Antennal and Foreleg Morphology of Solenopsis geminata (Fabricius, 1804), (Hymenoptera: Formicidae) from Tamil Nadu, India: A Morphological Contribution to Chemical Ecology

Abstract

Background: Morphological variation between major and minor workers of the tropical fire ant Solenopsis geminata provides a basis for species identification and for considering antenna-associated chemical communication. Aim: This study aims to illustrate the antennal and foreleg structures of the fire ant species Solenopsis geminata. Methodology: Ant specimens were collected from Abishekapatti between January and March 2026 (Latitude 8° 7679 N and Longitude 77° 6439 E), Tamil Nadu, India. The antennae and forelegs were dissected from ants preserved in 4% formalin and labelled in plastic vials. Diagrammatic sketches were prepared using a camera lucida mounted on an Olympus trinocular microscope (Model: CH20i). The names of the venom components were obtained from published research articles, and their structures were drawn using ChemDraw software version 23. Results: Solenopsis geminata was identified from Abishekapatti, Tamil Nadu, India. The antennae and forelegs were illustrated from worker specimens. The antenna has a total of 10 segments, including a two-segmented antennal club, erect hairs and a reddish-brown colour; the foreleg is reddish-brown and has four tarsal segments. Scape lengths were 0.30 – 0.60 mm in minor workers and 0.30 – 0.50 mm in major workers; the corresponding scape indices were 50 – 90 and 30 -50, respectively. Femur length, width and the femur index (15 -25) were calculated. Structures of six dominant alkaloid venom components reported for three Solenopsis species, together with three newly reported compounds from Solenopsis geminata, were drawn. Recent studies on fire ants indicate that OBPs are associated with olfactory processes and that cuticular hydrocarbon profiles may vary among S. geminata populations. These findings provide a comparative framework for discussing the potential relevance of antennal morphology to chemical communication. Conclusion: This study provides information on the structures and dimensions of the antennae and forelegs of the major and minor workers of Solenopsis geminata. Integrating these observations with recent publications on OBPs and chemical ecology provides a basis for future investigations combining antennal ultrastructure (SEM), protein analysis and chemical profiling to examine the relationship between morphology and chemical communication.