May, 1909.] 



115 



Plant Scmitation, 



140) :— "Throughout Virginia and 

 est Virginia, where the spruce pines 

 have for some years suffered so severely 

 from the destructive work of Dendroc- 

 tonus frontalis, not a single living 

 specimen of the beetle has been found 

 during the present year. The clearest 

 explanation of this sudden change is 

 that the species was practically killed 

 out by the exceptionally severe cold of 

 last winter, since such was the case 

 with several other insects. Now, follow- 

 ing so closely on the introduction by 

 Mr. Hopkins of Clerus formicarius, how 

 easy it would have been to attribute 

 the sudden decrease to the work of the 

 introduced Clerus had not the decrease 

 been so general and extensive as abso- 

 lutely to preclude any such possibility." 



Such coincidences emphasise the care 

 that is necessary in the scrutiny of 

 apparently successful results. 



I have been unable to find any later 

 references to this experiment. Nor do 

 I know whether it was finally crowned 

 with success or not. 



Clerus formicarius is itself a beetle 

 of predatory habits. In its adult stage 

 it preys upon other beetles smaller and 

 weaker than itself. It should be noted 

 that it is (compared with the minute 

 size of the ' shot-hole borer') a compara- 

 tively large insect, and is consequently 

 unable to penetrate the galleries of the 

 borer. It lays its eggs in the entrance 

 of the tunnels and its larvae follow up 

 and devour those of the borers. 



The family Clerxdce is already re- 

 presented in Ceylon, but none of our 

 local species appear to have concerned 

 themselves with the destruction of 

 Xyleborus fornicatus. It is probable 

 that, being themselves indigenous to 

 the country, they have accustomed 

 themselves to prey upon other indi- 

 genous insects. It is most probable that 

 the 'shot-hole borer' of our tea is an 

 accidental introduction of compara- 

 tively recent date. 



MISCELLANEA: CHIEFLY 

 PATHOLOGICAL, 



In view of the statement that Loran- 

 thus is attacking acacia trees in up- 

 country districts, it is of interest to note 

 that, in a study of the life-history of an 

 Australian species, Loranthus exocarpi, 

 the host plants in the neighbourhood of 

 Myrniong, Victoria, comprised Acacia 

 decurrens, Acacia dealbata, Acacia mela- 

 noxylon, three other acacias, Cherry, 

 Plum, two species of Casuarina, and 



five other plants. Evidently Acacia is 

 particularly liable to be attacked by 

 this parasite, though the relative 

 frequency of the trees named in the 

 district is not stated. Th^re are 

 twenty-five species of Loranthacea? in 

 Ceylon, six of which are restricted to 

 the moist low-country, three to the dry 

 region, and seven to the montane zone ; 

 the remainder are more generally, but 

 capriciously, distributed. Six are said 

 to be very rare, three rare, and four 

 rather rare. A list of the host plants 

 of the Loranthacem of Ceylon has 

 never been compiled ; Trimen mentions 

 Rhododendron, coffee, SaLvadora, Sym- 

 plocos, Eurya as hosts of various 

 species. The compilation of such a list 

 would provide interesting work for a 

 local botauist, and might subsequently 

 lead to valuable information with regard 

 to the conditions which render some 

 trees particularly liable to be attacked 

 by these parasites, while others in the 

 same neighbourhood are immune Cacao 

 is attacked at Peradeniya, and a good 

 example may be seen near the well out- 

 side the station ; mango trees especially 

 suffer ; and the branches of the clove 

 are killed back by it. Camphor is 

 attacked at Hakgala. It may be noted 

 that specimens should be collected in 

 flower and fruit, with examples of the 

 host plant in the same state, if possible, 

 in order to ensure accurate determina- 

 tions. 



In a recent case of tea root disease, 

 Rosellinia spread from the tea to the 

 dadaps and killed them out. This need 

 not be taken as a sign that dadaps 

 should not be planted, for Rosellinia 

 does not originate either on tea or 

 dadaps, according to our present in- 

 formation. Indeed, it is only what 

 might be expected, since the true 

 Rosellinia radiciperda, Mass., which was 

 discovered in New Zealand on fruit trees, 

 killed out grass and any other plants 

 which happened to come in its way. 

 In the same way, the chief Ceylon 

 Rosellinia — which is Rosellinia bothrina, 

 Berk., and Broome, not Rosellinia radici- 

 perda, which has not been found in 

 Ceylon— spreads from tea to Panax, 

 and kills the latter with astonishing 

 rapidity ; but it leaves untouched any 

 cacao or Hevea which happen to stand 

 in its path. Such selective parasitism 

 is not uncommon, though it is not such 

 a universal rule as a study of the 

 Uredineai (i.e., Hemileia) would lead us 

 to expect. Fomes semitostus attacks 

 Jak and Hevea— both, it may be noted, 

 laticiferous trees, though it is improbable 

 that that is the controlling factor — but 

 it does not spread to tea or cacao even 



