LOCUSTS IN AFRICA. 
51 
he does not believe the swarms arise at once en masse (as though by a 
preconcerted signal), but, inhabiting this whole country, the isolated 
individuals join the group as it passes, thus augmenting it as it pro- 
ceeds ; hence, the longer the distances and the more the wind favors, 
the larger will be the swarm. He says they generally come into the 
French possessions of North Africa under the influence of a hot wind 
from the south, known in Algiers as the sirocco. This wind attains in 
Algiers a temperature of 51° (cent.), as he has ascertained by observa- 
tion of many days in succession. 
The three chief invasions of this section were in 1845, 1864, and 1866. 
Bolivar's statements in reference to this species will be introduced 
hereafter, when we come to consider the question of passage across the 
Mediterranean Sea from Africa to Europe. 
Eev. Samuel Gobat 122 makes the following statement in reference to 
an invasion he witnessed near Axum, in Abyssinia, in June, 1831 : 
The air was teeming with locusts, by which the light of the sun was already greatly 
obscured. But this was only the advanced guard. On looking toward the north I 
perceived, about a league distant, several faint clouds, as it were, rising from the 
earth, which I at once took for locusts, having before seen this appearance of them 
near Cana of Galilee. Afterward this mist became so thick that it entirely hid the sky 
and neighboring mountains from our view, and the people of the country, though ac- 
customed to seeing locusts, no longer believed these wonders to be occasioned by them; 
but the locusts soon arrived tTo convince us of the fact. The air was so darkened that 
we could scarcely discern the place of the sun ; and the earth was so completely cov- 
ered with these insects that we could see nothing else. Children running about the 
fields, at only a stone's throw, could scarcely be seen through the multitudes of locusts 
surrounding them. Every year there is a greater or less descent of locusts in Tigre, 
but they are much more numerous this year than usual. 
He states that they are rarely found "beyond" (southwest of) theTa- 
cazza Eiver. 
Henry Salt 123 says that during his stay in the bay of Amphila a large 
flight of these insects came over to one of the islands and in a few days 
destroyed nearly half of the vegetation. He describes, as before stated, 
a species seen at Bombay, which he asserts was the same as seen here. 
James Hamilton 124 mentions passing through a swarm in the latter part 
of April, 1854, on the Eahat, a branch of the Blue Nile, about N. lat. 14° 
10', E. long. 34o 10'. 
Barth, in his Central Africa 125 , remarks as follows : "I was here not 
a little surprised at the swarms of locusts which the wind drove into our 
faces and which certainly indicated our approach to more fertile re- 
gions." it was July, 1854, and he was then on the Niger about Gaben, 
N. lat, 16° 30', E. long. 0° 20', going south a little east. The southern 
limit of the desert he places at the latitude of Gao (or Gogo), N. lat. 17°. 
The oft-quoted description of locust flights by Adanson 126 relates to 
m " Journals of a Residence in Abyssinia," p. 392. 
m "Voyage to Abyssinia in 1800 and 1810," p. 172. 
m " Sinai, the Hadjaz, and Soudan," p. 297. 
m London Edition, V, p. 242. 
"•"A Voyage to Senegal." The isle of Goree, and the river Gambia. Engl, transl., p. 159. 
