1 68 First Report on Economic Zoology. 



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

 weather if possible l)eing chosen — as the increase of the fungus is doubtful 

 unless the air is moist. 



Further experiments should l^e conducted, however, before this is 

 definitely considered satisfactoiy. 



B. 5. Plants Poisonous to Locusts. 



1. Common Garden Ijarkspur {Delphinium). 



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. Y.Wilcox's Kept., Bull. 1.5, Montana Exper. 

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



B. 6. Natural Exe^iies. 



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

 tebrate. Amf)ngst 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. Xumerous wild birds also 

 feed off locusts. 



Amongst insect enemies are numerous diptera or flies, especially 

 Tachina Flies {TachinidcB), and Fle.-h Flies {Sarcoiihagidce), whose larvae 

 or maggots live inside and destroy the young locusts. 



Many carnivorous flies, such as the Asilida, 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, /. locvstarvm, Piley, is the most 

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

 also the winged adults. 



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

 the Locust Fungus {Empusa grylUi) {vide B, 4). 



(Signed) Fred. Y. Theobald. 



SUEAN GOVERXMEKT, 



Civil Secretary's Office, Cairo, 



Srd November, 1901. 

 To C. E. Faoan, 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 l)eing carried 

 out very effectively. 



