64 H. W. Peal — Monograph of the Oriental Aleurodidze. [No. 3, 



examined for fine details. Those species which have the dorsum 

 covered with spines should be mounted under a cover glass raised 

 above the slide by a cork or metal ring. The cover glass is thus kept 

 some distance from the insect itself. It is impossible however in this 

 case to examine with very high powers. The winged insect should 

 be mounted as soon as possible, as it is impossible to make out the 

 details in a shrivelled specimen. I find Canada balsam excellent for 

 mounting them, but it is advisable to stain some of the insects first. 

 It will be found somewhat difficult to mount the adult so as to show 

 the wings to advantage. I find that by placing the insect on the slide, 

 when the balsam is somewhat hardened, gentle pressure on the head 

 with a fine pin will cause the body to slip backwards and leave the 

 wings spread out evenly. If this is found difficult, an alternative 

 method is to carefully cut off the wings with a fine scalpel, the operation 

 meanwhile being watched with a hand lens. As a rule it will be found 

 that Canada balsam is not suited for those species in which, the wings 

 are banded, as the bands show but faintly. In this case mount dry 

 by making a ring of balsam and after placing the wing in the centre, 

 pressing on a small cover glass. Keep a fairly large number of the 

 insects in situ on the dry leaves and also some of the winged insects in 

 empty phials or if preferred in spirit. 



CHAPTER III. 



Preventive Measures. 

 I do not think it will be out of place to describe shortly such pre- 

 ventive measures as are useful in eradicating or at any rate keeping 

 down these pests. These insects cannot be killed by means of any 

 of the poisons ordinarily used against mandibulate insects, as they 

 exist by pumping up sap from within the leaves by means of their 

 setae. The most convenient all-round remedy is the well-known kero- 

 sine emulsion which when sprayed on the plants kills the insect by 

 closing up the spiracles. It is true that these insects are extensively 

 parasitized by chalcids and their numbers thus kept down ; but despite 

 this check these pests often get out of hand and do extensive damage. 

 The causes which lead to this result are varied. It may be that as in 

 the case of most cultivated plants, their natural food-plant may be large- 

 ly increased and thus sufficient pabulum be provided ; or seasons may 

 be favourable. In this case the pests' increase would be short-lived, 

 as the parasite being provided with plenty of food, would soon increase 

 and reduce the pest to something like its old numbers. If, however, 

 the pest is unwittingly imported with its food-plant into a new country 

 and its natural parasite or parasites be left behind at home, it is possible 



