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Bees & Beekeeping: Present & Past

Small Hive Beetles at Their Worst in the Heat of the Summer

- February 1, 2018 - Wyatt A. Mangum - (excerpt)

In Virginia, the summer of 2017 was a difficult time for dealing with small hive beetles (hereafter just called beetles). I had heard others had trouble with beetles in newly made colonies (splits), something I had seen when I had bees in North Carolina years ago. While some of my apiaries had no extra problems with beetles, in a couple others I witnessed new behaviors, which I report here with photographs.

By late July 2017, beetle invasion pressure was intense in two apiaries. To demonstrate that invasion pressure on my strong frame-hive colonies with bee coverage at the entrance, I made a simple beetle-catching device. It was a short length of top bar cut from my top-bar hives with a saw groove cut in its side. A large nail in the top of the bar functioned as a convenient handle. I barely pushed the grooved side into the end of the hive entrance leaving just a little gap at the end of the entrance, a crack for the beetles to enter (see Figure 1). In summer heat and given local sun exposure of the hives, be careful about over-restricting air ventilation. (My research apiaries are in the shade.)

The bees could easily corral beetles in the side groove of the device. Those beetles could be entering the hive. Or they could have been in the hive, moving about, and the bees forced them to remain in the groove. I checked the groove in 24 hours or 48 hours, but I do not recommend leaving the device in the hive longer than that. This device is for short-term use only. Even then, it gives only a rough number of beetles that might be trying to enter the hive. If no beetles are in the groove, they still may have entered the hive without being stopped by the bees.

To check for beetles in the groove, I had an open clear plastic bag ready by the hive entrance. After gently removing the device (see Figure 2), I quickly put it in the plastic bag and closed it, even with some adhering bees. Shaking the bag and the device will help liberate the beetles from the groove. Cover a corner of the bag to give the beetles a dark spot to hide. This causes the beetles to settle down, and I can remove the trapping device and release the bees, who seek light, while the beetles hide in a dark corner. If needed, cooling the bag in an ice chest or refrigerator makes the beetles easier to count after spreading them out in the bag.

A similar situation, beetles hiding near a hive entrance, occurred at my bee house that holds numerous observation hives. Figure 3 shows the pipe entrance to one of my large multi-comb glass observation top-bar hives. See the crack in the exterior boards where they do not quite meet. After seeing beetles crowded in a saw crack from Figure 2, notice the crack in the boards by the entrance pipe. It is full of beetles. The beetles were mostly motionless, not soliciting food from bees. Even after I killed the beetles and cleaned out the crack, it refilled with beetles by the next night. I repeated the process for a few nights. Apparently, these were immigrating beetles taking refuge before trying to immigrate into the observation hive. This entrance pipe evidence and my simple device demonstrated beetle invasion pressure could be intense this past summer in two of my apiaries.

Now let’s look inside the hives, beginning with the single-comb observation hives in the bee house. In some summers leading up to the summer of 2017, adult beetles could be a problem with my single-comb hives. As reported earlier, adult beetles contaminated the pollen band, which apparently halted brood rearing. The rims of the cells seemed coated with a material, presumably accumulating there as the beetles repeatedly crawled in and out of the pollen cells (going over the cell rims). The colony, including the laying (physogastric) queen would cluster on the outside of the hive. After a few days, during which time the physogastric queen would become light enough to fly, the colony absconded. Remarkably only adult beetles caused the eviction and absconding of the bees–no beetle larvae were in these hives. (They appeared later after the bees absconded, leaving the hive undefended.)

At the end of July, I introduced two queens in a couple of single-comb observation hives. Dearth conditions existed at the time in my location. Both queens were accepted without difficulty. On their first brood cycles, both colonies experienced severe difficulties with adult beetles. The first colony (Colony #14) had sealed brood. At about 2:30 a.m. on August 12, I checked this colony and observed some strange behaviors. The brood nest bees were moving erratically, which prompted a closer examination. To my surprise, the bees were dragging older worker larvae (late instar larvae or propupae, which I’ll just call larvae) around in the brood nest. There were about a couple of dozen of these larvae (at least the ones I observed). Plenty of capped honey was in the hive so this was absolutely not brood eviction due to starvation, which is really where the brood is partly consumed as a resource. I wondered if these dragged larvae were because of the agitated bee behavior, and the bees failing to cap the brood cells at the proper time. Without a capping, the larvae (ready to spin their cocoons) would partly come out of their cells, and the bees might remove them.

Figure 4 shows Colony #14 late that night. First notice the bees covered the comb. Therefore, adult beetles gaining access to exposed comb because the colony was weak does not apply here. The area enclosed by the orange boundary was where the bees were particularly agitated. Late at night, the bees in the brood nest should be calm, mainly just tending brood. I denoted some of the larvae dragged by the bees on the glass. Figure 5 shows a closer view of the larvae. I have not seen numerous larvae treated in this manner. Figure 6 shows larvae clumped together found later on the floor of the hive, a new condition for me too.

Returning to Figure 4, the wire mesh brackets hold small pieces of pollen substitute. The bees consumed the right patty normally. The edges of the patty appeared as it did originally, indicating no beetle damage. The beetles have compromised the left patty in Figure 4. Notice the edge has a shiny appearance. Figure 7 shows a closer view. The bees have rejected the slimy edge as a….