529 



outside, the house should be closed for four days, then cleared out and the 

 ventilators and doors left open. Houses treated in this way may be 

 replanted after a fortnight. Canes from infested houses should be 

 dipped in bundles for two minutes in lioiling water to kill all mites 

 in them. Out of doors, Convolvulus, which commonly grows amongst 

 staging stacked in the open, is the favourite food-plant of these mites. 

 Tn winter they hide in the crevices of the staging, and are thus taken 

 into the houses the following season. When possible, staging should 

 be washed with the spray fluid and removed to where it is free from 

 weeds. To prevent pots becoming infested in the same way, they may 

 be dipped in boiling water. 



The varieties of tomatos most liable to attack by this pest are 

 recorded. " Comet " and " Blaby " are the most resistant, and the 

 plants should be left imstopped until well on in the summer. 



Departmental Activities : Entomology. — //. Dept. Agric. Union 

 S. Africa, Pretoria, iii, no. 2, August 1921, pp. 108-112. 



An observation is recorded of honey-bees carrying off the wax 

 produced by the wax scale, Ceroplasfes zonatus, on silver wattle. Many 

 species of Coccinellids occur in South Africa, but few are of much 

 economic importance. Cliilocoriis distigma is a conspicuous one, but 

 it has so many enemies that it only occasionally increases to any 

 extent. The fruit moth, Achaea lienanli, was recorded in large numbers 

 on a fig tree (Ficiis natalcnsis), but disappeared in a few days, and no 

 larvae were found. 



It is suggested that the old remedy of drawing a chalk line around 

 furniture, etc., to keep off ants deserves to be better known. Its 

 limitations are obvious, but its application is very simple. The ants 

 cannot cross a chalk line on an inverted, vertical or very sloping 

 surface, as the loose particles give way and they drop to the ground. 

 This applies to the house ant, Pheidole pimctulata, and to the larger 

 ants, such as Plagiolepis cnstodiens, thrips, Coccinellids, small spiders, 

 etc. On trees with smooth bark a band either of soft chalk or charcoal 

 is efficacious, if the ant trail is not too strong. 



Cotton suffered considerably from bollworms, the most important 

 species being Heliothis {Chloridea) obsoleta, particularly in cotton 

 fields near old maize lands, and the Sudan bollworm [Diparopsis 

 castanea] in other localities. For both moths, thorough preparation 

 of land and frequent shallow cultivations have proved the miost 

 practical remedy, the bollworms being destroyed in the soil before 

 reaching the adult stage. The Jassid, Chlorita facialis, breeds in 

 the veld and migrates to the cotton fields, where it seems to increase 

 more rapidly ; in cases of severe infestation the leaves wither and drop, 

 the formation of bolls ceases, and the plants sometimes die, though 

 plants that have been manured maintain their vigour and are able 

 to resist attack. The cotton-stainers, Dysderciis and Oxycarenus spp., 

 are minor pests ; much can be done to eliminate damage from staining 

 by careful picking and the sunning of seed-cotton before packing. 

 The best results are obtained by exposing the cotton in thin layers 

 on sheets of iron laid upon the bare ground. 



Citrus trees were badly injured in one locality by termites, perfectly 

 healthy trees being sometimes complete^ ring-barked in 24 hours. 

 Individuals of the fungus-growing species of Macrotermes were taken 

 at work on a j^oung orange tree. Purchasers of sodium fluoride for 

 use against cockroaches are cautioned against an adulterated form that 



