19°/.] 



Insect, Fungous and Other Pests. 



159 



down any hard-and-fast rule about wasps and their harmfulness. 

 In general terms it may be said that in bad wasp years, i.e., in 

 years when wasps are abundant, the nests should be destroyed. 

 Whether a year is likely to turn out a bad wasp year or not 

 will depend to a large extent on the character of the preceding 

 spring. On the return of warm spring weather the queens 

 which have been hybernating issue from their winter quarters, 

 each to act as the foundress of a new colony. If the spring be 

 an early one and the weather remain genial, then the year will 

 be likely to show more than the usual abundance of wasps. 

 If, however, there be some genial weather early in the year a 

 certain number of queens will be tempted out from their winter 

 shelter-places, and if severe weather or wet, cold weather follow, 

 a number of these will perish, i.e., unsettled weather in spring 

 with renewed alternations of warm and cold or dry and wet 

 weather will mean a greater mortality of queens, and the 

 number of wasps in the summer will vary accordingly. 



When wasps' nests are to be destroyed, this may be done by 

 the use of bisulphide of carbon, 1 oz. of which should be poured 

 into the hole, if this be in the ground, and the hole then stopped 

 up in the way suggested for the treatment of ants. 



Snow Fly. — A note on Snow flies appeared in this Journal 

 in June, 1904, and specimens of Brussels sprouts and tomatoes 

 infested with these insects, which are also termed Ghost flies 

 and White flies have recently been received from Moreton-in- 

 Marsh and Louth. Snow flies (Aleyrodes) belong to the same 

 order as aphides and scale insects. The progress of the attack 

 is usually from the lower leaves upwards. Although the flies 

 breed in winter as well as in summer, they are most abundant 

 in the late summer and early autumn. When mature they 

 look like powdery moths. 



Snow flies are sometimes most harmful to the cabbage and 

 allied species, but they are common both under glass and in the 

 open. The damage is done by the insect in its various stages 

 draining the sap from the leaves by means of a proboscis or beak 

 which it pushes below the surface. Where the leaves are badly 

 infested they should be pulled off and burned ; they should not 

 merely be thrown aside, for the complete life-cycle of an indi- 

 vidual does not take long and may even be completed on leaves 

 thrown aside if they are fairly fresh. Any of the sprays or 



