© Entomologica Fennica. 18 December 2013

Factors restricting the abundance of colonies of the European Vespa crabro and the Saxon wasp saxonica (: ) in an urban area in Poland

Jerzy Nadolski

Nadolski, J. 2013: Factors restricting the abundance of wasp colonies of the Eu- ropean hornet Vespa crabro and the Saxon wasp (Hy- menoptera: Vespidae) in an urban area in Poland. — Entomol. Fennica 24: 204– 215. Various factors affecting the reproductive success of Vespa crabro and Dolicho- saxonica (), including their parasitoids, parasites, pathogens and other accompanying their nests in the city of £ódŸ in Poland were investigated. Sphecophaga vesparum, sociella and especially Quedius brevicornis, whose larvae cause destruction of wasp nests, were re- corded. Totally 19 species or groups of bacteria, including pathogens like Pseu- domonas aeruginosa, Enterobacter cloacae, and Entero- coccus faecalis, and 5 species of fungi were identified. Cities create very good conditions for wasp societies. Unfortunately, their presence can cause specific but important risks to humans, which lead to massive destruction of wasp nests. However, this does not cause considerable decrease in the number of colonies of common wasp species but less abundant species may be endangered in cities by this practice. It is thus recommended to limit the number of all wasp nests de- stroyed and to discriminate between the species. J. Nadolski, Faculty of Biology and Environmental Protection, Natural History Museum, University of £ódŸ, Kiliñskiego 101, 90–011 £ódŸ, Poland; E-mail: [email protected] Received 12 February 2013, accepted 22 May 2013

1. Introduction impacts on the effective colonization of cities by many species of social . The most charac- The presence of wasps (Vespinae) in cities is well teristic features of these areas are a warmer and known. As a result of numerous and extensive more stable microclimate than in other environ- studies, the current species composition and po- ments, varied and abundant food resources and a pulation dynamics of this group of are large variety of niches to be used (Christie & known in many urbanized areas (Haeseler 1982, Hochuli 2008). Skibiñska 1987, Kowalczyk 1991, Pawlikowski Different activities and methods aimed at re- & Osmañski 1998, Nadolski 2004, Pawlikowski ducing the presence of social wasps in cities has et al. 2005, Ahrné 2008). However, it is still diffi- increased in recent years. In Poland, different mu- cult to determine which factors have important nicipal departments, including the Fire Brigade ENTOMOL. FENNICA Vol. 24 • Wasp colonies in an urban area in Poland 205 and disinfestation companies, are hired to elimi- cally and only the few old city parks can create nate nests of bees and wasps. What is the real ex- specific living conditions for different species of tent of these events? Do people and natural ene- wild fauna. The centre of the city is surrounded mies of wasps, i.e. predators, parasites and by residential zone with housing estates, modern parasitoids, have an important impact on the exis- blocks and skyscrapers as well as by industrial tence of social wasps in cities? areas. Despite the presence of a large number of Studies of accompanying fauna of social Hy- young trees and green areas, this zone is rather menoptera have been conducted for the nests of poor and monotonous. The large forest in the Apidae (Banaszak 1980, Schmid-Hempel 1998), north of the city (£agiewniki forest) and areas of Formicidae (Staniec & Zagaja 2008) as well as detached houses, old farms and wastelands sur- various groups of Vespidae (Nadolski 2004). round the whole town and have a direct contact However, only those organisms can be a threat to with woods and agricultural lands located outside societies of wasps, which limit development of the city. colonies or can destroy them. These are para- sitoids, parasites and pathogens (Schmid-Hempel 1998, Rose et al. 1999). In addition, the presence 2.2. Data collection of different microorganisms in nests of social Hy- menoptera can be a potential threat to humans due When young queens of wasps begin the building to human-related pathogenity, especially when of nests in the spring, they choose different places nests of wasps are established in the immediate which are characteristic for a particular species. vicinity of human’s premises. Based on studies in the years 2000–2009 the pre- The purpose of this study was to assess the ex- ferred nest sites of the both studied species of tent and impact of the above described phenom- wasps were examined. Every place was classified ena and their importance for the life and develop- as belonging to one of the two categories, natural ment of the urban colonies of two species of or buildings. Places classified in the first category Vespinae wasps, Vespa crabro (Linnaeus, 1758) were ‘natural’ ones, which were not inhabited by and Dolichovespula saxonica (Fabricius, 1793), humans or associated with their activity, such as as well as to qualitatively characterize the para- different types of buildings and equipment of the sitoids and parasites as well as pathogens and city infrastructure. The only exception were bree- other microorganisms in their nests. These issues ding boxes for birds, which, because of their con- are certainly relevant for the safety of the urban struction resembling hollows of trees, were also human population, but the assessment of these categorized as ‘natural’. To the second category, risks is beyond the scope of this study. ‘buildings’, belonged places directly related to the structure of the urbanization of the city: resi- dential buildings and outbuildings with the asso- 2. Material and methods ciated infrastructure were included. Information about the locations of wasp colo- 2.1. Study area nies were obtained from the municipal and forest services as well as from the telephone notification Colonies of two species of wasps (Vespinae), the and survey data from citizens of £ódŸ and as the (Vespa crabro) and Saxon wasp author’s own observations (Nadolski 2012). (Dolichovespula saxonica), were studied in Empty nests in the stage of initiation were not in- 2000–2009 within the administrative area of the cluded. After verified, data were entered into a city of £ódŸ, covering 294.4 km2 of land. £ódŸ specially created database in Access (Microsoft has a characteristic structure with the buildings of Inc. 1997, 2000). the city connected by the concentric location of Colonies of the two studied species were streets and houses. The town centre is an area of found from different places of the city. The Euro- dense development with the old buildings origi- pean hornet is a large wasp and finding and iden- nating from the turn of the 19th and 20th centu- tification of its nests are very easy. However, all ries. This area is poorly differentiated biologi- received information was checked. While being 206 Nadolski • ENTOMOL. FENNICA Vol. 24

