The book scorpion (Chelifer Cancroides) – formerly also known as the mite wolf – belongs to the class of arachnids and to the order of pseudoscorpions. It is the most widespread pseudoscorpion. Currently about 3000 species of pseudoscorpions are known worldwide, about 100 from Central Europe. In different regions of the world, different types of pseudoscorpions are found in hives and beehives. Some Ellingsenius species in the southern hemisphere have specialised in honey bees and are found exclusively in bee colonies.
Book scorpions are useful animals for honeybees and beekeepers
The book scorpion (Chelifer Cancroides) feeds on parasites of bees in beehives, which makes it beneficial for honey bees and beekeepers. The bees tolerate them. The permanent settlement of the sensitive animals in hives has already been successful for me. Also I can prove by IR photos that the shy animals approach the bees and feel them. The proof of picking a Varroa mite is unfortunately not yet successful. But also regardless of that they are a welcome guest in the beehive!
Are book scorpions effective in the fight against the Varroa mites?
The effectiveness of the book scorpions in fighting the Varroa mite has not been proven. A sale of book scorpions and the assertion that they would significantly decimate the Varroa is wrong and does not serve the cause. There are only a number of indications that suggest efficacy. There are also indications in old literature that suggest that the book scorpion has taken a targeted removal of the varroa from the honey bees. The old and new references about the killing of parasites in the beehive of the western honey bee by the book scorpion are listed below:
Ludwig Koch: „Übersichtliche Darstellung der europäischen Chernetiden (Pseudoscorpione)“, Nürnberg, 1873
The first mention of the book scorpion as a roommate of honey bees can be found in the literature of 1873 in Ludwig Koch’s “Clearly arranged description of the European chernetids (pseudoscorpions)”. He mentions houses, insect boxes and mainly beehives as the places where they were found.
Alois Alfonsus: Der Feind der Bienenlaus, Deutsche Illustrierte Bienenzeitung, 8. Jahrgang, S. 503-506, 1891
In 1891 Alois Alfonsus wrote in a short article about the discovery of these insects in beehives and their hunt for bee lice and other small insects such as mites and dust lice.
Dr. Josef Fahringer: Beobachtungen über einige Bewohner von Bienenstöcken. 1. Bücherskorpione, Bienenvater 57, Seite 83-84, 1925
The strongest indication at that time for the removal of mites from the bee body by book scorpions was provided by Dr. Josef Fahringer in his experiment in 1925. He occupied the body of honey bees with mites which he had previously taken from the body of bumble bees. By administering a feed solution to the bees, he calmed them down. Now he directed book scorpions with light to the resting bees. Within a short time he was able to observe the removal of mites from the workers by the book scorpion.
I myself can prove with my infrared video recordings in beehives that book scorpions approach the bees fearlessly even under natural conditions and scan them. The bees let them do it. Fig. 4-6 are screenshots from infrared images in beehives, the complete videos can be found here.
Zoltán Örösi-Pál: Afterskorpione (Chelonethi) in der Wohnung der Honigbiene, Journal of applied entomology, Volume 25 S. 142-150, 1939
In 1939 Zoltán Örösi-Pál gives a detailed overview of the state of knowledge about pseudoscorpions in beehives worldwide. He writes that pseudoscorpions are mostly found on the cover boards, the wax cloth, the frame strips, the walls or on the bottom of the hive. He had never seen them on the honeycombs so far. I can confirm this observation, I have also never seen book scorpions moving across combs. I usually find them on the upper beams and on the bottom of the hive.
He further writes that no breeding nest has yet been found in beehives. We know more about this today (Fig. 1). The shy animals have managed to settle permanently in beehives. By suitable constructions with outside walls from straw, additional insulation from straw or for example a D-lid with straw filling this is possible.
