Cryptocephalus rufipes (Goeze, 1777)

Schöller, Matthias, 2014, Cryptocephaline Egg Case Provides Incomplete Protection from Generalist Predators (Coleoptera: Chrysomelidae), Psyche: A Journal of Entomology (176539) 2014, pp. 1-4 : 2

3.1. Field Observations. Beside C. rufipes , several other Chrysomelidae were occurring on Salix purpurea in June and July, namely Cryptocephalus (Burlinius) ocellatus ocellatus Drapiez, 1819 , C. androgyne Marseul, 1857 , Phratora vitellinae (Linnaeus, 1758) , and Clytra laeviuscula (Ratzeburg, 1837) . Moreover, the weevil Polydrusus (Polydrusus) picus (Fabricius, 1792) was found feeding and mating on S. purpurea .

3.2. Morphology of C. rufipes Eggs. The eggs of C. rufipes are blackish to greyish brown with eight narrow, regular ridges as illustrated in Figure 1 . Each individual faecal plate bears a little crest; the regular arrangement of the faecal plates composes the ridges that have little gaps in case the faecal plates do not perfectly touch. The mean size ± SD was 0.797 mm ± 0.057 mm length and 0.532 mm ± 0.033 mm width; median was 0.80 for length and 0.53 for width. Length was ranging from 0.700 to 0.975 mm, width from 0.475 to 0.600 mm. The eggs are elongate oval; the mean length to width ratio was 1.50 mm ± 0.095, ranging from 1.25 to 1.70 (median 1.50).

3.3. Experiments with Eggs of E. kuehniella . The experiments with eggs of E. kuehniella resulted in complete predation of these eggs by both C. carnea and X. flavipes . In the untreated control, 92% of the E. kuehniella- eggs emerged.

3.4. Experiments with Eggs of C. rufipes, Behavioural Observations. When encountering the C. rufipes eggs, the larvae of C. carnea showed the typical prey uplifting behaviour. They fixed the C. rufipes eggs and held them in position ( Figure 2 ). X. flavipes examined the eggs after contacting it ( Figure 3 ). Within the first three days of the experiment, in all trials one predator consumed the second; consequently, cannibalism occurred.

3.5. Experiments with Eggs of C. rufipes, Larval Hatch. Larvae hatched after 10 to 13 days. The presence of the predators significantly affected the number of hatching C. rufipes - larvae from the eggs (Kruskal-Wallis One Way Analysis of Variance on Ranks, 𝐻 = 18.473, DF = 2, 𝑃 <0.001). In the untreated control, a mean ± SD of 3.23±1.02 larvae hatched. The presence of both C. carnea and X. flavipes significantly reduced the number of hatching C. rufipes -eggs (All Pairwise Multiple Comparison Procedures, Dunn’s Method, 𝑄 = 3.891 and 2.817, 𝑃 <0.05). A mean of 0.91±1.38 and 1.55± 1.29 hatched in the presence of C. carnea and X. flavipes , respectively. However, there was no statistical difference in reduction between the two predators (Dunn’s Method, 𝑄 = 0.929, 𝑃>0.05) ( Figure 4 ).

Figures

FIGURE 1: Egg of Cryptocephalus rufipes (Goeze, 1777), scale = 0.5 mm.

FIGURE 2: Larva of Chrysoperla carnea (Stephens, 1836) uplifting an egg of Cryptocephalus rufipes (Goeze, 1777).

FIGURE 3: Adult of Xylocoris flavipes (Reuter, 1875) handling an egg of Cryptocephalus rufipes (Goeze, 1777).

FIGURE 4: Number of Cryptocephalus rufipes-larvae hatched out of five eggs exposed to Chrysoperla carnea or Xylocoris flavipes, or no predators (untreated). Means followed by the same lowercase letter do not differ significantly at 𝑃<0.05 (Dunn’s Method) (𝑛=11).