Table 1. Success of Vespa crabro and Dolichovespula saxonica colonies established in natural places and buildings in the city of £ódŸ in 2000–2009. a. Nests destroyed by humans

Vespa crabro Dolichovespula saxonica

Destr. Not Total Destr. Not Total

N % N % NN% N % N

Natural places 4 11 34 89 38 8 7 106 93 114

Buildings 265 81 62 19 327 232 75 77 25 309 ¤2 83.7, p<0.001 154.4, p<0.001 b. Nests with reproductive castes present vs. not; nests without reproductive castes became extinct or abandoned

Vespa crabro Dolichovespula saxonica

Present Not Total Present Not Total

N % N % NN% N % N

Natural places 12 35 22 65 34 17 16 89 84 106

Buildings 59 95 3 5 62 76 99 1 1 77 ¤2 37.8, p<0.001 101.2, p<0.001 aware of possible defects of these methods of col- wasp is much more difficult, and hence the above lecting data about nest locations, only these were described method can be unreliable. Therefore, feasible in practice, and made it necessary to esti- the total number of colonies of this species in the mate the possible error in the assessment of nest city of £ódŸ, in particular years, could not be de- numbers. Note that the city of £ódŸ is large (al- termined. Some nests could not be examined in most 300 km2) with a dense urban structure and detail because they were in inaccessible places. multiple industrial and agricultural areas as well Other nests, both active and empty, were sub- as forests and parks. Therefore, a detailed inven- jected to a thorough examination. Thus, the real tory of all hornet nests was carried out in ran- total number of colonies of this species in the city domly selected 10 squares, each with an area of 1 of £ódŸ may have been up to several dozen per- km2 (Nadolski 2012). Effort was made in these cent higher in each year than shown in this study. squares to record all nests of Vespinae, particu- However, the proportions in the location of the larly colonies of V. crabro and compare the data nest (natural and buildings) are rather constant. obtained in this way with the number of colonies Active colonies of wasps were removed by from the same squares noted as a result of notifi- enclosing each nest as a whole into a plastic bag cations, surveys, and data obtained from all of the and cutting it from the place of suspension. Some- municipal services. It turned out that in the case of times, in the case of large societies, the fire extin- V. crabro only few nests established on the pre- guisher with carbon dioxide to freeze or insecti- mises of abandoned factories and fallow lands cides to kill the wasps in nests was used. After re- were not included in the notifications. These moval of the nests, the whole colonies were kept studies showed very high, over 90% effective at –18°C. Because of the need to collect all indi- registration of the colonies of the hornet in the viduals of the societies, the sampling of the nests city. was carried out at nights. Besed on detailed stud- To locate and recognize nests of the Saxon ies of the nests, the degree of development of the ENTOMOL. FENNICA Vol. 24 • Wasp colonies in an urban area in Poland 207