In 1939 Örösi-Pál describes the general view at the time that the book scorpion even eats mites on bees and other small creatures. He found out in his own experiments that the book scorpion sucks out the caterpillars of the large wax moth, as long as they are not larger than 1 cm (Fig. 2). I can confirm this statement by my own observations in beehives and by experiments under laboratory conditions. I could also observe the book scorpion attacking significantly larger caterpillars. Obviously, the effect of his poison is not sufficient to paralyze larger prey. It frees its victims after a while if the desired paralysis does not occur, or the resistance is too strong due to the lack of paralysis (Fig. 3).
Örösi-Pál concludes his report with the knowledge that no harmful effect of pseudoscorpions against honeybees has ever been seen. It is not known whether pseudoscorpions read mites and aphids from bee bodies under natural conditions. Because of the consumption of mites, wax moth larvae, fallen aphids and other small creatures of the hive, pseudoscorpions are useful. Due to the limited number of pseudoscorpions in bee hives, however, their use has no practical significance.
Dr. Max Beier: Der Bücherskorpion, ein willkommener Gast der Bienenvölker, Österreichischer Imker, Jhg. 1, 1951, S. 209-211
The article by Dr. Max Beier from 1951 “The book scorpion, a welcome guest of the bee colonies” has received great attention to this day. It also describes its use by eliminating various parasites in the beehive. Without naming new sources or documents he expresses the assumption that the book scorpion takes parasites directly from the bees. Probably it refers here to the experiments of Fahringer.
His description how the animals see is very revealing: “He does not orient himself with his weak eyes, which are hardly suitable for seeing pictures, but with the help of long, straight tactile hairs, which are twelve times on the scissors fingers of the adult animal and respond even to the slightest air movement as a result of their movable insertion in large cups, so that they are also called hearing hairs with some right.” With my video recordings I can confirm that they use their tentacles to “see”. It becomes particularly clear when they are in a slit with their bodies and use their tentacles similarly to periscopes on submarines (Fig. 7). Before they leave a slit they stretch a tentacle into the room and “look around”.
He also describes how the book scorpion stuns his victims, pierces them with his jaw scissors and lets gastric juice flow into the wound. He then slurps up the meat parts liquefied by the gastric juice and consumes them. In Figure 8 I have recorded this observation, described by Max Beier as early as 1951, under the microscope.
Unfortunately I could not observe the phoresia described in the article so far. Beier writes that especially during the swarming period book scorpions can be found that cling to one leg or another part of the bee’s body with their palpist scissors and can thus be carried in flight. This behaviour – a kind of wandering instinct – is triggered by the resulting restlessness in the bee colony shortly before swarming. According to Beier, it is always pregnant females, that are found as flight-passengers in such a way like this and provide for the spread of the type in this way.
In his article, Baier also describes the laying of eggs by pregnant females of up to 20 eggs, the construction of breeding and moulting nests, hatching and the development of young animals. Finally, he dedicates himself to the Ellingsenius species found in hives in the southern hemisphere, to which he attributes a more important role as pest controllers and health police in the hive than the book scorpions native to our country.
Dr. Peter Weygold: Moos- und Bücherskorpione, Neue Brehm Bücherei Wittenberg, 1966
1966 The book “Moos- und Bücherskorpione” by Dr. Peter Weygold is published. It is still the most comprehensive description of these book scorpions in the german language. Unfortunately, he does not look any further at the life of the book scorpions in bee hives and mentions this context only marginally.
Barry Donovan & Flora Paul: Pseudoscorpions: the forgotten beneficials inside beehives and their potential for management for control of varroa and other arthropod pests, Bee World, Volume 86, 2005
In 2005 the article “Pseudoscorpions: the forgotten beneficials inside beehives and their potential for management for control of varroa and other arthropod pests” was published in a Bee World magazine. It deals with the question whether the Chelifer Cancroides (the book scorpion) and other pseudoscorpions related to him, which have fallen into oblivion in Europe, are suitable worldwide for combating varroa mites and other parasites. According to the authors, the book scorpion has fallen into oblivion in Europe because it has hardly been found in modern beehive systems. They suspect the reason for this in the displacement of the log hives and straw hives by magazine hives with their movable frames, made of smooth sawn wood. After the appearance of the Varroa mite in Europe, the chemical treatment in the bee hives might have finally banished the book scorpions from the hives. The authors suspect that at least some species of pseudoscorpions could prove to be effective controllers of Varroa and other pests of honeybees if they are present in sufficient numbers in hives.
