53Importance of Formic Acid
in Various Ethological States of
Oecophylla smaragdina (Fabricius)
VV Vidhu and DA Evans
A. K. Chakravarthy (ed.), New Horizons in Insect Science: Towards Sustainable Pest Management,
DOI 10.1007/978-81-322-2089-3_6, © Springer India 2015
VV. Vidhu () · DA. Evans
Department of Zoology, University College, University
of Kerala, 34, Thiruvananthapuram, Kerala, India
e-mail: [email protected]
DA. Evans
e-mail: [email protected]
Abstract
In polymorphic colony of Oecophylla smaragdina Fabricus, the content
of formic acid (FA) in major workers was 9.7 ± 0.7 mg/gm tissue which
was one forth of the content of minor workers, one third of the content of
intermediate workers and 10 times higher than non-biting reproductive
forms. Larvae and pupae had no traces of FA in their body. During the 24 h
cycle, the major workers showed a chemical rhythm in content of FA with
a peak at noon and low amounts in morning, evening and night. The work-
ers aggressively defend enemies by painful bite with sharp mandibles and
simultaneous spray of FA and some of them continued biting until they
died, at which time the FA content decreased to non-detectable amounts
and the body weight was reduced to 60 % of the original weight. Continu-
ous disturbance caused an increase in the content of FA in workers. Con-
tinuous bite for 30 min resulted in a significant increase in the content of
protein together with a decrease in the content of free amino acids (FAA)
and complete stoppage of activity of transaminase enzymes together with
a sharp decline in uric acid and urea in both head and thorax. Slight but
significant decrease in glucose together with no significant change in the
contents of glycogen and lactic acid after 30 min of biting highlights the
efficiency of insect tracheal system in supplying O 2. A sharp increase in
acetylcholine (Ach) in head and thorax may be the reason for the observed