This dataset comes from an experiment investigating factors affecting predation by the Harlequin ladybird. Individual ladybirds of known sex (Sex: Female, Male) were introduced into Petri dishes, each containing six prey items—either pea aphids or lacewing larvae (Prey: Aphid, Lacewing). The experiment followed a randomized complete block design with four treatment combinations arranged across 15 rows (blocks), resulting in 60 observations. On each occasion, one ladybird was observed for the number of prey (Eaten) consumed in 60 minutes. Rows 1–15 combine replicates from both multiple occasions and multiple blocks, enabling the analysis of treatment effects while accounting for replicate variation. The data allow for examination of the influence of ladybird sex and prey type on short-term predation rates, with the outcome variable assumed to follow a Binomial distribution.
Format
A data frame with 7 variables: ID, Row, Dish, Sex, Prey, Eaten, Total.
- ID
Factor. Unique identifier for each observation (Petri dish).
- Row
Factor. Block or replicate identifier (1 to 15), combining experimental occasions and spatial replicates.
- Dish
Factor. Dish number within each row/block (1 to 4, one for each treatment combination).
- Sex
Factor. Sex of the Harlequin ladybird ("Female" or "Male") in the dish.
- Prey
Factor. Prey type offered: "Aphid" or "Lacewing".
- Eaten
Integer. Number of prey consumed by the ladybird in 60 minutes.
- Total
Integer. Total number of prey items offered in the dish (always 6).
Source
Welham, S. J., Gezan, S. A., Clark, S. J., and Mead, A. (2015) Statistical Methods in Biology: Design and analysis of experiments and regression
Examples
glm(cbind(Eaten, Total) ~ Row + Sex * Prey, family = binomial(), data = prey)
#>
#> Call: glm(formula = cbind(Eaten, Total) ~ Row + Sex * Prey, family = binomial(),
#> data = prey)
#>
#> Coefficients:
#> (Intercept) Row2 Row3
#> -0.30284 -0.07943 -1.23394
#> Row4 Row5 Row6
#> -0.20371 -0.29386 -0.62670
#> Row7 Row8 Row9
#> -0.19660 0.36441 -1.55313
#> Row10 Row11 Row12
#> -0.96105 -0.92139 -0.31748
#> Row13 Row14 Row15
#> -1.62318 -0.14130 -1.21291
#> SexMale PreyLacewing SexMale:PreyLacewing
#> -1.13843 -0.42833 0.09693
#>
#> Degrees of Freedom: 59 Total (i.e. Null); 42 Residual
#> Null Deviance: 87.3
#> Residual Deviance: 46.48 AIC: 173.7