Torben Schiffer: Biologische Untersuchungen an mit Honigbienen assoziierten Pseudoskorpionen (Chelifer cancroides), Staatsexamensarbeit im Fach Biologie, 2008, Universität Hamburg
In 2008, Torben Schiffer picked up this topic in his State Examination work in biology. Interesting here are details about the requirements for the habitat of book scorpions and about Torben Schiffer’s methods of catching these shy animals. In his “further research work”, Torben Schiffer undertakes symbiotic experiments. He succeeds in making book scorpions reproduce in bee hives. He cannot establish any efficacy in the fight against varroa.
Ron van Toor et al.: Ingestion of Varroa destructor by pseudoscorpions in honey bee hives confirmed by PCR analysis, Journal of Apicultural Research 54(5):1-8, 2016
In 2016, Ron van Toor uses DNA analysis to prove the consumption of varroa mites in conventional magazine hives by book scorpions. However, the eaten mites could have fallen naturally and already been removed from the reproduction cycle. It is therefore not a proof for the effectiveness of the book scorpions in the fight against varroa.
Hans-Jürgen Ratsch et al.: Bücherskorpione als Varroabekämpfer – Endbericht zum Forschungsprojekt der Integrierten Gesamtschule List und der Schülerfirma Imkerei e.G., 2018
The experiments “Book Scorpions as Varroa Fighters” from 2018 gives hope for an effectiveness of the book scorpions. Here a lower natural mite infestation in wooden hives with book scorpions compared to wooden hives without book scorpions is noticed. The authors see this as proof of the effectiveness of book scorpions. I do not see it that way. The fallen mites were only counted once a week, which could have resulted in the following possible falsification: Since the book scorpions prefer to be at the bottom of the beehives, it is very probable that they took living mites from the board, which without their intervention would later have been counted as dead mites. So fewer mites are counted than actually fallen. Such mites falling alive (partially injured) on the board have already been removed from the reproduction cycle of the varroa in the bee colony, their removal by the book scorpion is of no use in the fight against varroa. In order to rule out this falsification, the control boards should be checked much more frequently, perhaps even several times a day. A clearer indication of the effectiveness of book scorpions is the lower mortality of colonies with book scorpions. However, the number of colonies investigated is too small to prove the effectiveness of book scorpions.
Building bee hives for the integration of book scorpions
Book scorpions can easily be placed in the lid or at the bottom of the hive. They prefer to stay above or below the hive. Above the hive you can use a D-lid with a straw filling. The bottom of a bee hive with book scorpions should be closed. Here, for example, you can fill a honey chamber with straw.
Finding places and cultivation of book scorpions
The best place for breeding book scorpions is surely the environment of naturally kept animals troubled by small parasites. Beehives are the perfect place (if the bees are kept untreated) with appropriate conversions/additions of the beehive. Chicken stalls, hay floors and grain storehouses close to animal stables also offer excellent conditions. Whoever wants to breed them far away from these places in separate boxes must reproduce the same conditions.
Book scorpions can be found at the places mentioned above. Here they can be found under objects and wood lying on the floor. The sensitive animals should be taken up with a fine brush. They are easy to transport in preserving jars with rubber seals.
Do book scorpions consume the little hive beetle?
Sooner or later the small hive beetle will probably also be native to us. It is very likely that the book scorpion also feeds on its larvae. These are much easier to reach than the Varroa mites sitting on the bees.