224 Miss A. L. Embleton on the 



creature passes unobserved as the scales continue to adhere 

 to the plant, and show to the uuaided eye nothing to 

 indicate that they aie really exterminated. The question 

 as to the distinguishing marks by wliich one may recognize 

 scales that are parasitized is one of great interest, bearing 

 as it does on the practical operations for controlling tlie 

 diffusion of Coccid/v. 



Returning to Comys infelix, the parasite of Lecanium 

 licmis'ph.Trienm. During the latter stages of the develop- 

 ment of the fly within the scale, it becomes evident from 

 the outside which scales are parasitized and which have 

 escaped attack. At first there is little or no difference in 

 the scales ; then it is noticed that those containing the 

 larval fly look rather whitish and swollen. Later on as 

 the pupa inside develops and becomes black, the scale can 

 be seen to be swollen and black. In the fully-grown con- 

 dition it is very evident when the fly is present, for the 

 scale looks black itistead of brown, due doubtless to the 

 black pupa inside. The scale is more narrow and 

 arched than in the normal condition. In the earlier stages 

 it needs more experience before deciding which scales con- 

 tain the parasites ; those sheltering the large white larva 

 \ook rather more pale and swollen than the others. In the 

 very earliest stages it is almost impossible to detect the 

 presence of the parasite by a superficial examination, but 

 the larva, if present, is found on opening the scale. The 

 mature forms of the scale usually exist on the same plant 

 with the immature stages, and if these are seen to contain 

 the parasite then it is fairly safe to deduce that the others 

 are also attacked. Taking the average from a great many 

 plants that 1 liave examined, I iind the proportion of scales 

 destro3ed by the parasite to be very high indeed, for 

 usually almost every scale is killed. My experience is, of 

 course, limited, and is relatively unimportant, for in order 

 to make a reliable statement regarding the proportion of 

 Coccidie destroyed, many months would have to be devoted 

 to collecting evidence and compiling statistics on this point, 

 and my work has been mainly on other aspects of the sub- 

 ject. But as far as I can judge from the facts that have 

 come under my immediate observation, I am led to rate 

 very highly the value of these parasitic Ilymeno'ptera as 

 destroyers of Coccid pests. In the case of Lecanium 

 ]iemisi>]t;i'ricuia, King's statement that it is one of the 

 commonest pests in greenhouses, applies to the neighbour- 



