Research Article |
Corresponding author: Atte Komonen ( atte.komonen@jyu.fi ) Academic editor: Volker Lohrmann
© 2023 Atte Komonen.
This is an open access article distributed under the terms of the Creative Commons Attribution License (CC BY 4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
Citation:
Komonen A (2023) Nest characteristics and associates of Dolichovespula (Hymenoptera, Vespidae) in Central Finland. Journal of Hymenoptera Research 96: 45-55. https://doi.org/10.3897/jhr.96.98238
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In social vespine wasps, the nest characteristics and associates vary intra- and interspecifically. I studied the nest characteristics and nest associates of three Dolichovespula wasp species in boreal Finland. The average number of combs and cells per nest was similar among D. media, D. saxonica and D. norwegica, and similar to Dolichovespula in the temperate zone. Most D. media and D. saxonica colonies produced both gynes and males, whereas D. norwegica produced mainly either one. The average colony lifespan of D. saxonica was a bit over two months, i.e. shorter than documented for Dolichovespula in the temperate zone. The proportion of nests parasitised by the ichneumonid wasp Sphecophaga vesparum was 36% in D. saxonica and 50% in D. media; S. vesparum has not been recorded from D. media before. The proportion of parasitized cells was 0.6–11% for D. saxonica and 0.2–22% for D. media. The proportion yellow, overwintering cocoons of S. vesparum was highly variable among the nests. The proportion of nests parasitised by the moth Aphomia sociella was 36% in D. saxonica and 13% in D. media. Sphecophaga and Aphomia were not recorded from D. norwegica colonies, which supports studies in the temperate zone. The study adds up to the previous research on the nest structure and nest associates of vespines, and together they indicate that there is geographical variation within Europe and globally in the host use of Sphecophaga.
Aphomia sociella, colony structure, social wasps, Sphecophaga vesparum, Vespinae
Social vespine wasps (Vespinae) are divided in four to five genera (
In Finland, cuckoo wasps Dolichovespula adulterina (Du Buysson, 1905) and D. omissa (Bischoff, 1931) parasitize D. saxonica (Fabricius, 1793) and D. sylvestris (Scopoli, 1763), respectively (
The nest characteristics and associates of Dolichovespula are poorly studied in comparison with Vespula, especially in the boreal region. The extant studies have been conducted in very different geographical locations and suggest geographical variation in the biology of Dolichovespula (e.g. US,
The study was conducted in the province of Central Finland, which belongs to the middle boreal zone. During 2019–2022 Dolichovespula nests were located based on public information and active searching. All nests were within 60 km (mostly within 5 km) from the Jyväskylä city centre. Nests were in a variety of natural and anthropogenic locations, mostly in semiurban broadleaved or mixed forests. Most D. saxonica nests were inside wooden bird nest boxes (1.3–2.0 m above ground) that were used for a bird study (
Lifespan was documented for seven D. saxonica colonies in bird nest boxes (n = 7), which were monitored about once a week for a bird study from April 2021 onwards. Colony lifespan was determined as the difference between the first date the wasp was observed and the date of colony removal. Because the colonies were initiated earlier than observed at the first time, I estimated the date of colony initiation: the number of days between the date a nest box was observed occupied and the previous date the nest box was empty, divided by two). At the time of removal, four colonies had just ceased and three were still active, although at their final phase with males and gynes.
To make colonies comparable they should be in the same developmental phase. This was not fully possible. Thus, in analyses I focused on the mature colonies, which were determined as having large cells containing sealed brood or large cells from which the adults had emerged (see
The number of combs and cells was variable among nests but there were no interspecific differences (H = 1.1, p = 0.57 and H = 0.7, p = 0.72, respectively, df = 2, n = 38; Table
Characteristics of the studied nests, the percent parasitized nests, the mean (min–max) percent of parasitized cells in occupied nests, and the mean (min–max) number of individuals per occupied nest.
Nest | Combs | Cells | S. vesparum | A. sociella | ||||
---|---|---|---|---|---|---|---|---|
n | Mean (SD) | Med, Mean (SD) | % nests | % cells | Exx./nest | % nests | Exx./nest | |
D. saxonica | 31 | 3.7 (1.2)* | 854, 739 (420) | 36# | 4 (0.6–11)$ | 19 (2–48)£ | 36£ | 33 (2–94)& |
D. norwegica | 4 | 4.3 (0.5) | 712, 1079 (762) | 0 | 0 | 0 | 0 | 0 |
D. media | 8 | 4.1 (0.8) | 626, 674 (275) | 50 | 11 (0.2–22) | 104 (1–256) | 13 | 1 |
The most frequent and abundant nest associates were S. vesparum and A. sociella. These attacked D. saxonica and D. media, whereas no nest associates were found in D. norwegica nests. Both in D. media and D. saxonica, S. vesparum parasitized large and small cells. In D. media, there was an average of 1.5 (max. = 8) parasitoid individuals per host cell, and in D. saxonica 1.1 (max. = 4). In both species, there was generally more yellow than white S. vesparum cocoons (Table
The number and ratio of white and yellow cocoons of S. vesparum, and the proportion of open (parasitoid emerged) white and yellow cocoons in D. media (Dm) and D. saxonica (Ds) nests.
