<p>Many prey species are able to develop different morphological structures as defence against</p><p>for example predators. Some of these structures are induced only by individuals exposed to a</p><p>predator. This phenomenon is called phenotypic plasticity. In this paper we examine whether</p><p>cuticle thickness in Leucorrhinia dubia (Odonata) larvae differed between specimens caught</p><p>in fish containing lakes and fish-free lakes respectively. We measured the thickness of the</p><p>cuticle from four different parts of the larvae; profemur, pronotum, ninth segment sternite and</p><p>ninth segment tergite. Our results showed a significantly thicker exocuticle on profemur in</p><p>larvae with a head width bigger than 4.5 mm caught in lakes with fish. The smaller larvae</p><p>showed a tendency to have thinner exocuticle on profemur in presence of fish. We discuss the</p><p>probability that the differences in exocuticle thickness on profemur could be some kind of</p><p>trade-off situation. The results also showed a tendency among the large larvae; the large</p><p>individuals from lakes containing fish had a slightly thicker exocuticle on pronotum than the</p><p>bigger individuals from fish-free lakes.</p>

Many prey species are able to develop different morphological structures as defence against for example predators. Some of these structures are induced only by individuals exposed to a predator. This phenomenon is called phenotypic plasticity. In this paper we examine whether cuticle thickness in Leucorrhinia dubia (Odonata) larvae differed between specimens caught in fish containing lakes and fish-free lakes respectively. We measured the thickness of the cuticle from four different parts of the larvae; profemur, pronotum, ninth segment sternite and ninth segment tergite. Our results showed a significantly thicker exocuticle on profemur in larvae with a head width bigger than 4.5 mm caught in lakes with fish. The smaller larvae showed a tendency to have thinner exocuticle on profemur in presence of fish. We discuss the probability that the differences in exocuticle thickness on profemur could be some kind of trade-off situation. The results also showed a tendency among the large larvae; the large individuals from lakes containing fish had a slightly thicker exocuticle on pronotum than the bigger individuals from fish-free lakes.

Forest canopies are complex and highly diverse environments. Their diversity is affected by pronounced gradients in abiotic and biotic conditions, including variation in leaf chemistry. We hypothesised that branch-localised defence induction and vertical stratification in mature oaks constitute sources of chemical variation that extend across trophic levels. To test this, we combined manipulation of plant defences, predation monitoring, food-choice trials with herbivores and sampling of herbivore assemblages. Both induction and vertical stratification affected branch chemistry, but the effect of induction was stronger. Induction increased predation in the canopy and reduced herbivory in bioassays. The effects of increased predation affected herbivore assemblages by decreasing their abundance, and indirectly, their richness. In turn, we show that there are multiple factors contributing to variation across canopies. Branch-localised induction, variation between tree individuals and predation may be the ones with particularly strong effects on diverse assemblages of insects in temperate forests.