1 68 First Report on Economic Zoology. 



The most favourable time to treat them is in the evening — damp 

 weather if possible being chosen — as the increase of the fungus is doubtfid 

 unless the air is moist. 



Further experiments should be conducted, however, before this is 

 definitely considered satisfactory. 



B. 5. Plants Poisonous to Locusts. 



1. Common Garden Larkspur {Delpliinium). 



2. Castor Oil Plant {Ricinus communis). 



These might be employed around gardens, orchards, etc., as a barrier 

 to the advance of locust armies. 



It should be pointed out, however, that stock will eat Larkspur and are 

 thereby poisoned {vide Dr. E. V. Wilcox's Rept., Bull. 15, Montana Exper. 

 Station, 1897, on " Larkspur Poisoning of Sheep "). 



B. G. Natukal Enemies. 



Locusts suffer from many natural enemies, both vertebrate and inver- 

 tebrate. Amongst the former may be mentioned fowls and turkeys. 

 Droves of the latter clear off locusts very rapidly, as many as fifty being 

 found at once in a turkey's crop. Encouragement of these birds should 

 be given in all districts where locusts abound. Numerous ^vild birds also 

 feed off locusts. 



Amongst insect enemies are numerous diptera or flies, especially 

 Tachina Flies {Tac/iinidce), and Flesh Flies (Sarcophagid(B), Avhose larvae 

 or maggots live inside and destroy the young locusts. 



Many carnivorous flies, such as the Asilidte, or " Wolf Flies," feed off 

 the young " hoppers." 



Predacious beetles and their larvae devour locusts in different parts of 

 the world, especially the locusts' eggs. 



In North America a species of mite, /. locvstarnm, Riley, is the most 

 effective enemy of the various locusts. These mites feed oft" the eggs and 

 also the winged adults. 



No natural enemies are able to cope with locusts, however, unless it be 

 the Locust FungU!^ {Eminisa gnjllii) (vide B. 4), 



(Signed) Feed. Y. Theobald. 



Sudan Government, 



Civil Secretary's OflBce, Cairo, 



Zrd November, 1901. 

 To C. E. Fagan, Esq., Assistant Secretary, 



Natural History Department, British Museum. 



Dear Sir, — I beg to thank you for your letter of the 17th October 

 enclosing some very valuable suggestions for the destruction of locusts. 

 They should eventually prove of the greatest use, though as yet the Sudan 

 is too new and too thinly populated to permit of operations being carried 

 out very effectively. 



