Nidificação de Xylocopa spp. (Apidae, Xylocopini) em ninhos- armadilha em áreas de cerrado do Triângulo Mineiro

Abstract

Most species of Xylocopa construct their nests excavating dry wood, such as died branches and trunks, with its resistant jaws, or in bamboo colms. The present work aimed: (i) to compare two types of trap-nests (wood chunks from Spathodea campanulata and bamboo canes (Bambusa sp.)) in relation to the choice for nest construction by Xylocopa spp.; (ii) to verify the dynamics of nest foundation and development according to seasonality; and (iii) to provide information about number of trap-nest occupied and number of cells produced, nest longevity and natural enemies.The study was carried out in two areas of the Triangulo Mineiro s Cerrado, in the period of January of 2006 to December of 2007. Two types of trap-nests (NA) were used: branches of Spathodea campanulata (VS) and bamboo canes (GB) with one open end and the nodal septum closing the other one. NA, subdivided in seven categories ( A to G ), were conditioned in simple wooden coverings (ranches) for bee creation with 56 GB each, ranging from 1.01 cm to 2.40 cm and increasing in every two millimeter interval of cane opening diameter. Seven units of VS were subdivided in three categories, according to the following dimensions: bigger branches , smaller branches and trunks . Ranch monitoring was carried out biweekly to identify the foundation of new nests and observe active nests. In the two areas, a total of 88 nests were established by five species of Xylocopa. X. frontalis was the species that more often used the trap-nests (53.40%), followed by X. subcyanea (15.90%), X. suspecta (14.77%), X grisescens (11.36%), and finally, X. hirsutissima (4.54%). Difference in the ratio of use of trap-nests between species was not observed ( 2=0.845; p>0.005). The ratio of occupation of the two types of trap-nests in the different coverings was also not different ( 2=1.46; p>0.05). The VS of the category bigger branches (50 cm to 80 cm of length and 40 cm to 60 cm of circumference) was more frequently occupied. For the GB, the percentage of nest occupation was higher in categories E (1.81 cm to 2.00 cm) and F (2.01 cm to 2.20 cm). Of the total of nests originated in GB, 19 were reused continuously, while the others were abandoned by the nesting females. Abandoned nests could be occupied again (reuse after abandonment). The reuse after abandonment (n=32) was more abundant in the GB (n=26). In the VS there was a variation in the period of activity of 14 to 684 days (x=291.72±210.45). In GB, the nest activity ranged from nine to 357 days (x=92.59±86.56). The number of cells produced in the process of foundation and reactivation ranged from one to six and from one to five, respectively (x=2.12±1.47). There was no difference between the mean number of cells produced during the foundation and reuse of nests for X. frontalis. (ANOVA: F3.55=0.530; p=0.663). There was also no difference between the number of cells produced by each species during the process of foundation (ANOVA: F2.46=0,485; p=0.619). The number of nest building in the rainy season (GB=63.51%, n=48; VS=54.54%, n=24) was greater than in the dry season (GB=36.84%, n=28; VS=45.45%, n=20). The reuse after abandonment occurred only in the second year (2007), starting in February. Eleven adult individuals of cleptoparasites of Cissites maculata (Meloidadae) were collected next to the entrances of the host nests during the two years of observation. Besides the viability of nest management using GB, it was also shown in this study that trap-nests of Spathodea campanulata can be a good option for the attraction of Xylocopa spp.