Differential haemocyte counts of 5th instar nymphs and adults of Dysdercus cingulatus Fabr (Hemiptera: Pyrrhocoridae) treated with acephate, an organophosphorus insecticide

Five types of haemocytes have been identified in the haemolymph of 5th instar nymphs and adults of the redcotton bug, Dysdercus cingulatus. Changes in the Differential Haemocyte Counts (DHCs) have been assessed inrelation to application of graded concentrations of Acephate. The haemogram profile was determined 6 hr, 1 day,3 days, 5 days post-treatment as well as post-moulting i.e. in the adult males and females. Different types ofhaemocytes registered a dose-dependent response by either exhibiting increase or decrease in their relativeproportions. The adipohaemocytes were the most sensitive cells to the insecticidal stress whereas theoenocytoids showed least damage to their cellular integrity. However, there was a consistent increase in theproportion of damage/unidentifiable blood cells in accordance with increase in concentration of acephate applied.Furthermore, the treated insects apparently responded by releasing more prohaemocytes, the so called “stemcells”, into the circulation as evident by increase in the percentage of these cells in treated blood smearscompared to the parallel control.