The reactions of the soft scale insect Kilifia acuminata (Signoret) towards some environmental factors namely light, temperature and air humidity have been studied experimentally in the laboratory, to detect their effectiveness on the insect's orientation towards its habitat. The mechanisms of the insect's orientation towards these factors have been also discussed. Light seems to be the most important factor regulating the insects distribution on different zones of the mango trees in natural conditions in all seasons and this is followed by temperature.


The soft scale insect, Kilifia acuminata (Signoret) reacts positively to light. The simple eyes are the photoreceptors by means of which the insect can sum up the light from various directions and steers in a path towards the high intensity beam. The insect reacts skototactically towards dark objects.

The linear velocity of the insect significantly increases with the increase of temperature. It has a zone of thermopreferendum extending between 22° and 32°C. Above 37°C, the insect is sensitive to small temperature differences of 2°C.

At different humidity combinations below 75% R.H., the insect prefers the moist side, while in the upper range above 83% R.H., it usually prefers the dry side. The preferred zone of humidity extends between 75 and 83%.

Orthokinesis, klinokinesis and klinotaxis are the main mechanisms regulating the insect reaction towards different physical factors.

The insect behaviour and its correlation to the normal environment is also discussed.