Benefits and Costs of Mixed-Species Aggregations in Harvestmen (Arachnida: Opiliones)

Many animals form aggregations with individuals of the same species (single-species aggregations, SSA). Less frequently, individuals may also aggregate with individuals of other species (mixed-species aggregations, MSA). Although the benefits and costs of SSA have been intensively studied, the same is not true for MSA. Here, we first review the cases of MSA in harvestmen, an arachnid order in which the records of MSA are more frequent than other arthropod orders. We then propose several benefits and costs of MSA in harvestmen, and contrast them with those of SSA. Second, using field-gathered data we describe gregariousness in seven species of Prionostemma harvestmen from Costa Rica. These species form MSA, but individuals are also found solitarily or in SSA. We tested one possible benefit and one possible cost of gregariousness in Prionostemma harvestmen. Regarding the benefit, we hypothesized that individuals missing legs would be more exposed to predation than eight-legged individuals and thus they should be found preferentially in aggregations, where they would be more protected from predators. Our data, however, do not support this hypothesis. Regarding the cost, we hypothesized that gregariousness increases the chances of parasitism. We found no support for this hypothesis either because both mite prevalence and infestation intensity did not differ between solitary or aggregated individuals. Additionally, the type of aggregation (SSA or MSA) was not associated with the benefit or the cost we explored. This lack of effect may be explained by the fluid membership of the aggregations, as we found high turnover over time in the number of individuals and species composition of the aggregations. In conclusion, we hope our review and empirical data stimulate further studies on MSA, which remains one of the most elusive forms of group living in animals.

Endoparasitic Mites (Rhinonyssidae) on Urban Pigeons and Doves: Updating Morphological and Epidemiological Information

Rhynonyssidae is a family of endoparasitic hematophagous mites, which are still largely unknown even though they could act as vector or reservoir of different pathogens like dermanyssids. Sampling requirements have prevented deeper analysis. Rhinonyssids have been explored in a few host specimens per species, leading to undetailed morphological descriptions and inaccurate epidemiology. We explore the relationships established between these parasites in two Columbiformes urban birds (domestic pigeon (Columba livia domestica) and Eurasian collared dove (Streptopelia decaocto)), assesing 250 individuals of each type in Seville (Spain). As expected, Mesonyssus melloi (Castro, 1948) and Mesonyssus columbae (Crossley, 1950) were found in domestic pigeons, and Mesonyssus streptopeliae (Fain, 1962) in Eurasian collared doves. However, M. columbae was found for the first time in Eurasian collared doves. This relationship could be common in nature, but sampling methodology or host switching could also account for this result. An additional unknown specimen was found in a Eurasian collared dove, which could be a new species or an aberrant individual. We also provide an epidemiological survey of the three mite species, with M. melloi being the most common one followed by M. streptopeliae and M. columbae. High variation between previous epidemiological measurements and ours highlights the importance of developing deeper studies to uncover the factors regulating mite prevalence and intensities of infection.

Seasonal Changes in Size and Mite-Prevalence of a Bee Colony Exposed to Dinotefuran via Pollen Paste and Damaged by Varroa Mites

