80 



instead and the larvae speedily buried themselves in these. The 

 length of the larval stage was difficult to determine, but probably, on 

 an average, lasts about four months. Pupation takes place about 

 4 inches below the surface ; the pupal stage is very short, being barely 

 a week. During the West Monsoon, the beetles are very sluggish but 

 they are active in August and December and fly in swarms to lamp 

 light. Microscopical observations of the ovaries from January to 

 May showed that the eggs are not ripe until May and it would thus 

 appear that the beetles are not sexually mature till six or seven months 

 after emergence, viz., in the months of June, July and August, and 

 thus the whole life-cycle of the insect embraces nearly a year. Both 

 adult and larva damage tobacco, the former gnawing the root-collar 

 and the latter the tap-root. The damage done by 0. depressimi in some 

 places is very marked, and frequently the whole of a plot of planted 

 out tobacco is destroyed by the beetles or the larvae. This occurs 

 chiefly with autumn tobacco ; spring tobacco, which is generally 

 planted out in February and March, is but little attacked because at 

 this season no larvae are present and the beetles are not feeding freely. 

 The destruction of spring tobacco is generally due to Melolonthid 

 larvae and very often to the operations of large earthworms. 0. de- 

 'pressmn frequently does much damage also in coffee plantations. The 

 attacks of this pest are often very local, and in an experimental field 

 planted with spring tobacco, which had carried various kinds of 

 leguminous plants in the previous year, only those sections of the field 

 were attacked by the beetles which had been previously planted with 

 Phaseolus lunatus. Though the beetles come in swarms to light, poor 

 results were obtained in trials of this method of capture. Flooding 

 the soil or setting traps of banana leaves, on the upper side of which 

 the larvae collect, is more effective, and spraying with a solution of 

 soap and tobacco extract is also suggested. Earth containing 5 per 

 cent, of naphthaline placed at intervals between the rows of plants, 

 as advised by the Deli station, did not prove successful, as the naph- 

 thaline soon evaporated. Spraying the soil with a 1 per cent, solution 

 of potassium sulphocarbonate is suggested as probably effective and 

 experiments with this are in progress at Deli. 



The identity of the moth, known in Deli as " toa-toh " and by other 

 names in other parts of Java, is discussed at some length. It has been 

 generally known as Lita solanella, Boisd, which is a synonym of 

 Phthorimaea operculella, ZelL, the world-wide potato pest. Although 

 attacking the potato tuber, the latter moth is as a matter of fact more 

 especially a miner of the upper surface of the leaves and stems of the 

 potato, tomato, aubergine and other Solanaceous plants, and also of 

 tobacco. P. operculella is thus in no sense a definite stem-borer, as is 

 the moth under consideration, and the author is convinced that the 

 East Indian toa-toh is Phthorimaea (Gnorimoschema) heliojM, Low., 

 recorded by Lefroy as the " tobacco stem-borer " and known as such 

 only in British India, Ceylon, Sumatra, Java and Australia.* The 

 eggs are generally laid on the leaves and the egg-stage lasts about five 

 days, the newly-hatched larvae being so small as to be almost invisible 

 to the naked eye. The larvae bore into a vein of the leaf and quickly 

 reach the midrib ; occasionally they bore into the leaf-tissue and make 



*|Tliis moth is well known as a tobacco pest also in East and South 

 Alrica. — Ep.] 