Table 2. Causes of natural death of societies of Vespa crabro and Dolichovespula saxonica in the city of £ódŸ in 2000–2009.

V. crabro D. saxonica

Weather 3 16 Parasitoids, parasites and predators Sphecophaga vesparum 023 Aphomia sociella 024 S. vesparum + A. sociella 04 Quedius brevicornis 30 Mammals 3 4 Queen failure Death 7 11 Usurper 2 2* Broken nests or nest boxes 3 2 Cause unknown 1 3 Fig. 1. Cells from a nest of Dolichovespula saxonica attacked by Sphecophaga vesparum. Total 22 89

* Dolichovespula adulterine substrates of the company Bio Merieux were used: Columbia Agar with 5% Sheep Blood (a colonies (the presence or absence of reproductive general purpose culture medium used for the castes) as well as their condition (presence or ab- growth and recovery of fastidious microbial spe- sence of the queen, presence of parasitoids, phys- cies including Streptococcus pneumonia, Staphy- ical destruction of the nest by predators or munic- lococcus aureus and ), Mannitol ipal services etc.) were determined. A total of 365 salt agar (MSA, containing pancreatic digest of nests of the European hornet and 423 nests of casein, peptic digest of tissue and beef ex- Saxon wasps were examined (Table 1). A de- tract) for the isolation and enumeration of patho- tailed description of the methods of the analysis genic staphylococci, MacConkey’s Agar (a spe- of the nests of wasps is presented by Nadolski cial bacterial growth medium that is selective for (2012). Gram-bacteria and can differentiate those bacte- In the studies of microorganisms of the nests ria that are able to ferment lactose) and D- of Vespinae, both the colonies of D. saxonica and coccosel agar (for selective isolation and differ- V. crabro were used. These studies were carried entiation of enterococci and group D strepto- out during the years 2000–2003, 2007 and 2008. cocci). Altogether, 22 nests of V. crabro and20nestsof In addition, substrates of the company Ema- D. saxonica from different areas of the city were pol were used: Mannitol Salt Agar (MSA) (a studied. They were located in residential and util- commonly used growth medium in microbiol- ity buildings as well as in nesting boxes for birds ogy) and Sabouraud Dextrose Agar (a type of and different natural places (branches and hol- agar containing peptones, used to cultivate der- lows of the trees, holes in the ground). For quali- matophytes and other types of fungi). For isolat- tative microbiological tests, swabs were collected ing and marking of the bacteria of Enterobacteri- from both the empty and active nests. The swabs aceae family, substrates of tryptone-tryptophan were taken from the outlets of the nests, from the from the company Graso and identification tests surface of the workers returning to the nests, as EPL – 21 from the company HTL were used. well as from the accumulated below the Statistical analyses were conducted using nests, and in the case of empty nests, from the sur- STATISTICA 9 package (StatSoft, Inc. 2010). face of the combs and interior of cells. The chi-squared tests were performed using For the culture of microorganisms, the solid Yates correction. 208 Nadolski • ENTOMOL. FENNICA Vol. 24

Fig. 2. A nest of Doli- chovespula saxonica destroyed by larvae of Aphomia sociella.

