Tettigoniidae (Orthoptera) ovipositing in old galls of Dryocosmus kuriphilus (Hymenoptera: Cynipidae)

This paper presents biological notes on two species of Orthoptera: Tettigoniidae that emerged from old spongy-woody galls of Dryocosmus kuriphilus Yasumatsu, 1951 collected in Sicily (Italy) in April 2015: Leptophyes sicula Kleukers, Odé et Fontana, 2010 (Phaneropterinae) and Cyrtaspis scutata (Charpentier, 1825) (Meconematinae). Between the end of April and the fi rst few days of May a total of 30 neanids emerged from the galls, were reared and their life-cycle recorded. While L. sicula laid eggs in groups, C. scutata laid single eggs inside the galls; both species in a few years have adapted to exploiting this new shelter for egg laying. No interaction with the gall inducing insect was noted.


INTRODUCTION
Galls are induced by physical-chemical interactions between plants and organisms, such as insects, mites, nematodes, fungi, bacteria and viruses (Sugiura & Yamazaki, 2009). Galls are adaptive in that they provide the inducers with nutritious tissues and sometimes shelter from natural enemies (Price et al., 1987). Gallinducers are referred to as "ecosystem engineers" because the physical-chemical alterations they induce in plant organs in the form of galls are habitats or resources for other organisms (Sugiura & Yamazaki, 2009). Galls indeed are important resources not only for the gall-inducers, but also for other organisms, generally classifi ed as either: parasitoids, hyperparasitoids, inquilines, cecidophages, predators, successors or symbionts (Sugiura & Yamazaki, 2009).
As there are few publications on this sort of association involving grasshoppers this paper presents a description of the life cycles of two species of Orthoptera that were recorded emerging from old galls of D. kuriphilus.  All the specimens were examined under a Wild-Heerbrugg M8 stereomicroscope. Some specimens (both galls and insects) were photographed using a Canon 7D digital camera provided with a macro lens Canon MP-E 65 mm and photographs were integrated using the freeware CombineZP (Hadley, 2011). In addition, we measured the length and breadth of the ovipositor of Orthoptera that emerged from galls, using specimens preserved in museum collections. Measurements were taken using the soft- ware Optika Vision Pro. Samples are preserved in the collections of the Department of Agriculture and Forest Sciences, University of Palermo.

RESULTS AND DISCUSSION
The insects that emerged from the galls were mainly Coleoptera Anobiidae of the genus Dryophilus Chevrolat, 1832; in addition, ca. 30 neanids of Orthoptera Ensifera belonging to two species emerged between the 27th April and 2nd May 2015.
One of them was Leptophyes sicula Kleukers, Odé et Fontana, 2010 (Tettigoniidae: Phaneropterinae). The adult laid groups of eggs in crevices inside the gall (Fig. 1F). The neanid emerged from an opening in the side of an egg (Fig. 1F). The fi rst adults (male and female) emerged on 26.v.2015, one month after hatching and after an unknown number of moults (only three recorded, which occurred on 14.v.2015, 28.v.2015 and 12.vi.2015, respectively, during the night). It was diffi cult to recover their exuviae as these are eaten by the insects. During these nocturnal moults the insects were suspended from the top cover of the container; moulting lasted between 30 and 40 min.
Upon reaching maturity, they mated and the female laid eggs on the cotton wool attached to the lid of the container ( Fig.  1G and H). While these fl at eggs were elliptical in shape, were brown-amber colour, measured 3.5 × 1.9 mm, and resulted to be very fl at (0.2 mm) ( Fig. 1I and J), those found inside the galls of D. kuriphilus were clearer and not so fl at (0.7 mm) ( Fig. 1K and L), probably due to the growth of the embryo. Eggs inside galls cannot be seen from outside, so it was necessary to open the galls. Fig. 2 shows some nymphal instars of this insect, whose diagnostic characteristics are small black spots all over the body; in the fi rst instar these spots are few and there are some markings in one or two lines on each tergite ( Fig. 2A and B), later the markings are smaller and closer. Males and females of L. sicula reared in the same containers did not eat or attack one another. This is a phytophagous species, endemic to Sicily and discovered only recently (Kleukers et al., 2010), but previously considered as L. punctatissima (Bosc, 1791), a widespread European species associated with broadleaved trees and small bushes. It has a springsummer phenology (Massa et al., 2012).
The other species that emerged from eggs laid inside galls of D. kuriphilus was Cyrtaspis scutata (Charpentier, 1825) (Tettigoniidae: Meconematinae). It laid single eggs that occupied the entire empty larval chamber of the Cynipid (Fig. 1N and Q). Eggs are elliptical, light brown with a fi nely reticulated surface ( Fig. 1R and S), they measure 3 × 1.5 mm and are 0.8 mm deep. In this case, the presence of eggs inside a gall is indicated by the presence of silken remains protruding from the external wall of the gall (Figs 1M, 1N and 1P). The fi rst-instar nymph emerges from a hole in the egg next to the wall of the gall and as a result the margins of the egg shell curve outwards (Fig. 1P).
We recorded only one moult on 9.vii.2015, probably due to the small size of the insect. The fi rst adult emerged on 8.viii.2015. Fig. 3 shows some of the instars of C. scutata, whose diagnostic characteristic is a small black marking on the outside of the proximal part of its tibiae, well visible against the green coloured body (Fig. 3A-C). In Italy C. scutata is a common species with a summer-autumn phenology and over winters as an adult. Oddly, this apterous species removes its faeces by using it's hind legs to push them away. This behaviour is regularly observed in fl ightless Orthoptera Pamphagidae (pers. obs.).
C. scutata is insectivorous, probably specializing on small parasitic insects living on plants (Massa et al., 2012). We were able to confi rm that C. scutata feeds on larvae and adults of small moths, immobilizing them with the help of the spines on its forelegs. It consumes entire larvae except for the cephalic capsule. It did not feed on the Hymenoptera, including the Cynipidae provided, probably due to their hard cuticle.

CONCLUDING REMARKS
The presence in Sicily of accidentally imported D. kuriphilus was confi rmed for the fi rst time in May 2010 in some chestnut woods on Mt. Etna (Longo & Sidoti, 2011;EPPO, 2011); later it spread to other areas in Sicily (province of Messina) (Cerasa, 2015). It is likely that the species of Orthoptera and Coleoptera we recorded as successors inside galls of D. kuriphilus probably previously used other species of autochthonous galls of Cynipidae and found the galls of D. kuriphilus suitable for egg laying or over-wintering. We presume that it also lays eggs in other oak galls belonging to the subgenus Quercus, sections Quercus and Cerris, like Andricus kollari, Andricus coriarius and Synophrus politus Hartig 1843, which are rather common and suitable for the egg laying of bush-crickets. In a matter of a few years an insect community of successors has successfully colonized galls of newly arrived species in chestnut woods. However, the exploitation of the gall by successors does not cause any damage to the gall-inducer, because the galls exploited are old and gall-inducers have already emerged. Thus, egg-laying inside galls by the two species of Orthoptera reported here should not affect the spread of D. kuriphilus. We can also exclude the possibility of C. scutata being a predator of Cynipidae and a biocontrol agent of the non-native species, D. kuriphilus. In addition, other successors are saprophagous or detritivorous and do not adversely affect the biological cycle of D. kuriphilus.