319 



the whole plant rarely reaching a height of more than two 

 and a half or three feet. 



This plant, like others in the locality, has considerable 

 powers for resistance to drought, for here many months may 

 ])ass l)etween rains. Under such circumstances, the Euphorhia 

 may lose its leaves and remain leafless. Branches broken 

 down but not entirely separated from the parent plant may 

 have their wonnds closed with the copious milky juice and 

 callous over without dying. 



Xeoclijtarhis apparently does not attack the living plant but 

 only the freshly dead stems before they are too much weathered. 

 It is probable that the conditions prevailing in this region 

 furnish this insect more material to breed in than ever was 

 availal)le before the natural conditions were changed. The 

 season of 1919, having been abnormally dry led to the death 

 of an unusually large number of the plants. Three things 

 were observed killing the plants or putting their branches in 

 condition for N eoclytarlus to breed in. 



An armoured scale, as yet undetermined, occasionally be- 

 comes numerous enough at the base of the plant to kill it. 

 Even if it does not kill the plant it may so weaken it that 

 the immigrant Cerambycid, Lagochcirus ohsoletus Thomson, may 

 attack the weakened stems. This species frequently attacks 

 the ])lant and completes its transformations after destroying the 

 main stem and branches while the plant is living, the finer 

 twigs being still green and flowing with the milky juice. The 

 attack, however, ultimately results in the death of the plant 

 and its utilization by the NeoclytarJuft. Many plants unfavor- 

 ably situated may be so weakened by drought as to fall victim 

 to these beetles without previous injury by the scale insect. 

 The presence of cattle on this area results in a great deal of 

 mechanical injury through their trampling, many branches 

 being broken off and the whole plant often broken down, yet 

 putting many branches in condition for the N eoclytarlus to 

 l)rced in. Whatever the cause of dying may be, the Neocly- 

 hnhis utilizes a plant quite thoroughly before it has time to 



