3.2.5. Introducing adult SHB into colonies
Ellis et al. (2003b) investigated the impacts of adult SHB on nests and flight activity of Cape and European subspecies of honey bees. They did this by adding SHBs to nucleus colonies nightly for 15 nights to simulate a large-scale, chronic invasion of SHBs into colonies. They developed the method outlined below for introducing adult SHBs into colonies daily.
- Rear adult SHBs according to the methods outlined in section 3.1.2.
- Prepare/equalize colonies prior to the experiments according to the methods outlined in the BEEBOOK paper on estimating colony strength (Delaplane et al., 2013).
- Collect adult SHBs from the rearing program with an aspirator (see Fig. 6).
- Place the exact number and sex (if needed see Fig. 9) of adult SHB intended for each colony into small vials before their release into the colonies. Adult SHB are much easier to release from a vial into a colony than by other methods.
- Colonies can be artificially-infested with SHB on any time schedule (daily, weekly, etc.) provided the introductions are done during evening hours. SHB adults preferentially invade colonies during evening hours (Neumann et al., 2012) so adults should be introduced during regionally-appropriate hours, between 1-2 hours before sunset and 1-2 hours after sunset. Ellis et al. (2003b) introduced SHBs between 17:00 – 21:00 h.
- To introduce SHB into the colony, lightly tap the vial
containing the beetles to cause the beetles to fall to the bottom of the vial.
SHB are quick crawlers and can easily escape the vial once the lid is removed if they are not tapped to the bottom of the vial first.
- Open the lid to the colony just enough to allow room to add the beetles.
- Add the adults to the uppermost super of the hive and close to the nest periphery to avoid overreaction by the host bees (“beetle shock”: bees being exposed to SHB abnormally and immediately removing the beetles from the hive). If the beetles are dumped into the centre of the bee cluster, the bees will attack the beetles immediately and many beetles may exit the colony within minutes of introduction. Beetles should not be anesthetized prior to introduction into the nest because anesthetized beetles are easily removed from colonies by adult bees.
- Replace the lid to the colony immediately after beetle
Modifications, additional uses, research on future improvements:
- The same method can be used to add adult SHB to full-size or nucleus colonies and to observation hives. Modifications can be made to the observation hive to accommodate SHB introduction since observation hive lids often cannot be removed (depending on hive design) (Fig. 14).
- Ellis et al. (2003b) added 100 SHB/night for 15 nights (totalling 1,500 SHB). Delaplane et al. (2010) added from 75 – 1,200 SHB/introduction every two months for a beetle threshold study. Consequently, the method is useful to simulate chronic, small scale beetle invasions or large, acute beetle invasions into the bee nest.
- For possible future improvement, one should investigate how SHB can be “control-released” into the nest over a longer period of time. The method outlined above involves the sudden addition of SHB adults to the nest, heightening the likelihood of “beetle shock”. Controlled introductions should be a point of future investigation.
- This procedure can be used to investigate SHB impacts on colony absconding behaviour, honey and pollen stores, amount of bees/brood in the nest, average colony flight activity, colony weight gain, SHB reproduction, SHB migration between colonies, etc. The beetles can be laboratory-reared, field-collected, all males, all females, age-cohort specific, etc. according to the needs of the experiment.
- Neumann and Härtel (2004) investigated the
removal of SHB larvae by honey bee colonies. They introduced larvae using
petri-dishes. Since SHB larvae are neither quick crawlers nor able to show the
turtle defence posture of adult SHB (Neumann et al., 2001c), worker bees
quickly remove them (Neumann and Härtel, 2004).
SHB have now well established populations in North America and Australia (Neumann and Ellis, 2008), and are likely to spread into more areas (Asia, South America, Europe) with potentially devastating effects on local managed honey bees and possibly other bees under suitable climatic conditions. This calls for concerted efforts of the community to better control this invasive species. However, despite this BEEBOOK paper there are still significant gaps in SHB methodology, thereby limiting its further spread and control. This calls for more research in this rather small field. Development of alternative treatments with natural enemies or an optimized trapping of adult / larval SHB in the field might constitute promising future avenues. On the other hand, this beetle has a truly fascinating biology and there is considerable potential to shed light on numerous fundamental questions in ecology and evolution. We therefore hope that this set of standard methods will attract more researchers to join the SHB research field, thereby stimulating exciting future research on this species.