UPON SCALE-INSECTS. 61 



produces both kinds of fructifications. Hence the ascus 

 stage is only to be expected in old material. In fact some- 

 times they may not be formed till the leaf has fallen. 



Economic Value. 



As regards the economic importance of these fungi, they 

 have only as yet been used with success in the United 

 States. Webber considers Aschersonia and its associate the 

 sterile brown fungus as most useful in checking and even 

 eradicating the mealy-wing (Aleurodes citri), and so in- 

 directly the sooty mould of the orange. Rolfs, Forbes, and 

 Gossard have shown that Microcera coccophila can be em- 

 ployed as a permanent check to the harmful San Jose Scale. 

 In fact under certain circumstances the fungus is considered 

 to be quite capable of controlling this pest without the 

 aid of artificial insecticides. The conditions favourable for 

 its growth are, as one might expect, moisture and warmth. 

 For these reasons Ceylon should be especially suitable for 

 experimental work with these natural enemies of scale- 

 insects. 



Perhaps a little caution should be exercised before making 

 use too freely of these fungi, till their peculiarities are 

 thoroughly known. Some species of Nectria are noted 

 "wound" parasites on trees. The cacao-canker of Ceylon, 

 recently studied by Carruthers, is due to a Nectria. It would 

 be interesting to experiment and see if the scale Nectria 

 of Ceylon could act as a " wound " parasite. Will its eonidia 

 germinate and cause disease when placed in a wounded 

 region of a plant, especially such a one as is frequented 

 by the particular coccid ? It is hardly likely, but perhaps 

 advisable to try, before recommending such a fungus as 

 a remedy for certain scale pests. 



Considering the importance "biological" species have 

 assumed in the case of Rusts (Uredineae) and Mildews (Ery- 

 sipheas), it would be instructive to see if anything of the 

 kind exists amongst these scale-fungi. For example, will 



