Original article Time of drone flight of Apis laboriosa Smith in Nepal BA Underwood Cornell University, Department of Entomology, Ithaca, NY 14853, USA (Received 21 March 1990; accepted 10 July 1990) Summary — Drones of Apis laboriosa were found to fly in the early afternoon between 12.20 h and 14.20 h in Nepal. These flights were not associated with either cleansing flights or orientation flights. Weather conditions during the observation period did not permit flight in the late afternoon or eve- ning. It is suggested that the time of drone flight may serve as an isolating mechanism between the closely related A laboriosa and A dorsata; however, additional data are required. Apis laboriose / Apis dorsata / drone flight / Nepal INTRODUCTION sympatric distribution of the 2 in Assam) could be the time of drone flight. A recent study of A laboriosa in Nepal provided an The taxonomic status of Apis laboriosa opportunity for some preliminary observa- Smith 1871 has been the subject of some tions to be made of the flight activity of discussion in recent years. After exami- Apis laboriosa drones. ning workers of A dorsata and A laboriosa, Sakagami et al (1980) concluded on the basis of morphological characters that MATERIALS AND METHODS they should be considered as separate Ruttner has stated that the species. (1988) Studies were carried out at a cliff site at an alti- differences noted et are by Sakagami al, tude of 2 680 m in the valley of the Modi Khola of a quantitative rather than qualitative na- river in Kaski District, West-Central Nepal. A ture and do not in themselves justify assi- viewing platform suspended from bolts an- gning a specific status to A laboriosa. All chored to the cliff face made it possible to ob- the commonly recognized species of Apis serve an A laboriosa colony at a distance of less than 1 m. The entire surface of the dorsata, florea, mellifera, and the colony (cerana, was visible and drones were easily distinguisha- recently "rediscovered" koschevnikovi) ex- ble from workers. Flight activity of the colony hibit striking differences in drone genitalia. was monitored from 09.30 to 18.30 h on 4 days the 1988. Drone Although no such differences have during period 2-10 September was the number of been noted in the genitalia of males of A flight assessed by counting drones on the surface of the colony dur- laboriosa and A and Un- arriving dorsata, McEvoy ing 10-min intervals. These counts were begun derwood (1988) argued for recognition of within about 1 min after the first drone was seen A laboriosa and suggested that a possible leaving the colony and ended after drone flight isolating mechanism (given the apparent was suspended (ie, no exits or arrivals for a full 10-min period). On the 14th September, the col- An orientation flight was observed at comb was cut and the bees were killed and ony 10.30 h on the 10th September, but no counted to determine the number of workers drones were seen in it. From and drones in the colony. taking part 12.00 to 12.10 h on that day, 609 workers were observed returning to the nest. Work- er continued unabated at the RESULTS flight activity time the first drone was seen departing at 12.27 h. The activity level was so high that At most times, only worker bees could be it proved impossible to monitor both worker seen on the surface of the protective cur- and drone flight simultaneously. Thus, at tain of the A laboriosa colony. On all 4 ob- the time of initiation of drone flight, there servation days, drones began to appear was no diminution in foraging activity, such on the surface of the curtain between as might occur prior to an orientation flight 12.15 and 13.00 h. Flight activity was seen (Lindauer, 1956); the flights observed were on only 2 days; inclement weather cur- probably mating flights. tailed drone at about 13.30 h on 1 flight Inspection of the colony on the 14th day and entirely prevented it on the other September revealed that although there 2 In and also days. addition, apparently were several thousand cells of capped because of the weather no conditions, worker brood, there were no eggs or drone worker was observed later than flight brood and only 2 unsealed larvae. Of a to- 15.30 h. tal colony population of 21 312 only 230 in- Flight by drones was not associated sects were drones. with either cleansing flights (no such flights took place within the observation period) or orientation flights (Lindauer, 1956). Alto- DISCUSSION gether, 357 arrivals of drones were ob- served, all between 12.20 and 14.20 h. Of The absence of eggs and