# Body Size of Female Strepsipteran Parasites (Strepsiptera, Xenidae, Xenos) Depends on Several Key Factors in a Vespine Wasp (Hymenoptera, Vespidae, Vespa)

## TL;DR

The body size of female strepsipteran parasites is influenced by host wasp size, parasite numbers per host, and the host's reproductive status.

## Contribution

This study identifies key factors influencing parasite body size in a specific wasp-host system.

## Key findings

- Female parasite body size is positively correlated with host wasp size.
- More parasites per host lead to smaller female parasite body sizes.
- Female parasites are larger when host queens have less-developed ovaries.

## Abstract

We studied whether the female body size of strepsipteran parasites of Xenos oxyodontes is affected by the following four factors: season, host body size, multiparasitism, and reproductive conditions of the host wasp. The cephalothorax width of female parasites did not change throughout the seasons but was strongly affected by host body size, number of parasites per host wasp, and reproductive conditions of host wasps. Our results suggested that female parasites with larger body sizes have greater potential for reproduction.

Parasite growth in hosts depends on their hosts’ nutritional status. This study examined whether the body size of the strepsipteran parasite Xenos oxyodontes, which parasitizes the eusocial wasp Vespa analis, is affected by several key factors, including host body size. We collected V. analis using bait traps for three years in Niigata, Japan, and evaluated the number of male and female X. oxyodontes parasites throughout the seasons. A total of 185 female parasites were collected, and their cephalothorax widths were measured. The widths of female parasites did not statistically vary among seasons and were positively correlated with the head widths of female host wasps but negatively correlated with the number of parasites per host wasp. In addition, we examined whether the reproductive conditions of post-hibernation solitary queens affected the cephalothorax width of female parasites. The widths of the female parasites were greater when the queens had less-developed ovaries. These results suggested that nutrient availability by female parasites depends on the host wasp and competition with conspecific individuals.