A REPORT ON THE OCCURRENCE OF THE SEA SKATER , HALOBATES GALATEA HERRING ( INSECTA : HEMIPTERA : GERRIDAE ) IN A MANGROVE HABITAT AT DHARMADAM , KANNUR DISTRICT , KERALA

The Sea skater Halobates galatea Herring (Insecta : Hemiptera : Gerridae) was described in 1961 by Herring based on the material procured from an unspecified locality somewhere along the west coast of India. The allotype of the species designated by Herring (1961), collected from Mumbai, India, according to Andersen and Foster (1992) belongs to H. formidabilis (Distant) and not H. galatea Herring. Based on the material collected at Chorao Island, near Paniji, Goa, India, Andersen and Foster Ope cit. redefined and redescribed H. galatea Herring. The specimens studied by them were collected from the surface of channels and pools amongst mangroves (Rhizophora) close to the shore.


INTRODUCTION
The Sea skater Halobates galatea Herring (Insecta : Hemiptera : Gerridae) was described in 1961 by Herring based on the material procured from an unspecified locality somewhere along the west coast of India.The allotype of the species designated by Herring (1961), collected from Mumbai, India, according to Andersen and Foster (1992) belongs to H. formidabilis (Distant) and not H. galatea Herring.Based on the material collected at Chorao Island, near Paniji, Goa, India, Andersen and Foster Ope cit.redefined and redescribed H. galatea Herring.The specimens studied by them were collected from the surface of channels and pools amongst mangroves (Rhizophora) close to the shore.
During a recent faunistic survey in the Kannur district of Kerala, 7 specimens of H. galatea (Plate-I) were collected from a group of 18 specimens observed in a mangrove habitat at Dharmadam, the details of which are presented below.In addition, a check-list of the species of Halobates Eschscholtz known so far from the Indian marine hab~tats is also provided.
Diagnosis: Body blackish with grayish pubescence and yellow markings; head with 2 triangular yellow markings meeting in the midline; ventral part of body in male with yellow markings, not extensive but conspicuous; lateral margin of proctiger of male roundly produced but not pointed; right styliform process curved outward; in female, the yellow colouration on the ventral part of body more extensive than in male.
Distribution : Arabian Sea along the west coast of India at Chorao Island, near Paniji, Goa; Dharmadam, Kannur district, Kerala (Present record).
Habitat: The present collection has been made from the surface of high tide waters amongst the aerial roots (Pneumatophores) of the mangrove plants, Avicennia officianalis, A. marina and Sonneratia alba.
A checklist of the species of Halobates Eschscholtz reported from India

DISCUSSION
Sea skaters of the genus Halobates Eschscholtz comprise the only known true oceanic insects.The genus comprises of 43 species, of which 5 are distributed in all tropical oceans and the remaining 38 have been recorded from the near-shore, sheltered coastal waters of the tropical Indo-Pacific (Andersen and Foster, 1992) The present report forms the first record of Halobates galatea from the coastal waters of Kerala.It further confirms the observation made by Andersen and Foster (1992) that H. galatea inhabits near-shore mangrove habitats.Besides, a recent report on the distribution of Halobates in the open oceans around India (Pathak et al., 1998) does not include H. galatea, a pointer to the fact that the species in all probability is not an open ocean inhabitant.
. Of these, 9 species viz., Halobates galatea Herring, H. jlaviventris Eschscholtz, H. formidabilis (Distant), H. elephanta Andersen & Foster, H. germanus White, H. hayanus White, H. proavus White, H. trynae Herring and H. micans Eschscholtz are known to occur in the Indian marine habitats.But for H. german us and H. micans which are open ocean species, the remaining species of Halobates known from India are apparently near-shore species preferring habitats that are sheltered from winds and wave action.