Lipids were extracted from the plasma and gonads of fourth and fifth instars and adults of Dysdercus koenigii (Heteroptera: Pyrrhocoridae). Thin layer chromatography of the extracts revealed fractions of free fatty acids (FFA), monoglycerides (MG), diglycerides (DG), triglycerides (TG), phospholipids (PL), free cholesterol (FC) and esterified cholesterol (EC). There were distinct differences in the lipid profiles within sexes for both tissues during development. Phospholipid from female plasma showed significant fluctuation during development, while that from males remained constant. In female gonads, PL levels increased significantly from the fouth instar to the fifth instar. Monoglycerides were detected only in adult male plasma and adult female gonads, at very low levels. Plasma DG in males was found to increase significantly during development. Maximum gonadal DG was recorded in male fourth instars and female fifth instars. Triglycerides in female plasma declined from the fourth instar to the adult stage. In contrast, TG in gonads increased significantly in the fifth instar of both sexes. Plasma FFA of both sexes fluctuated during development. Free cholesterol was detected only in adult male plasma. Plasma EC increased from the fourth instar to the adult stage in males, and it was highest in gonads of fifth instars of both sexes.

Evaluations of toxicity, antifeedant, growth-regulatory activity of the methanol extract of Gliricidia sepium leaves were carried out against Dysdercus koenigii Fabr. (Heteroptera: Pyrrhocoridae), Achaea Janata Linn, and Spodoptera litura Fab., (both Lepidoptera: Noctuidae). Topical application of 100-300 μg of the extract to different stages of the test insects resulted in dose-dependent effects including larval-pupal intermediates and deformed adults. The highest tested dosage (300 μg/ μl) resulted in reduced survival rate and morphological abnormalities. At certain doses a strong antifeedant activity was evident against the lepidopteran insects.

The occurrence of an orange body coloured mutant, governed by a single somatic recessive gene of the cotton stainer, Dysdercus koenigii is reported. Both the strains did not show any quantitative difference in growth, development and reproductive biology. Males of the orange mutant lacked any special preference for females of orange mutant. Inheritance of the orange mutant in mixed population showed its relative stability at about 21% from F2 to F8 generations. The utility of the orange mutant for studies on population genetics and dynamics of the cotton stainer is discussed.

The phytochemical ptumbagin, isolated from Plumbago zeylanica L., was applied in 2 and 5 μl doses of 0.1% concentration on the surface of Dysdercus koenigii F. adults and its effect on the haemocytes of the bug, studied by transmission electron microscopy. All the five haemocyte types viz. the prohaemocyte, plasmatocyte, granular haemocyte, oenocytoid, and the adipohaemocyte are affected within a period of 24–48 hr. The effect begins with an acute state of vacuolization of the cells and a gradual destruction of the organelles, followed by dissolution of the plasma membrane and passing out of the internal organelles, like the mitochondria and the endoplasmic reticulum. This phenomenon is responsible for a consistent elimination of the haemocytes from the blood, leading to lowering of the resistance and mortality of the insects.

Eucalyptus oil vapour treatment provided to Dysdercus koenigii female individuals as virgin adults or during their fifth instar nymphal life led to a fall in the total protein content accompanied by a rise in the free amino acid titre of haemolymph and fat body. However, the level of total lipids in these two tissues under such condition varied in that a decrease and an increase were recorded in haemolymph and fat body respectively. In the ovary of this adult female, the amounts of total proteins and lipids were low, while the value for total free amino acids was high. The implications of all these findings are discussed chiefly in relation to transport, synthesis and degradation of biochemical constituents in the three tested tissues.