Extract

1. The effects of humidity upon the rate of development of the egg, larva and pupa of Heliothrips haemorrhoidalis, Bché., is quite negligible.

2. The rate of development and reproduction primarily depends upon the temperature.

3. The larva and adult are more resistant to the ill effects of combined temperature and relative humidity than are the egg and pupa.

4. Humidity of above 87 per cent. is the safe zone for the development of the pupa.

5. A temperature-activity scale for Heliothrips is given.

6. The plant tissue wherein the egg is laid may have a detrimental effect upon the egg under certain conditions.

7. The effects of the particular climatic conditions of Palestine on the seasonal abundance of the insect are described.