3. Results In Table 2, the causes of natural dying out of the societies of D. saxonica and V. crabro in the The number and percentage of nests of both city of £ódŸ are presented. In Saxon wasp’s nests V. crabro and D. saxonica destroyed by humans the following parasitoids, parasites and predators depended on their location (Table 1a). Colonies were found in £ódŸ: the parasitic wasp Spheco- established in buildings were destroyed more fre- phaga vesparum (Curtis 1836) (Hymenoptera, quently than the ones in natural places. However, ) (Fig. 1), bee moth, Aphomia so- the number and percentage of nests which were ciella (Linnaeus 1758) (, ) not destroyed and completed their development (Fig. 2) and parasitic yellow-jacket, Dolicho- and obtained reproductive castes was also signifi- vespula adulterina (du Buysson 1905) (Hyme- cantly higher in buildings than in natural places noptera, Vespinae). (Table 1b). In the nests of the European hornet, larvae of

Fig. 3. A comb from a nest of Vespa crabro destroyed by larvae of Quedius brevicornis. ENTOMOL. FENNICA Vol. 24 • Wasp colonies in an urban area in Poland 209

Table 3. Microorganisms isolated from colonies of Vespa crabro and Dolichovespula saxonica in the city of £ódŸ.

Vespa crabro Dolichovespula saxonica

Natural places Buildings Natural places Buildings

Nests Detritus Nests Detritus Nests Detritus Nests Detritus

Pseudomonas aeruginosa x Escherichia coli xxx xx E.blattae xx x Citrobacter freundii x C. diversus xx Klebsiella pneumoniae x K. oxytoca xx x Enterobacter cloacae xxx Proteus mirabilis x P. vulgaris xx Pantoea agglomerans xx xx Staphylococcus aureus xx x S. epidermidis xxxxxx S. saprophyticus xx xx Enterococcus faecalis xxx xx Enterococcus sp.xxxx Gram-positive bacilli x Gram-negative bacilli x Gram-positive rods x xxxx xxxx Penicillium sp. xxxx xx x xx C. glabrata xx C. albicans xx x the beetle Quedius brevicornis (Thomson, 1860) found that larvae of Q. brevicornis produced a (Coleoptera, Staphylinidae) were found (Table 2) very specific odeur in nests of V. crabro.These (Fig. 3) in nests which were located in nesting are the first described cases of predation by larvae boxes for birds in the £agiewniki Forest and Bo- Q. brevicornis on larvae and pupae of V. crabro. tanic Garden in the £ódŸ. For the purpose of The last group of which can be proper taxonomic designation, larvae of rove- ‘blamed’ for destroying wasps’ nests are mam- beetles from hornet nests were bred. The larvae of mals. In £ódŸ, two nests of V. crabro located un- Q. brevicornis were found both in the detritus be- derground that were destroyed by foxes (Vulpes neath the hornet’s nest and in lower combs which vulpes L.)orbadgers(Meles meles L.) were adjoined to the bottom of the nesting box. In these found, and five nests of both species of wasps in combs, the cells were used for larvae of the repro- buildings or tree hollows probably destroyed by ductive castes – gynes (young queens) and martens (Martes sp.) were observed (Table 2). drones. Due to aggressive foraging by the larvae A total of 19 species or groups of bacteria in- of Q. brevicornis, the combs placed the lowest cluding pathogens like Pseudomonas aerugino- were severely damaged and the hornet’s larvae sa, Klebsiella pneumoniae, Enterobacter cloacae and pupae in them were completely destroyed Staphylococcus aureus and Enterococcus faeca- (Fig. 3). Moreover, because workers of V. crabro lis and 5 species of fungi were identified in nests cut off access to the affected combs, those could and in detritus in colonies of the European hornet not be cleaned. In these parts of the nests there and Saxon wasp (Table 3). Especially detritus lo- was a serious secondary infection by fungi, which cated directly under the nests was contaminated further increased the loss of these colonies. It was with microorganisms. 210 Nadolski • ENTOMOL. FENNICA Vol. 24

