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holes in it, but in these cases, the larva generally quits the leaf-tissue 

 and begins a fresh burrow in a vein. From the midrib, after boring 

 out the pith, the larva reaches the main stem through the petiole and 

 makes its way to the growing point. If the egg has been laid on an 

 old, fully developed leaf, the larva rarely reaches the main stem, but 

 ' completes the stage in the petiole. The larval stage lasts from 21 to 24 

 days, and as soon as the time for pupation arrives, the larva bores an 

 outlet to the exterior, leaving the epidermis over the hole, the trans- 

 parent spots thus produced being readily visible on attacked plants. 

 The larva then retreats somewhat and spins a small but very thick 

 cocoon. The pupal stage lasts 6-8 days and the whole life-cycle 34-37 

 days. 



With regard to the question as to what becomes of this insect during 

 the time that there is no tobacco on the fields, the author's experi- 

 ments showed that both sexes only live a couple of weeks after pairing. 

 Observations are in progress on a large number of autumn tobacco 

 plants with the object of determining whether the pest survives as a 

 dormant larva, a pupa or as an imago, and also whether there is some 

 other food-plant which enables the insect to tide over the intervals 

 between the tobacco crops. De Bussy has sought for such an alter- 

 native food-plant near Deli for seven years without avail, and the author 

 has examined all possible plants wild and cultivated also without result. 

 As P. heliopa is indigenous to Java and has spread from the East 

 Indian archipelago to Australia on tobacco, while tobacco is not 

 indigenous, it follows that there must be an alternative food-plant, 

 though wild tobacco to a large extent serves this purpose at present. 

 The author has not been able to discover in Besoeki the parasite found 

 by de Bussy in Deli, and up to the present no insecticides have given a 

 useful result. As the infestation was thought to take place on the very 

 young plants in the nurseries, covering with mosquito- netting as soon 

 as night fell was tried, but this method is considered useless because 

 the real infestation takes place after planting out, while, in the nurseries, 

 tlie fact that the plants are close together prevents oviposition and 

 only those on the borders of the beds are attacked. On the other hand, 

 freshly planted tobacco is attacked before the young plants have had 

 time to recover from the effect of removal and therefore resist so badly 

 that large numbers of them die. As the larvae can apparently feed 

 on and develop in withered plants, all these should be burned and all 

 seedlings in the nurseries, not planted out, should be similarly 

 destroyed. 



The third article of this series deals with a new and serious pest of 

 fermented tobacco. The head of a large tobacco factory at Besoeki 

 complained that the fermented and baled leaves were seriously attacked 

 by an insect which was apparently not the well known pest, Lasioderma 

 serricome, F. This proved to be a Tineid moth, the stages of which 

 are described and figured. The egg-stage lasts seven or eight days ; 

 attempts to determine the length of the larval stage failed. The 

 larvae make galleries between the bundles in the bale which are lined 

 with excrement and loose web ; they move rapidly when disturbed 

 and are very sensitive to light ; the cocoons are enveloped in excre- 

 ment. The pupal stage lasts 15 days. On opening a bale, quantities 

 of the larvae are to be found and the upper layers of leaf bundles are 

 seen to be eaten and bored to a depth of about 2 inches so that all bales 



