85 



east monsoon is not too dry, this insect occurs more or less sporadically, 

 though it is to be found the whole year through in all stages of develop- 

 ment. 



The bionomics of this locust are not thoroughly known, and many 

 important points still require investigation. The eggs are laid in any 

 kind of soil about 3 inches below the surface. Three months are 

 required from the egg for the insect to become winged, and the adults 

 live about two months, pairing taking place in the last month of life. 

 In years Avhich are not very dry, the eggs hatch out in a few weeks ; 

 drought delays the hatching, which does not take place until a consider- 

 able amount of rain has fallen in November or December ; in this case 

 there will be a more or less sudden appearance of the insects in large 

 numbers. About the end of the west monsoon, these will be full 

 grown and the eggs will be laid more or less at the same time. If the 

 new east monsoon is then very dry, at the end of it there wall be a still 

 greater accumulation of locusts, and if these conditions be repeated a 

 third time, the number of locusts in the next west monsoon may reach 

 disquieting proportions. This is the explanation suggested for the 

 connection between dry years and the locust plague in Java. The 

 view that the eggs may lie unhatched in the ground for several years is 

 regarded as untenable, although eggs that have been kept dry in the 

 laboratory for over a year have been found to be still living. The local 

 outbreaks of 1914, followed by a general and serious infestation of all 

 wooded areas in 1915, are considered to bear out the theory of delayed 

 hatching between the monsoons. In the latter year, the damage done 

 in some places is said to have been indescribable. 



The desire of the locusts for sunlight and warmth causes them to 

 attack the tops of the trees first. The damage to old trees is not very 

 serious ; the younger the tree, whatever the species, the greater the 

 damage. When the winged stage is reached, the insects exhibit a 

 marked tendency to change their locality, but this movement, though 

 more or less general, is not comparable with that of other well known 

 species which migrate in vast swarms. The Java locust spreads 

 steadily from the teak forests and gradually invades the surrounding 

 cultivated land and this process may go on for several weeks. At a 

 distance of a little over three miles the danger to crops is usually 

 small. 



The food-plants of this locust are discussed at length. The plants 

 that are regarded as safe from attack, include : — Mahogany, rice, 

 lalang grass [Invperata cylindrica], Sacckarum sjjontaneum, and Coleus 

 (uberosus (black potato). Castilloa, bread-fruit, Ficus and Hevea are 

 favourite food-plants, and are all eaten in the same manner, the young 

 leaves at the tips of the branches being generallv spared. The green 

 shell of Java coffee is eaten, but not that of Coffea robusta. Coconut 

 palms almost beyond the danger zone are often seriously attacked, 

 while other crops near by are left. Sorghum is but slightly attacked, 

 though maize suffers seriously. 



The secondary foci outside the teak forests are productive of much 

 greater damage to crops, as in these the insects are not immigrants, 

 but -residents. 



In dealing with the c[uestion of control, all the well-known methods 

 are reviewed in relation to the habits of the Java locust. A fungus, at 

 present indistinguishable from Metarrhiziion anisopliae, plays a very 



