, 2003), like other species within the genus Anthodioctes (Morato, 2001; Camarotti-de-Lima and Martins, 2005). The nesting biology of A. megachiloides was studied from nests obtained from such traps in Sao Paulo (Alves dos Santos, 2004). The use of plant resin to coat the cells, construct the partitions and nest-closure is typical for this group of bees. Herein I document the opportunistic behavior of A. megachiloides using an abandoned nest constructed by a mud-daubing wasp and include some data on the nesting habits of this bee species. An old nest of Brachymenes dyscherus (Saussure) (Eumeninae, Vespidae) (B. dyscherus is the only species of Brachymenes known from Brazil and lowlands in the Neotropical region) made from mud was found on a tree trunk (about 20cm from the ground) at the Fazenda Sao Quirino, in Campinas, SP on 23 October 2002. The nest had some holes covered with resin, which is a typical nest entrance for some anthidiine species. The mud nest was observed for a while and then removed from the tree and transferred to the laboratory. During observation in the field no wasps were seen entering or leaving the nest, while two females of anthidiine bees were observed entering the open holes. Apparently the nest was abandoned by the wasps, and the bees were nesting in it, closing the wasps' emergence holes with resin. The mud nest was 93.7 mm in length and 53.7 mm in width, oval, flat ventrally and about 3.4 cm thick (Fig. 1 A-B) and made of light cream colored mud. The nest structure was similar to that described by Camillo (1999) for B. dyscherus, with parallel rows of brood chambers or cells. The mud nest was maintained at room temperature in the laboratory in a plastic box covered with fine and transparent net, awaiting emergence of the occupants. Emerged adults and nest were preserved dry and deposited in the Cepann Insect Reference Collection of the Institute of Bioscience at the University of Sao Paulo. A total of 1 5 wasp emergence holes were counted in the nest, three open and the remaining entrances sealed with resin. Curiously, one of the sides had 10 of the holes (Fig. 1C-D), while the other held 4 and one hole was in a ventral position. Thirty-six days after removal to the laboratory the first bees emerged. Between 27-29 November four males emerged in the cage. On 4 December another male emerged and also one female. Finally, on 5 December the last individual emerged and it was a female. Thus a total of seven adults of A. megachiloides emerged from the nest. According to the number of holes in the nest and the opened ones when it was found, probably a larger number of bees were living in the cells of the old B. dyscherus nest. A yellowish plant resin was used to coat the cells, construct the partitions and cell-closures, with a typical circle of this resin covering the entrance (Fig. 1E-F). This substance possibly has a protective function for the nest. According to Ghisalberti (1979), resin has a hydrophobic and antimicrobial potential and can also repel insects. The use of resin is widespread among Megachilinae such as Heriades Spinola, Chalicodoma Lepeletier and Anthodioctes Holmberg (Krombein, 1967; Muller et al, 1996; Michener, 2000; Morato, 2001). Sometimes the resin is mixed with soil grains or pieces of wood or stems. Besides the Megachilinae, other bees that typically use resin to construct the nest are Meliponini and Euglossini (Roubik, 1989; Garofalo et al, 1993). No parasites emerged from the nest, but from a previous study in this bee species possible enemies include Sapyga Latreille (Sapygidae), which is cleptoparasitic, and the parasitoid Melittobia Westwood (Eulophidae) (Alves-dos-Santos, 2003, 2004).