4. Discussion can therefore not only be explained by a limited number of available natural places for the nests, 4.1. Urban areas as nestinghabitats but probably also by their quality. Places in build- for social wasps ings provide a relatively stable temperature, pro- tection from precipitation, predators and also Large cities provide an environment in which probably against the different parasitoids as they habitat types are dependent on the degree of ur- were not observed in the wasp nests located in banization. For many species of social wasps the buildings. Anyway, the lack of parasitoids in the fundamental feature of this environment is unlim- buildings is to some extent consistent with results ited number of sites to establish colonies and a of other studies (Kowalczyk 1991), in which a wealth of food availability which is also often un- smaller number of parasitic species was recorded limited (garbage, food warehouses). This seem- in the centre of £ódŸ than in non-urban areas. ingly idyllic picture of the city as an ideal place Colonies of wasps in buildings may also reach for the existence of colonies of wasps is disturbed much larger sizes than those in natural places, and by people living there, who in most cases are re- they can achieve higher reproductive success, be- luctant and hostile towards such neighbours. The cause the number of all individuals of a particular European hornet and the Saxon wasp most often society, including sexual castes, is closely corre- establish their colonies in forests (Pawlikowski lated with the nest size (Jeanne & Bouwma 2002) 2009). However, in urban areas their nests can of- which has been confirmed also in studies by ten be found inside residential and utility build- Nadolski (2012). ings. Accordingly, the studies by Nadolski As shown in the present study, one of the (2012) demonstrated that urban populations of causes limiting wasp colonies is weather condi- both V. crabro and D. saxonica prefer places in tions, which may sometimes contribute to prema- residential and utility buildings and other accom- ture death of the whole society of wasps. Accord- panying urban infrastructures to more natural ing to the present study and the author’s other ob- places. Buildings and the entire infrastructure as servations, long-lasting and heavy rain and strong places for wasp nests allow the formation of winds can cause the destruction of nests and elim- larger colonies and create better conditions for the inate colonies completely, especially those which development of their societies. Therefore, colo- were created in underground burrows or on nies of wasps established in these places are branches of trees and bushes. Nests which are lo- larger and more numerous than those outside the cated on branches of trees are often washed away urban areas (Nadolski 2012). It seems that the key by rain or damaged by the wind, and those located element conditioning reproductive success of underground are flooded by water. Low rainfall Vespinae is the choice of place to build a nest, does not pose direct threat to a colony, but long- made in the spring by the young queen. lasting and high humidity leads to proliferation of The preference for buildings and other con- pathogenic fungi (Table 3), which destroy both structions as nest sites in urban areas is under- the structure of a nest made of a delicate material standable, because the number of natural places is resembling paper, as well as larvae and pupae limited there, while in buildings there are plenty within it. of them. However, sometimes there are situations in which the number of natural places for nests is sufficient. This applies especially to both studied 4.2. Accompanyingfauna of wasp nests species which, according to their biology, usually build their nests on the branches of trees (Saxon Apart from the weather, parasitoids can be an wasp) or in the hollows of trees (both species) as equally important factor limiting the number of well as in underground burrows (the European Vespinae nests. Species of parasitoids which hornet). Why then these ‘tree hollow’ wasps pre- were found in nests of D. saxonica in the city of fer attics of buildings and sheds for their nesting, £ódŸ are well known (Schmid-Hempel, 1998). although many wooden nest boxes were sus- Some of them, especially the parasitic wasp pended nearby? The cause of the observed trends Sphecophaga vesparum, of which a few subspe- ENTOMOL. FENNICA Vol. 24 • Wasp colonies in an urban