Empty (%) | |||||
---|---|---|---|---|---|
Nest | White | Yellow | Ratio | White | Yellow |
Dm1 | 15 | 21 | 0.71 | 0.93 | 0 |
Dm2 | 25 | 231 | 0.11 | 0.76 | 0.02 |
Dm3 | 65 | 55 | 1.18 | 0.89 | 0.11 |
Dm4 | 0 | 1 | 0 | na | 0 |
Ds1 | 2 | 31 | 0.06 | 0.5 | 0.06 |
Ds2 | 10 | 21 | 0.48 | 0.9 | 0.05 |
Ds3 | 11 | 37* | 0.30 | 1 | 0.27 |
Ds4 | 4 | 1 | 4 | 0.25 | 0 |
Ds5 | 1 | 1 | 1 | 1 | 1 |
Ds6 | 0 | 2 | 0 | na | 0.5 |
Ds7 | 2 | 22 | 0.09 | 0 | 0 |
Ds8 | 0 | 7 | 0 | na | 0.86 |
The nest locations were variable. All D. norwegica nests were aerial in trees or bushes. All D. media nests were aerial in natural or anthropogenic objects. Nest locations of D. saxonica were the most variable and generally aerial. In addition to natural objects, they were found in many anthropogenic objects. The results underscore flexibility in nesting locations and ability to utilize anthropogenic locations (at least D. saxonica and D. media; see also
The studied Dolichovespula species had more similarities than differences and the colonies were of typical size for Dolichovespula (see
Most nests, especially the larger ones, had more than one comb that were dominated by small cells (usually the first and the last). Although the middle combs consisted generally of large or medium cells, mixed combs were common. These results support previous studies indicating intra- and interspecific variation in the distribution of cell sizes among combs (
The production of males and gynes varied among species. 75% of the D. media nests had both males and gynes; it is likely that also the other two colonies produced or would have produced both sexes, but in one of these nests most individuals had already left and the other was heavily parasitized. 55% of the D. saxonica colonies that had sexual castes produced both males and gynes; all the single-sex colonies produced only males. Because larvae were still present it is possible that some would have produced gynes later. It is known, however, that D. saxonica colonies usually produce more males than gynes (
The most common nest associates were S. vesparum and A. sociella, whereas no social vespine parasites were observed. Sphecophaga vesparum parasitized both D. media and D. saxonica. To my knowledge, S. vesparum has not been recorded from D. media before (see also
The nest-specific rate of parasitism was variable but generally low. Again, the average rate of parasitism was higher in D. media (11%) than in D. saxonica (4%). These figures are like, or slightly higher (D. media) than in other studies of Dolichovespula (
In general, there were more yellow than white cocoons. Yellow cocoons are those in which the adult parasitoid overwinters (
The prevalence of A. sociella was similar to S. vesparum in D. saxonica nests but lower in D. media nests. Low prevalence in D. media nests may be explained in that proportionally more nests were active when collected, because A. sociella predominantly colonize declining colonies. Aphomia sociella was not found from D. norwegica nests, and it remains unknown if the species can colonize D. norwegica nests. Although M. paradoxus has been occasionally observed from the nests of Dolichovespula in other parts of the world, no individuals were observed in this study, although the species is common in V. vulgaris nests in the study region (
To establish any pattern in biology, studies must be replicated in space and time. This study supports some earlier studies about the biology of Dolichovespula but also suggests that some issues need more studies so that their generality can be evaluated. Particularly, the variation in the host use of S. vesparum needs more research attention, which requires that different Dolichovespula species are studied in the same regions. It is also clear that observed level of parasitism cannot cause significant year-to-year variation in Dolichovespula abundance but can occasionally cause moderate damage in individual colonies. Furthermore, more studies are needed on the other Dolichovespula than D. saxonica, especially since D. norwegica has no documented nest associates.
I thank Kone foundation for a research grant to the wasp project. I thank Lauri Viitanen and Tatu Koponen for the help in the lab, and Jyrki Torniainen for the help in the field.
Nest characteristics
Data type: Nest characteristics
Explanation note: Nest locations, combs and cell numbers, and nest associates.