Newly recorded parasitic fly of honey bees in Sabah, Malaysia

Salim Tingek, Gudrun Koeniger, Nikolaus Koeniger

Keywords: Apis cerana, Apis dorsata, Apis koschevnikovi, Apis mellifera, Asia, bee parasite, Borneo, Conopid, Physocephala paralleliventris, thickhead flies

In a bee yard of the Agricultural Research Station Tenom in north-east Borneo, many colonies of the Asian hive bee Apis cerana were observed to have bees crawling on the ground underneath the hives. In some cases there were hundreds of dead bees nearby. We collected crawling and dead bees. By pressing the abdomen, two blackish stigma extruded from the sting chamber (Figure 1*).

Evidence of parasite

The dissected these bees and saw fly larvae and pupae. In the crawling bees, we found fly larvae with narrow anterior segments (proboscis) and at their end, stigma for breathing (Figure 2*). They almost filled the whole abdomen. The dead bees mostly contained fly pupae (Figure 3*).The position of their stigma was always in the sting chamber so the fly could obtain oxygen even within a dead bee. These fly larvae and pupae were typical ‘thickhead flies’ (Conopiaae).

We installed dead bee traps (which were Gary traps modified for Apis cerana) and monitored the colonies for at least four weeks. We collected more than 300 dead bees from each colony and again examined them using a Stereo microscope for fly larvae and pupae. From the 13 tested colonies, ail in different locations, 12 were infested. The infestation rate of the dead bees ranged from 10-90% of the colony. We could not yet evaluate the damage to the colony and the honey crop loss.

Adult fly

By this time we had not observed the adult insect. Therefore we placed some dead bees on humid soil in several jars. After about two weeks an It conopid fly (Figure 4*) hatched from the abdomen of the bee. Once familiar with the appearance of the conopid flies, we observed them feeding on nectar from flowers. Attacks on bees were seen only near hives, where the flies perched on nearby flowers or branches. From time to time they swooped down to bees at the hive entrance.

We observed these conopid flies also near Apis Koschevnikovi and Apis dorsata honey bee colonies and consequently collected and dissected crawling or dead bees of these species. These were found also to contain the fly larvae and pupae. The emerging flies were similar to the ones from Apis cerana.

We sent adult flies that emerged from Apis cerana to the NaturalHistory Museum London, UK for species determination. They were examined by Nigel Wyatt and identified as Physocephala paralleliventris Kréber. This species had been described in 1924 by a German biologist from northern Borneo. According to Wyatt there do not appear to be any published host records of this species. In general, conopids parasitise a wide range of stinging Hymenoptera (wasps and bees), but there are relatively few records from Apis species, and up to now these are invariably from Apis mellifera.

Discussion

If the parasitic flies can infest three Apis species this may indicate a great danger for Apis mellifera. In some parts of Borneo beekeeping is practiced with Apis mellifera, and if colonies are transported to other areas, it increases the possibility of transferring the parasite to other countries with a similar climate. We think it is important that beekeepers all over the world are made aware of this new record of a bee parasite. Further we recognised the parasitic fly only by collecting dead or crawling bees in the bee yard, but not by dissecting bees within the colony. The infection occurs when the fly deposits eggs on flying bees - probably foragers. Thus it may be difficult to recognise an infested bee within the hive. All beekeepers should carefully watch not only their colonies, but also their apiaries and bee yards for crawling or dead bees.

*Where reference to images or figures is made, please see original journal article

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