area in Poland 211 cies are known (Berry et al. 1997), have been suc- saxonica, but the presence of D. adulterina in cessfully used against species of wasps, which £ódŸ may be threatened by the massive destruc- are considered as , especially tion of nests of their hosts. German wasp () and the com- In studies of V. crabro nests, its accompany- monwasp(V. vulgaris), and the presence of ing fauna has rarely been investigated. However, which has become a serious problem for the resi- the presence of many representatives of different dents in New Zealand (Barlow et al. 1996, Harris animal groups, especially insects, has been & Read 1999). This ichneumonid has been re- shown in its nests (Schmid-Hempel 1998, Papp corded in Poland in the nests of D. saxonica in 2000), among others, numerous larvae of dipter- some areas, for example Borecka Primeval Forest ans (Diptera) and beetles (Coleoptera) feeding on (Pawlikowski & Pawlikowski 2003), Kampi- detritus located directly under the nest, as well as noska Primeval Forest (Sawoniewicz & Wiœni- predatory species which hunt on them. Some owski 2007) and in the city of £ódŸ (Nadolski rove-beetle species (Staphylinidae), first of all 2004). The effectiveness of this ichneumonid in known from underground burrows of mammals destroying wasp colonies is moderate and de- (Nowosad 1990) and nests of birds (Majka et al. pends primarily on the degree of development of 2006), have been found in nests of social wasps the infected societies. The earlier the infec- (Staniec & Zagaja 2008). tion happens, the more effective and dangerous The beetle Quedius brevicornis (Thomson, this action is to the host. 1860) was found in the nests of in the area The situation is different, when a wasp colony of £ódŸ. It is an uncommon species in , in is attacked by the moth parasite Aphomia sociella Poland known from a dozen locations (Staniec (Pyralidae), which has often been recorded in Po- 2003). Larvae of this species were known as com- land (Pa³ka 2000). Its effectiveness in destroying mensals which feed on the detritus in wasp nests, wasp nests is 100%. Caterpillars of this moth to- but detailed biology of the species is not yet fully tally destroy the nest structure, including combs known. It is interesting that in certain cases it may and envelopes (Fig. 2). Thus, the level of destruc- also be a predator whose larvae feed on larvae and tion is high enough to cause complete annihila- pupae of V. crabro. Because they can gnaw the tion of the society at any stage of its development. walls of cells and combs in hornets’ nests (Fig. 3) Its presence absolutely disorganizes the work of and they can move quickly, larvae of this beetle the whole wasp colony and causes various kinds are not attacked by workers of hornets. The de- of anomalies in the constructions of combs. The struction of hornet’s nest by larvae of Q. brevi- destructive activity of this parasite eventually cornis were observed only in boxes for birds, in leads to the physical destruction of the nest. The which, due to the limited space, larvae of the bee- presence of A. sociella in nests of the Saxon tle were able to attack low-positioned combs that wasps in the £ódŸ has always resulted in total de- were located directly above the bottom of boxes. struction of the whole colony. Because larvae and pupae of gynes and drones The abundances of S. vesparum or A. sociella were placed in these cells, the destruction caused in £ódŸ have not yet been carefully determined. by the larvae of the beetle was so huge that it led According to the author’s observations it can be to the total extinction of the colonies. Workers concluded that both species are rather common tried to save the hornet nest by isolating the within the administrative boundaries of the city, threatened area of the nest and by building addi- although they are not easy to find. tional envelopes which limited the area occupied In contrast to the two species above, the para- by larvae of Q. brevicornis. These actions caused site found in this study, Dolichovespula adulte- the death of all isolated larvae, which ceased to be rina, is a rare species of wasp in £ódŸ. It is a well- fed as well. In all cases of the presence of the lar- known social parasite of D. saxonica and Doli- vae of this beetle in a hornet nest, all wasp larvae chovespula norwegica (Fabricius 1781) (Dvoøák and pupae of the reproductive castes were eaten 2007). In this study, two colonies of D. saxonica by larvae of the rove-beetles