INJURIOUS TO THE LEBBEK TREES OF CAIRO. 123 



Spread of the pest to other trees ; but an examination made at the time by 

 the author of this paper showed that the mealy bug was present, not only on 

 other trees in the same street, but also in many other parts of the town. 



The pest did not again become conspicuous until the summer of 1909, 

 when in certain streets of the city it increased at an alarming rate and gave 

 rise to the death of a large number of trees, and, in addition, caused loss 

 and inconvenience in other directions. Its depredations during the past 

 summer now entitle it to rank as a lebbek pest of the first importance ; but 

 it is fortunate that this scale-insect only becomes at intervals sufhciently 

 numerous to be injurious, and it is believed that one reason, if not the chief 

 one, for its unusual increase is an unhealthy condition of its host-plant. 



Food Plants, 



In addition to the lebbek {Alhizz'ia lehbek) and cotton (Gossypiam spp.), 

 D. perniciosus has been found on Christ's Thorn (Zizj/phus spina- christi) and 

 on the Sunt Tree {Acacia arahica). 



The lebbek is an introduced species, but the date of its introduction into 

 Egypt is not known. Sunt (Acacia arahica) is indigenous in many parts of 

 Africa, including Egypt, and it may be the original host-plant of the mealy 

 bug, from which it has spread to the lebbek. The Sunt is a very common 

 tree in this country. 



Distribution of the Lebbek Mealy Bug. 



At present we possess a very scanty knowledge of the distribution of this 

 pest. In Cairo it has appeared up to the present in most, if not all, of the 

 streets in which lebbeks are grown. It occurs also on Ghezireh Island and 

 the Gizeh side of the river Nile. The only other locality from which the 

 species has been recorded is Marg, a village some ten miles from Cairo. 

 No doubt further search will show it to be present in many other parts of 

 Egypt. 



There are no records to show for how long this species has been present 

 in Cairo; probably it has been therefor many years, although only discovered 

 for the first time so recently as 1907. 



Life-History and Habits, 



The life-history of this insect has not been worked out in detail. From 

 general observations made up to the time of writing, it appears to breed 

 continuously throughout the year. Eecently (January, 1910), after a spell 

 of unusually cold weather, during which the thermometer in the screen 

 on two nights registered several degrees of frost, colonies of females were 

 found on lebbek trees in Cairo with well-developed ovisacs, containing 



m2 



