A Grass carrying wasp and a Mud dauber in France

A couple of interesting introduced species in France that many people will have come across and which are noticeable due to their somewhat unusual behaviour.

Isodontia mexicana known as the grass carrying wasp and Sceliphron curvatum a “Mud dauber” have established themselves rather successfully in France. Isodontia mexicana can be found in all regions and Sceliphron curvatum is so far restricted to more or less the southern two-thirds of the country but the expansion is rapid.  Both belong to the Sphecidae which are a cosmopolitan family of wasps of the suborder Apocrita that includes sand wasps, mud daubers, and other thread-waisted wasps.

Isodontia mexicana arrived in Europe from North America in the 1960s. For several years, it remained confined to the Mediterranean region, but from 2003, a year which was particularly hot, it began to extend its range northward. It is currently found in France, Switzerland, Hungary, Italy and Spain. They are black with smoky brown wings and measure between 15 and 25mm with females being larger than males. The adults feed on nectar with plants such as mint, wild carrot and other umbellifers being especially favoured.

Females use existing holes or hollow plant stems as nest sites where she may create as few as 2 cells or as many as 8 cells depending on space available each cell being separated by plant fragments. Each cell is provisioned with a living grasshopper or cricket that has been paralysed and on which she places an egg thus providing the fresh food the larva requires for its development. Finally the hole is stuffed with dry grass or stalks, hence the common English name. Eggs that are laid late in the season will overwinter after sheltering in a cocoon they have spun (diapause) and emerge in May or June. Early broods at this time of year will produce a summer generation that develops in a few weeks giving us two generations in a calendar year. 

    Click photos to enlarge

Photos above of Isodontia mexicana & nests

If you have a “bee hotel” and live where there are plenty of grasshoppers there is a very good chance that they will use that. Only significant predators are thought to be birds.

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Sceliphron curvatum.  The native range of this species extends from Iraq to northern India and Nepal, and from Pakistan to Kyrgyzstan and eastern Uzbekistan.  The evidence points to the fact that it probably arrived in France a little before 2010 when the first confirmed identifications were made following a progression eastwards across Europe starting in Austria in the 1990’s that was not a natural occurrence. .

Adults are between 15 and 25mm. The thorax is black with 2 yellow bands and the abdomen is orange with dark reddish bands.

After mating, the female builds a nest of mud that is made up of several tubular cells, each in the region of 20mm long that are constructed progressively at the same time as being provisioned with an egg and its food supply. Each of these cells is intended for a larva. When each cell is complete, the female hunts and stores enough spiders, usually from 6 to 15 but can be as many as 40, to feed the larva until it is metamorphosed. Live prey is paralyzed, thus constituting a reserve of fresh food. Having laid the egg on one of the spiders she closes the cell with mud. She continues building the nest until it has about 25 cells.

The larvae develop during the course of a few weeks and then turn into pupae in their cell, where they spend the winter. Adults emerge from their cells in the spring.

The nests are often to be found in peoples homes attached to furniture, folds in curtains, clothing and so on. I have sometimes found them between the roof of a hive and the lid and it’s likely that they search out places that are both warm and dry.

Photos above of Sceliphron curvatum. and nests

As introduced species it’s hard to say how much impact either of them causes or could cause in the future for indigenous species.

Chris

House Centipede - la Scutigére, (Scutigera coleoptrata) in France

Older French stone built houses invariably play host to a number of species and that includes these fascinating little guests although not all people are thrilled by their presence or their speed when they get a move on reaching speeds of up to 0.4 meters per second.

Although in everyday usage they are called a centipede or “hundred feet” they actually only have 15 pairs of legs when fully grown giving them 30 legs. The last 2 legs are particularly long, longer in fact than their antennae reaching twice the length of the body and can be nearly 6 cm. They use these long legs to form a kind of lasso which is one of the methods they use to capture prey.

Note that the common terms centipede and millipede are never meant to be factual and both are grouped together as myriapods or very many-footed.

Eggs are laid in spring and the larvae when they hatch look like miniature versions of the adult but with only 4 pairs of legs. They gain a new pair with the first moult and two pairs with each of their five subsequent moults. Adults with 15 pairs of legs retain that number through three more moulting stages (sequence 4-5-7-9-11-13-15-15-15-15 pairs).  They have a lifespan that is from 3 to 8 years with sexual maturity reached in the third year.

Mating can be tricky with the male and female circling around each other making contact with their antennae with this being the only contact they will make. The male then deposits his sperm on the ground which the female collects and uses to fertilise herself.

Prey is killed or disabled using venom that is delivered using Forcipules which are a unique feature found only in centipedes and in no other arthropods. These are modifications of the first pair of legs that form a pincer-like appendage always found just behind the head.

Venom glands run through a tube almost to the tip of each forcipule. It’s highly unlikely that these would be used on a human being unless it was trapped with no available escape such as being held in a closed hand or caught in clothing. Prey can be almost any insect including wasps and hornets and as such they can be a useful creature to have around the home as they quietly go about their nocturnal searches for food.

Chris

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.

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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