AND PROBLEMS OF SOUTHERN NIGERIA. 207 



the species is to be regarded only as a destructive casual remains to be seen. 

 The treatment for these pests should be similar to that recommended for the 

 following insects. 



Leaf-eating Beetles. 



Adoretus hirtettus, Castn., was only noticed in the Western Province, at 

 Lagos, Agege and Ibadan ; but it is known to be generally distributed in West 

 Africa. 



The beetle feeds on the leaves of cocoa and kola, eating only the soft tissue 

 between the very small veins and if left alone will completely skeletonise a leaf. 

 Leaves affected by this beetle can easily be distinguished by this feature 

 (Plate XXVIII, fig. 2). Grasshoppers are not so particular, and make larger 

 holes; while caterpillars usually commence operations at the edge of the leaf and 

 consume the whole leaf substance. To watch the pest at work it is necessary to go 

 with a lantern at night and look on the underside of the leaves. On quite young kola 

 plants, with only half a dozen leaves, as many as four beetles have been observed 

 chewing away steadily. They fly at night and are attracted to light. During the 

 day, they lie hidden in the soil quite near the surface and within 3 inches of the 

 base of the plants. Their greenish-brown colour and inactivity render them un- 

 obtrusive and liable to be overlooked. Though they were only found at first 

 during July, there does not seem to be any off-season with them, as leaves bearing 

 characteristic holes may be found at any time of the year. 



While searching for the adults in the soil many chafer grubs about 1 inch 

 long were found. They were more numerous than the beetles. Once, in July 

 1912, a white pupa and its cast larval skin were dug up. The larval skin was 

 very similar to that of the chafer larvae, while the pupa was similar to the adult 

 Adoretus. Unfortunately the pupa died, and though grubs were kept for a few 

 months none pupated. It is probable that these were the larvae of this beetle, 

 but further investigation is necessary. 



This beetle was certainly one factor in retarding the growth of about 475 

 cocoa and 182 kola plants at the Government Model Farm, Agege. In the 

 nursery at Ibadan any one passing could not but remark the severe damage 

 caused by the pest. 



Treatment of Leaf -eating Pests. 



At Agege the caterpillars of Diacrisia maculosa were frequently observed to 

 pass between the cocoa plot and an adjacent maize plot, feeding well in cither, 

 and their activity was remarkable. The juxtaposition to cocoa of a crop like 

 maize, which provides abundant food and is difficult to work for caterpillars, is 

 clearly a mistake. 



At Calabar the nursery beds were surrounded by short thick grass and weeds 

 and abundance of Plusia acuta caterpillars were found thereon and upon the 

 young cocoa. Whether the grass and weeds provided food for the larvae is 

 doubtful, but they certainly provided plenty of shelter, and the necessity for 

 cleanly farming must again be emphasised. 



