Male competition for females can often take the form of direct physical contests. The outcome of a given contest or the decision to persist is determined by the resource holding potential (RHP) of rivals, which often corresponds to body size or weapon size. Males of the endemic New Zealand sheet-web spider Cambridgea plagiata Forster & Wilton 1973 have exaggerated chelicerae that are used in contests to gain access to females. We staged male–male contests in the field to determine the factors contributing to contest duration and outcome. The current models which describe how individuals make decisions to persist in a contest fall broadly into (i) energetic war of attrition or pure self-assessment, (ii) mutual assessment, and (iii) cumulative assessment. Our results showed that male body size was the key predictor in determining the winner of a given contest. The durations of contests were more consistent with predictions from either mutual or cumulative assessment models. We highlight that staging contests in the field may result in more realistic results and natural behaviours. Similar to the congener C. foliata, it appears that further development of current contest models may be required to understand male contests in sheet-web spiders.

The armoured scale insect Oceanaspidiotus spinosus (Comstock 1883) (Hemiptera: Diaspididae) was found on kiwifruit from the Bay of Plenty in April 2019. This is the first record from New Zealand. Subsequent surveys have confirmed O. spinosus at multiple locations in the Bay of Plenty and Gisborne regions and it is now considered to be established. Previously, only three armoured scale species: Hemiberlesia lataniae, Hemiberlesia rapax and Aspidiotus nerii, have been found on kiwifruit in New Zealand. Reliable identification of these species and O. spinosus requires slide mounting and microscopic examination of adult female specimens. Oceanaspidiotus spinosus is a cosmopolitan species recorded in 51 countries and island states. It is highly polyphagous and has been found on many host plants including kiwifruit, avocado, citrus, apple, persimmon, grape and blueberry. Although O. spinosus is not reported to be a major pest of these hosts, it may have market access implications for exported crops.

We investigate key ecological differences and track population dynamics in two sympatric species of sheet-web spider, Cambridgea plagiata and Cambridgea foliata throughout a single breeding season. We undertook a series of weekly population surveys in plots that included both C. plagiata and C. foliata, recording features of their web ecology and of each species' population dynamics over a single breeding season. We found significant differences in the distribution, web size and substrate, and predominant diet of C. plagiata and C. foliata with the former feeding predominantly on amphipods, building smaller webs and associating with rock walls, resulting in areas of densely aggregated webs. By contrast, moths were the predominant prey type found in C. foliata webs which were larger and more common in open vegetation, resulting in a more uniform distribution of webs within our plots. Additionally, both species exhibit pre-copulatory guarding consistent with the expectations of a first-male sperm priority pattern, suggesting male competition over virgin females. This is despite a consistent female-biased sex ratio. This research not only provides the first ecological data for C. plagiata and C. foliata but provides important context for sexually selected behaviours performed by males in these species.

Sexual selection has repeatedly driven the evolution of exaggerated secondary sexual traits in male animals. When multiple traits are used in competitive contexts, producing or bearing one trait may be costly and come at the expense of other traits via trade-offs. Conversely, sexually selected traits may show positively correlated patterns of relative investment. Males of the sheetweb spider, Cambridgea plagiata, have exaggerated chelicerae and use their chelicerae and forelegs in male-male contest behaviour. In the present study, we describe the linear scaling relationship of the chelicerae and forelegs of both males and females. Chelicerae length was positively allometric for males, but not for females, whereas fore-tibiae and fore-femora showed a slightly negative allometric relationship for both sexes. We found no evidence of a trade-off between the length of tibiae and femora with chelicerae length when comparing simple phenotypic correlations. Rather, the length of the tibia and femur, relative to body size, both increased when compared with relative chelicerae length, indicating that these traits might be under correlational selection. This suggests that larger chelicerae and forelegs are advantageous to males and that when resources are available, males will invest in both these traits.