Wax moth and Honeybees in France

Wax moths of both species Achroia grisella and Galleria mellonella which are commonly known as Lesser Wax Moth and Greater Wax Moth have one brood per year but this leads to successive generations as they complete their life cycle and the offspring breed. The adult moths live for about a week and are mainly nocturnal.

.

In both cases the development time between egg and adult hatching is temperature dependent and can vary considerably but can be as little as 45 days with an average daytime temperature of 28 – 30°C  but can take up to 7 or 8 months. Essentially higher temperatures speed up the development. Eggs always hatch in less than 2 weeks and it can be as little as 2 or 3 days.  The larval, (or grub), stage has the most flexible lifespan and generally the longest, anything from about 4 weeks to 6 months and of course as any beekeeper knows beeswax is their food. 

Click images to enlarge

Photo Wax Moth

Both species overwinter in the larval stage. This is usually from August or September to May when pupation takes place. Lesser Wax Moth is the earlier of the two to be on the wing from late May to September with Greater Wax Moth on the wing from July to October.

Photo Wax Moth Larva about to pupate

Photo of Wax Moth Pupae on hive frames

At no stage in their life cycle can they tolerate temperatures in excess of 45°C or below 0°C. This is important to know for beekeepers as it provides 2 methods to be certain that frames are clear of them. The frames can be frozen if they have comb in them and they can be gone over with a heat gun if they have no comb in them as can the interior of the hive. 

So we can see that there is really not a huge difference in their basic biology and life cycle. 

Now we come to the frequently misunderstood question of honeybees and wax moth.

Anyone that knows anything about honeybees will know that they are fastidiously hygienic in the management of their colony and the space it occupies including sealing all un-required spaces, holes and fissures with Propolis as well as coating the entire enclosed interior with a thin coat of it. Any damaged or unhealthy bee larvae and bees are continuously removed from the colony.  What this means is that there is absolutely no chance of wax moth establishing themselves in a healthy colony. Should a female moth sneak her way in and lay a few eggs they will be quickly dealt with. Any eggs that escape the cleaners and manage to hatch will be dragged out of the colony and dumped outside or if they are wedged in a small space they will be coated in Propolis.

Only when a colony has failed and died or is at the point of dying can wax moth move in and their larvae consume the old wax. This will not prevent a new swarm from occupying the hive or empty space; they will happily move in and within a day or two will have ripped out the entire damaged comb with any pupae and larvae that are present.

Photo contents of a Wax Moth infested hive ripped out of a hive by a swarm within 48 hours

Another possible point of entry for wax moth is following the extraction of honey from the honey supers, (the boxes that are placed on top of the main hive to collect honey). Careful extraction should result in very little damage to the comb allowing the same comb frames to be used again which requires that these be stored and kept in good condition over winter. Different beekeepers have their own methods of dealing with the extracted frames, some putting them back for a short while either over or under the actual hive for the bees to remove all the residual honey. I’m not a fan of this as it creates extra work with no obvious merit and as such I prefer to store my extracted frames “wet”, that is to say with the residual honey left in place on the frames. When these go back on the hives the following spring it encourages the bees to clean and restore any damaged comb.

The important thing is to store them free of wax moth by keeping the supers with the comb frames in them sealed immediately after extraction. This is not complicated, requires very little other than a little preparation. Bearing in mind that “wet” frames will drip a little I use a plain metal hive lid to put underneath and either another or a piece of flat plywood to put on top of each stack of supers making sure there are no gaps. Whether the supers and frames are stored “wet or dry” the same principle applies of making sure they are stacked and sealed immediately and not left lying around open to the air. 

Chris  

Map Butterfly - Carte géographique 2018, Blanzay, France

16^th September 2018

Overall this year has been very poor at our place for butterflies and moths with even our usual common species such as Speckled Wood, Meadow Brown, Large and Small Whites, Peacocks, Gatekeepers, Marbled Whites and Red Admirals all in short supply.

Early in the summer both types of Swallowtail made brief appearances as did Painted Ladies, a handful of Common Blue and Holly Blues whilst in June Some Lesser Purple Emperors graced us with their presence, always welcome as they come down from the treetops to search for minerals that they usually get from any excrement that is to be found. 

Click photos to expand.

Above -  Lesser Purple Emperor on dog excrement.

Anyway, the purpose of this little note is to mention one butterfly species that have been abundant here this year, in fact exceptionally so and that is the Map Butterfly, Araschnia levana, a pretty little butterfly that has two distinct forms, Araschnia.f. levana and Araschnia.f. prorsa that represent the spring and summer broods respectively. levana individuals are primarily orange in colour, giving them the appearance of a small fritillary, whereas prorsa individuals look more like a very small White Admiral and many people confuse them as such.

Above - Map butterflies 2nd generation

The eggs are laid in little strings bunched together under nettle leaves which are the caterpillar food plant in shaded or partially shaded areas. Late season caterpillars overwinter as pupae that emerge in the following April/May providing the first generation butterflies. The 2nd generation flies from June to August. In the South and Southwest of France a third generation may be produced in some years. The caterpillars in some stages bear some resemblance to Peacock caterpillars that share the same food plant of nettles so it’s worth a closer look.

 Above- Map butterfly caterpillar & Eggs

As mentioned there have never been so many here before for what has previously been a scarce species at our place where we rarely see more than a few in a season and it’s hard to see what if anything has changed. 

It is a species that may be benefitting from climate change, who knows? I'll see what happens next year.

Chris