Neonicotinoids, such as dinotefuran (DF), have caused a variety of problems, such as massive loss and winter failure of the bee colony, as a price for the benefit of reducing farm work, because it continues to maintain a high insecticide activity over a long period of time. In this study, a field experiment was conducted for about six months to investigate the effects of DF on bee colonies damaged by Varroa mites. This study examined the long-term changes in such as the size of bee colonies, the intake of sugar syrup (SS), intake of pollen paste (PP), which is a vehicle for administering DF, the intake of DF, the mite-prevalence of bees and the inside and outside temperatures of hive-boxes. The variation width of the inner temperature of the hive-box is less than that of the ambient temperature (Ta). The inner temperature of the hive-box is adjusted with about 30 ℃ of Ta as the boundary. If Ta is lower than 30 ℃, the inner temperature of the box is higher than Ta, and if Ta is higher than 30 ℃, it is lower than Ta. The temperature variation width of the DF-exposed colony is greater than that of the control colony. The average intake of SS per bee per day of the DF-exposed colony is more than that of the control colony. The average intake of PP per bee per day of the DF-exposed colony is almost equal to that of the control colony. These results suggest that bees do not avoid DF, and ingest PP without distinction between toxic and pesticide-free. In the period from the start of DF administration to the colony extinction, the intake of DF per colony is about 865 µg/colony, the intake per bee is 14 ng/bee, and the intake per bee per day is less than 0.1 ng/bee/day in this work. These intakes are much lower than the previous ones (60-65 ng/bee, 0.27-2.32 ng/bee/day). These discrepancies may be because attacks of mites and Japanese giant hornets hastened the colony collapse. Seasonal changes in mite-prevalence of honeybees is approximately the same regardless of the bee colonies. At the end of August (the start of attacks by Japanese giant hornets), the mite-prevalence will increase rapidly. Even if the number of bees damaged by mites turns to decrease, the mite-prevalence will continue to increase, with approaching 100% before bee colonies become extinct. In this study, it was found that the bee colony was collapsed by the intake of a smaller amount of DF due to the synergistic effect of DF and mite-damage. To prevent a bee colony collapse, not only to make an effort to minimalize the adverse effect on the bee colony of neonicotinoids such as DF with long-term residual effect and high insecticide properties, it is necessary to reduce the damage of mites as much as possible, while considering the synergistically adverse effects of neonicotinoids and miticides.

Large males have fewer water mites (Arrenurus sp.) on the variable bluet (Coenagrion pulchellum) damselfly

Ectoparasitic water mites of the genus Arrenurus Dugès, 1834 may affect damselflies in different ways, resulting in lower longevity and reproduction success. We studied the variation of water mite occurrence on the variable bluet (Coenagrion pulchellum (Vander Linden, 1823)) damselfly in relation to the host’s sex, location, and wing length, as well as the amount of black pigment on the abdomens of males. In our study, we found that water mite prevalence and abundance were higher on females. Location of the populations did not affect the prevalence of water mites, nor did the colouring of males. The prevalence and abundance of water mites was lower on larger males than on smaller ones. Our results suggest that females are likely to have more water mites due to different behaviour and life-history strategies. According to our results, male body size is a sign of good condition and, thus, of sufficient resources available to be directed to strengthening their immune systems.

Communities of gamasid mites on Eothenomys miletus in southwest China

The Yunnan red-backed vole (Eothenomys miletus) is an endemic and specific wild rodent species in China. From 39 sites across southwest China, a total of 12,536 individuals of gamasid mites were collected from 2,463 voles between 2001 and 2013. The 12,536 mites were identified as comprising 106 species, 26 genera and 9 families. The overall mite prevalence and mean abundance from all the voles were 48.36% and 5.09 mites/per examined vole, respectively. Laelaps chini (C

Studies of the honey bee tracheal mite (Acarapis woodi) (Acari: Tarsonemidae) during winter

Changes in the populations of tracheal mites (Acarapis woodi) in individual honey bees were quantified in New York during winter. Mite prevalence increased greatly from November to February, then declined again in late spring. The simultaneous increases in prevalence values and in slight infestations restricted to the outer portions of the tracheae strongly suggest that many older bees were becoming infested with mites during the winter period when no brood was being reared. Trends in mite infestations varied greatly in different colonies for reasons that are not clear. Although mite reproduction was generally low (< 2.5 immatures per female), it appeared to be higher in October than during the rest of the winter. The sex ratio (3.04) was biased in favour of females. These patterns are different in some respects from those described for the same organism in Europe, emphasizing the need to carefully evaluate the biology of tracheal mites in North America and their interactions with their bee hosts before predicting their economic impact.