Velia currens (Fabricius, 1794) and V. gridellii Tamanini, 1947 are two Alpine-Apenninic endemic insects, and little is known about their ecology and behaviour. A key with field identification characters was created for the subsequent ecological studies, and the analysis of several morphological features defined the species groups within the subgenus Plesiovelia Tamanini, 1955 for the first time. The two species appeared to belong to different groups. The ecological studies investigated life histories, quantified occurrence of wing polymorphism and gathered information regarding the degree of co-occurrence of the two species. No evidence for multivoltinism was detected in either species. However, oviposition and and/or hatching continued up to midsummer. The two species are dimorphic, but winged specimens were rarely recorded. An important discovery was the presence, during summer, of adults of both sexes hidden beneath the stones of dried-up streams. This aestivation in an apparent state of lethargy may reduce the advantages associated with producing winged forms and could account for the low rate of occurrence of macropterism in these species. Finally, although the distributional ranges of the two taxa completely overlap on a large spatial scale, they co-occurred only rarely at the same sites and the degree of co-occurrence was lower than expected by chance. The descriptions and SEM images of the hairy structures of the two taxa were planned as essential to the study of the “grooming behaviour”. The comparison between these two species and V. caprai Tamanini, 1947, the only other known species of the genus, comfirmed a substantial homogeneity within the subgenus Plesiovelia. The discovery of a double layer of microtrichia in both our species allowed us to detect them in V. caprai too, for which only a single layer had previously been described. Finally, we report for the first time in the genus, and in the Old World Veliinae, the presence in the females of V. gridellii of a structure corresponding to the grasping comb already described in males. A similar structure was not identified in V. currens. Considering the species groups, this difference may be relevant to a better understanding of the relationships among species belonging to this genus. The “grooming behaviour”, a series of cleaning actions performed to tidy the waterproofing hair layers throughout the body surfaces and maintain them free from debris, was described. Results showed that this behavior may be highly variable even within the same species, with some steps sometimes being skipped, suggesting that once the “pattern” has started, this action is not modulated by way of feedback from the area that has been cleaned. The behaviour is, however, extremely similar in the two species, and only a few differences were noticed such as a different number of passages over the antennae. A peculiar behaviour, observed under natural and laboratory conditions in both the species, consists in interactions (“collisions”) among the specimens and was named “contact behaviour”. Preliminary observations on Velia gridellii 4 Tamanini, 1947, through the analysis of the networks representing the contacts between specimens of this aquatic insect, did not allowed to evidence any difference between males and females, neither in their degree of connection with other specimens, nor in the role they played.

Ecology and behaviour of Velia currens and V. gridellii (Hemiptera: Heteroptera: Veliidae) / F. Cianferoni. - STAMPA. - (2012).

Ecology and behaviour of Velia currens and V. gridellii (Hemiptera: Heteroptera: Veliidae)

CIANFERONI, FABIO
2012

Abstract

Velia currens (Fabricius, 1794) and V. gridellii Tamanini, 1947 are two Alpine-Apenninic endemic insects, and little is known about their ecology and behaviour. A key with field identification characters was created for the subsequent ecological studies, and the analysis of several morphological features defined the species groups within the subgenus Plesiovelia Tamanini, 1955 for the first time. The two species appeared to belong to different groups. The ecological studies investigated life histories, quantified occurrence of wing polymorphism and gathered information regarding the degree of co-occurrence of the two species. No evidence for multivoltinism was detected in either species. However, oviposition and and/or hatching continued up to midsummer. The two species are dimorphic, but winged specimens were rarely recorded. An important discovery was the presence, during summer, of adults of both sexes hidden beneath the stones of dried-up streams. This aestivation in an apparent state of lethargy may reduce the advantages associated with producing winged forms and could account for the low rate of occurrence of macropterism in these species. Finally, although the distributional ranges of the two taxa completely overlap on a large spatial scale, they co-occurred only rarely at the same sites and the degree of co-occurrence was lower than expected by chance. The descriptions and SEM images of the hairy structures of the two taxa were planned as essential to the study of the “grooming behaviour”. The comparison between these two species and V. caprai Tamanini, 1947, the only other known species of the genus, comfirmed a substantial homogeneity within the subgenus Plesiovelia. The discovery of a double layer of microtrichia in both our species allowed us to detect them in V. caprai too, for which only a single layer had previously been described. Finally, we report for the first time in the genus, and in the Old World Veliinae, the presence in the females of V. gridellii of a structure corresponding to the grasping comb already described in males. A similar structure was not identified in V. currens. Considering the species groups, this difference may be relevant to a better understanding of the relationships among species belonging to this genus. The “grooming behaviour”, a series of cleaning actions performed to tidy the waterproofing hair layers throughout the body surfaces and maintain them free from debris, was described. Results showed that this behavior may be highly variable even within the same species, with some steps sometimes being skipped, suggesting that once the “pattern” has started, this action is not modulated by way of feedback from the area that has been cleaned. The behaviour is, however, extremely similar in the two species, and only a few differences were noticed such as a different number of passages over the antennae. A peculiar behaviour, observed under natural and laboratory conditions in both the species, consists in interactions (“collisions”) among the specimens and was named “contact behaviour”. Preliminary observations on Velia gridellii 4 Tamanini, 1947, through the analysis of the networks representing the contacts between specimens of this aquatic insect, did not allowed to evidence any difference between males and females, neither in their degree of connection with other specimens, nor in the role they played.
2012
G. Santini
F. Cianferoni
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Utilizza questo identificatore per citare o creare un link a questa risorsa: https://hdl.handle.net/2158/797453
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