Figure 4.
Comparison of mosquito abundance within hibernacles of alkaline and acidic surrounding rock combined with humidity levels. Statistical significance is symbolized with A, B and C, where non-matching letters are significantly different (Chi Square: 61.9, 22 df, p = 0.0002; corrected min./max. value A against B: p = 0.0004/0.0016). Y-Axis: composition of categories within the sampling. The numbers in the bar graphs show the absolute frequency of categories in the respective years. Categories: many: > 20 individuals, several: 10–20 individuals, few: 1–10 individuals found within the subterranean shelter.