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 doubtful 
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 ( 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. V. Wilcox’s Rept., Bull. 15, Montana Exper. 
Station, 1897, on “ Larkspur Poisoning of Sheep ”). 
B. G. Natural 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 wild birds also 
feed off locusts. 
Amongst insect enemies are numerous diptera or flies, especially 
Tachina Flies ( Tachinidce ), and Flesh Flies (Sarcophayidce), whose larvae 
or maggots live inside and destroy the young locusts. 
Many carnivorous flies, such as the Asilidae, 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, /. locustarum , Riley, is the most 
effective enemy of the various locusts. These mites feed off the eggs and 
also the winged adults. 
No natural enemies are able to cope with locusts, however, unless it be 
the Locust Fungus ( Empusa gryllii) ( vide B. 4). 
(Signed) Fred. Y. Theobald. 
Sudan Government, 
Civil Secretary’s Office, Cairo, 
3rd November, 1901. 
To C. E. Fagan, Esq., Assisi ant 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. 