in the end. Based on parasitized by D. adulterina were found. This these observations it may be assumed, that Q. species is not a threat to the population of D. brevicornis can be a dangerous beetle to hornet 212 Nadolski • ENTOMOL. FENNICA Vol. 24 only in nests located in spaces, where sizes and Candida krusei, C. glabrata and C. albicans development of colonies are limited by the vol- which may be sources of many different infec- ume of these places (in this case these were the tions and allergy. breeding boxes for birds). In a large tree hollow or The above pieces of information should be in the attic of a building, where combs of the nest important for guiding epidemiological preven- have no contact with the place on which the detri- tion. It is hard to directly blame wasps for the si- tus is gathered, the larvae of Q. brevicornis prob- tuation, because, as have been shown, the cause ably do not attack the larvae and pupae of hornets. of the problem rather lies in the fauna accompa- Plundering of nests of wasps by mammals nying the colonies of these insects. On the other were limited to only few cases where the colonies hand, without wasp colonies there would not be were destroyed by martens (Martes sp.) and the accompanying fauna either and thus no mi- probably foxes (Vulpes vulpes) and badgers croorganisms. The nests of the studied species of (Meles meles) (Table 3). Accordingly, it can be Vespinae, especially when established in natural assumed that these predators do not have a sub- places are bacteriologically cleaner. This indi- stantial impact on the size of populations of cates that the sources of infection does not need to Vespinae in £ódŸ. be the wasps, but could be other saprophytic in- sects, which eat excrements of wasps. The fauna accompanying nests of social wasps is rich, as 4.3. Accompanyingmicroorganisms discussed in the previous section, and except for in wasp nests parasite species, most of them feed on detritus. As mentioned, active nests are bacteriologi- It is common knowledge that colonies of wasps cally rather clean but in the empty nests, more can cause serious problems for people, the main types of microorganisms were found. Very strong residents of the city. Apart from poison- fungal growths on empty nests were often ob- ing, colonies of wasps in urban areas can cause served by the author of this study. It can be as- other serious problems. The present study dem- sumed that the purity of active nests is maintained onstrated the presence of many pathogens in the through the intense work of the workers that nests of wasps, especially in the detritus accumu- probably clean the combs and cells in their nests lated under the nest. Very often, the presence of from microorganisms through using the venom. colonies of wasps in a house is ascertained by de- The toxin of V. crabro demonstrates bacterio- tection of stinking stains on the ceilings and static properties, especially the mastoparan con- walls, over or near the location of the nest. Micro- tained in their venom. These properties have been organisms, which were found in the nests (Table found in toxins of many species of insects 3), can be a real threat not only for the wasps (Stocker & Traynor 1986, Yibin et al. 2005, Xu et themselves (Schmid-Hempel 1998, Rose et al. al. 2006, Chen et al. 2008). 1999), but also for the people. The presence of Interesting examples of bacteria are the spe- numerous pathogens in the wasp nests were cies of the Enterococcus (Enterococca- found, including ceae), which were always present in cultures of which can be an important cause of infection of microorganisms from nests and individuals of the the people, Staphylococcus aureus, a dangerous European hornets. It can be argued that they are bacterial purulent, Escherichia coli, Klebsiella symbiotic bacteria always present in the gastroin- pneumoniae and which often testinal tract of the hornet, similarly as they can be cause urinary tract infections, faecal bacteria in other species, such as the Asian hornet, Vespa Enterobacter cloacae and Enterococcus faecalis, orientalis (Linnaeus, 1771), for example (Ishay et and various species of fungi, including Asper- al. 2003). It is possible, that these symbiotic bac- gillus niger which produce aflatoxins causing re- teria protect larvae of wasps from fungal infesta- spiratory diseases and candidiasis, as well as tion (Kaltenpoth et al. 2005). ENTOMOL. FENNICA Vol. 24 • Wasp colonies in an urban area in Poland 213

