Systematics and community composition of foraging worker ants (Family: Formicidae) collected from three habitats in a dry zone region of Sri Lanka

Abstract

Ants (Order: Hymenoptera, Family: Formicidae) are an important and common biotic component in the wet zone of Sri Lanka. Eleven subfamilies, 57 genera and 123 morphospecies of ants have been recorded from the wet zone recently, but little is known about the ants that inhabit dry zone of Sri Lanka. A survey on the dry zone worker ants was carried out from 2"d to 3'd of November, 2007 in three types of habitats, a forest, Kahalla - Pallekele forest (N 08° 311 and E 080° 301), a bitter gourd cultivation (N 07° 511 and E 080° 3 71) and in an uncultivated land (N 07° 511 and E 080° 3 71) in Dam bulla by soil sifting, litter sifting, honey baiting and pitfall trapping along 'five transects laid in each of them. A 100 m transect was laid in the forest whereas a 50m transect was laid in the other two habitats due to the smaller area of the two lands. Soil sifting and litter sifting were carried out at 5 m distance along each transect. Ten honey baits were placed at 5 m intervals along each transect and the baits were collected after an hour. Tw enty, honey-baited pitfall traps were fixed randomly in the sampling area of each habitat and the traps were collected after five hours. All samples were preserved in 85% ethanol in the field. Worker ants were sorted and identified to the furthest possible taxonomic levels in the laboratory. Air (27 °C- 32 °C) and soil temperatures (27 °C- 33 °C) and soil moisture content (8.6% - 14.5%) of each habitat were also measured. Worker ants belonging to five subfamilies, Dolichoderinae, Formicinae, Myrmicinae, Ponerinae and Pseudomyrmecinae and, 4 1 species and morphospecies of ants were recorded from the three habitats. The dolichoderines, Tapinoma indicum, Tapinoma melanocephalum, Technomyrmex albipes, the formicines, Anoplolepis gracilipes, Camponotus sp. 1, Camponotus sp. 2, Camponotus sp. 3, Camponotus sp. 4, Oeco'f.hylla smaragdina, Paratrechina longicornis, Polyrhachis sp. 1, Pseudolasius sp. , the myrm1cines, Calyptomyrmex sp. 1, Crematogaster sp. 1, Crematogaster sp. 2, Lophomyrmex sp. 1, Meranoplus bicolor, Monomorium destructor, Monomorium sp. 1, Pheidole sp. 1, Pheidole sp. 2, Pheidole sp. 3, Pheidole sp. 4, Pheidole sp. 5, Pheidole sp. 6, Solenopsis geminata, Solenopsis sp. 1, Strumigenys sp. 1, Tetramorium sp. 1, Tetramorium sp. 2, Tetramorium sp. 3, Tetramorium sp. 4, Tetramorium sp. 5, Tetramorium sp. 6, Tetramorium sp. 7, the ponerines, Anochetus sp. 1, Hypoponera sp. 1, Pachycondyla sp. 1, Platythyrea sp. 1 and the pseudomyrmecines, Tetraponera allaborans and Tetraponera rufonigra were observed in these three types of habitats. Tapinoma melanocephalum, Anoplolepis gracilipes, Paratrechina longicornis, Crematogaster sp. 1, Solenopsis geminata, Tetramorium sp. 1, Tetramorium sp. 3 and Tetramorium sp. 7 were observed m considerable proportions whereas others were found in less than 4% proportions. Significant differences were observed among the frequencies of ant species recorded in this study (Chi-square test; p< 0.05) and, Tetramorium sp. 7 (28%), Tetramorium sp. 3 ( 13.4%) and Solenopsis geminata ( 10.9%), were the dominant species observed in Dambulla region. The ponerines were observed in the forest and the uncultivated land but they were not observed in the bitter gourd cultivation. The pseudomyrmecines were not observed in the uncultivated land. Tapinoma melanocephalum, Paratrechina longicornis, Crematogaster sp.l, Meranoplus bicolor, Monomorium destructor, Pheidole sp. 1, Tetramorium sp. 1, Tetramorium sp. 3 and Tetramorium sp. 4 were common to these sites. W hen compared with the prevwus record on dry zone ants, the presence of two pseudomyrmecines is a new observation and the absence of aenictines in current habitats was also noticeable.