396 



GuNN (D.). The Cucumber and Vegetable Marrow Fly, Bacus verte- 

 bratus. — Union of S. Africa. Dejit. Agric. Pretoria, Div. Entom, 

 Bull. no. 9, 1916, 6 pp. [Received 19Dh July 1916.] 



The Trypetid fly, Dacus vertebratus, has been an important pest for 

 many years in most parts of the Union of South Africa where cucumbers, 

 vegetable marrows, pumpkins or water-melons are grown, and in many 

 gardens the cultivation of these plants has had to be abandoned owing 

 to its presence. The eggs are deposited in the rind of Cucurbitaceous 

 fruits at a depth of about 2 mm., chiefly on the lower side of the fruit. 

 The number of generations was not ascertained, but egg-laying was 

 found to be continuous throughout the summer. The period of 

 incubation varies, occupying from 2 to 4 days in the insectary. The 

 larva possesses two large and conspicuous chitinous hooks, by means 

 of which it burrows in the fruit. The larval period varies from 15 to 18 

 days ; pupation takes place in the soil at a depth of from a quarter 

 of an inch to two inches. The chief injury appears to be done early 

 in November before the heavy rains begin, as the flies are extremely 

 active during dry, sunny weather. Cold, wet weather has a detrimental 

 effect upon them and retards oviposition. The adult stage lasts from 

 1 to 9 months, according to experiments made in the insectary. No 

 parasites emerged from puparia in the insectary. Remedial measures 

 must be applied before melons, cucumbers, etc., are attacked. 

 Oviposition usually begins when the fruit is about a quarter grown, 

 but in order to ensure success, baiting should be undertaken imme- 

 diately after its formation. In the experiments, fully 95 per cent, of 

 the crop was saved from destruction on rows treated before the 

 deposition of eggs, whereas all the fruit on the untreated rows was 

 destroyed. D. vertebratus is extremely fond of sweet material and a 

 sweetened poison-bait was placed upon the foKage and fruit of cucur- 

 bits. The following formulae were used : — (1) Arsenate of lead paste, 

 3 oz. ; unrefined treacle or molasses, 2 lb. ; water, 4 gals. ; (2) 

 Arsenate of lead paste, 3 oz. ; unrefined treacle or molasses, 2 lb. ; 

 glycerine, 3 oz. ; water, 4 gals. ; (3) Arsenate of lead paste, 3 oz. ; 

 coarse sugar, 2\ lb. ; water, 4 gals. The rainfall during November, 

 December and January being exceptionally heavy, a great deal of 

 inconvenience was caused by the necessity for frequent renewal of the 

 bait. Experiments repeatedly demonstrated the fact that a shght 

 shower of rain (from 0'06 to 0*13 inch) completely washed away no. 3 

 mixture, whereas nos. 1 and 2 proved more adhesive. If nos. 1 and 2 

 mixtures are used during dry weather, they would have to be renewed 

 every twelve or fourteen days, and during wet weather, after about a 

 fifth of an inch of rain has fallen. An ordinary garden syringe may be 

 used for applying the bait. When fruits become infested, they should 

 be removed and buried in the soil at least two feet deep. 



Theobald (F. V.). Aphididae found on the Apple in Britain and the 

 Description of a New Species from Africa. — Canadian Entomologist, 

 Londo7i, Ont., xlviii, nos. 5-8. May-June-July-August 1916, 

 pp. 169-177, 202-214, 233-242, 261-263, 6 figs. 



This paper gives a detailed account of eight species of Aphids 

 infesting the apple in Britain with a key to them. The food-plants. 