4.4. Conflict between wasps nesting are people who in most cases do not even try to in buildings and humans tolerate a colony of insects in their neighbour- hood. Still, as shown above, wasps prefer objects The presence of social aculeates in urban areas created by people for their nest sites. The conflict has many consequences, some of which are still of the interests is obvious, and the insects are most underestimated, and others that can cause exces- at risk. The numerous and common species of sive concern among people, disproportionate to Vespinae can cope quite well in these conditions, the real threats. The scale of these phenomena is and as it seems, a quite large number of their colo- so serious that in Poland the Fire Brigade Head- nies remains in relatively similar numbers from quarters had to develop special procedures to be year to year. As an evidence of this there are simi- used for these types of threats (£yszkiewicz & lar numbers of interventions of municipal ser- Nadolski 2009). These rules are intended in a log- vices each year (Nadolski, unpubl.). A more im- ical way to limit the scope of intervention carried portant problem may be to keep other, less nu- out by the fire brigades, to the cases important for merous species of social wasps in the city, which social reasons. However, the question arises, are recorded in £ódŸ only occasionally and spo- whether this threat is so great that it is necessary radically. These are the , Dolicho- to use municipal services? Studies on honeybee vespula media (Retzius, 1793), the tree wasp, D. (Apis mellifera Linnaeus) in £ódŸ (Nadolski sylvestris (Scopoli, 1763) and the red wasp, 2008) showed the acceptance of the presence of Vespula rufa (Linnaeus 1758), as well as the spe- bee colonies by people, although their colonies cies classified as social parasites of yellow-jack- are more dangerous than those of wasps, because ets: (Bischoff, 1931) and honeybee venom is stronger and more often D. adulterina (du Buysson, 1905) (Nadolski, causes allergy than toxins of wasps (Habermann unpubl.). 1972, Banks & Shipolini 1986, Schmidt 1986, It is difficult to take a stand on what should be Antonicelli et al. 2003). done with colonies of wasps in urban areas. They In the present study, the percentage of societ- are, unfortunately, the neighbors that cause so ies in which the reproductive castes appeared was many problems for people but the mass extermi- small, only about 20%. Moreover, these societies nation of their nests can lead to the total elimina- of wasps, in the majority of cases, were not estab- tion of some of the species of social wasps from lished in natural places but in buildings where urban areas. It seems that the most appropriate ap- colonies of V. crabro were destroyed in over 80% proach would be to limit the extermination of the of the cases and those of D. saxonica in about nests only to the cases of their presence in the im- 75% (Table 1). Given that approximately 60– mediate vicinity of people, especially where there 70% of all colonies of both studied species of are many people (schools, hospitals). Maybe it wasps were destroyed by municipal services or would be worthwhile to consider installing in the the owners of buildings, the real picture that future special large nesting boxes for wasps in emerges from this study indicates the scale of the places where they would not be dangerous to hu- problem concerning the survival of urban popula- mans. tions of wasps. In all Polish cities in 2009 only, there were almost 80 thousand interventions of Acknowledgements. The author thanks prof. Bernard the Fire Brigade in relation to the risks arising Staniec for valuable tips on breeding and identification of from the presence of nests and swarms of social larvae and adults of the beetle Quedius brevicornis,the insects. It must be remembered that each of these team of the Laboratory of Microbiology Department of interventions meant destruction of an insect col- Laboratory Diagnostics ZOZ £ódŸ-Œródmieœcie and a ony, including also societies of honey bees nests Medical Diagnostic Laboratory “Analityk” for help in the implementation of microbiological studies as well as which are more and more often recorded in urban thanks the municipal and forest services and especially the structures (Nadolski 2008). Regional Fire Brigade Headquarters for the long-term co- The main enemy of wasp societies in the city operation. 214 Nadolski • ENTOMOL. FENNICA Vol. 24

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