unsealed brood 287 arrivals observed on the 10th Septem- is an indication that the ber, the only day when full flight occurred, probably colony was making preparations for a migratory 211 (74%) took place between 13.20 and move, normal behavior for A laboriosa col- 14.20 h 1; for convenience, observa- (fig onies at this altitude in tion have been combined into 20- September (Under- periods While the status of min intervals. wood, 1990). migratory a colony may influence the timing of orien- tation flights (Lindauer, 1956), there are no data to suggest that impending migration would affect the time of day at which drones take mating flights. Preferably, a comparison of the time of drone flight of A laboriosa and A dorsata should be made using data from the 2 spe- cies where they occur sympatrically, or at least in relatively close proximity. Unfortu- nately, data for the time of A dorsata drone flight in Nepal are unavailable (have in fact not been collected). It has been reported that Apis dorsata drones take mating flights between 18.15 h and 19.00 h in Sa- colonie d’Apis laboriosa qui nichait dans bah on the island of Borneo (Koeniger et une falaise à 2 680 m d’altitude dans le al, 1988), between 18.00 and 18.45 h in Centre-Ouest du Népal a été observée à Sri Lanka (Koeniger and Wijayagunaseke- une distance < 1 m. L’activité de vol de la ra, 1976), and in a 15-20-min period just colonie a été suivie pendant 4 j en sep- before dark in Mysore State, India (FC tembre 1988. Les couches externes du ri- Dyer, personal communication). deau protecteur de la colonie étaient habi- Indirect evidence that A dorsata drones tuellement uniquement constituées d’ouvrières lors de chacun des in Nepal may follow this pattern of flying at mais, jours les mâles ont commencé à dusk was suggested by observations of d’observation, worker flight in Rampur, Chitwan District. faire leur apparition à la surface entre 12 h 15 et 13 h 00. Le vol des observé In March 1984, a time when drones were mâles, known to be present (from samples of the sur 2 j seulement, se limitait à la période populations of the colonies under observa- 12 h 20-14 h 20. Les conditions météoro- n’ont le vol des mâles tion), 2 A dorsata colonies were observed logiques pas permis en fin ni dans la soirée. Les at close range (< 2 m) on successive days d’après-midi between 08.30 and 16.30 h. Although vols des mâles n’étaient associés ni à des vols de ni à des vols d’orienta- workers were foraging actively, no drone propreté, tion. Sur les 287 arrivées observées le 10 flights occurred; indeed, no drones ap- seul où les vols se sont peared on the curtain surfaces of these septembre, jour colonies (personal observations). pleinement déroulés, 211 (74%) ont eu lieu entre 13 h 20 et 14 h 20 Les mâles If drones of A dorsata colonies (fig 1). nesting d’Apis dorsata volent le soir (juste avant le in the Himalayan foothills also fly at dusk, coucher du soleil) à Bornéo (Koeniger et the data for A laboriosa suggest that the al, 1988), au Sri Lanka (Koeniger et Wi- time of drone serve as a flight may repro- jayagunasekera, 1976) et dans l’Etat de ductive isolating mechanism between the Mysore en Inde (FC Dyer, communication two species. Evidence presented here personnelle). Si c’est aussi le cas pour le must be regarded as preliminary, however; Népal, les observations présentées ici sug- there is an evident need for additional la de vol des mâles data. In it must be established gèrent que période particular, servir de mécanisme d’isolement that A laboriosa drones do not at peut fly dusk, entre les dorsata et A laboriosa even under favorable weather conditions. espèces A étroitement apparentées. Mais il est néces- saire de rassembler des données complé- mentaires. ACKNOWLEDGMENTS cerana / laboriosa / vol des The author thanks His Majesty’s Government for Apis Apis permission to travel and conduct research in Ne- mâles / Nepal pal. Financial support was provided by a grant (No 3682-87) from the National Geographic So- ciety. Zusammenfassung — Drohnenflug- Discussions with FC Dyer, RA Morse, and zeiten von laboriosa Smith in TD assisted the author in Apis Seeley improving Ein Volk von das an the Nepal. Apis laboriosa, upon original manuscript. einer Felswand im westlichen Zentral- Nepal in einer Seehöhe von 2680 m nis- Résumé — Période de vol des mâles tete, wurde aus einer Entfernung von weni- d’Apis laboriosa Smith au Népal. Une ger als 1 m beobachtet. Die Flugtätigkeit des Volkes wurde vier Tagelang im Sep- Apis cerana / Apis laboriosa / Drohnen- tember 1988 beobachtet.