I9 1 !♦] Aphides, or Plant Lice. 



833 



APHIDES, OR PLANT LICE.* 



Nearly all plants, both in garden and field, and under glass, 

 suffer from the ravages of Aphides. These universal pests are 

 most common in temperate climates, but even in the tropics 

 whole crops are ruined by them. Aphides are known by a 

 variety of common names, such as Plant-Lice, Green or Black 

 Fly, Smotherers, or Dolphins, while the disease they cause is 

 sometimes termed ''Blight." 



Aphides are soft-skinned insects with antennas generally 

 longer than the body. When wings are present they are 

 delicate, and have few veins. On the upper surface of the 

 abdomen two tubes are generally present — sometimes short, 

 sometimes long — from which a liquid can be discharged. The 

 mouth parts are fitted for piercing and sucking; the plant 

 tissues are first pierced and then the sap is drawn away. The 

 skin of plant-lice is provided with glands which secrete a 

 waxy or mealy substance or woolly masses which have the 

 power of throwing off water. 



The young differ little in form from the full-grown insects, 

 and their feeding habits are the same. 



Development from the young stage to adult takes a very 

 short time, and hence multiplication of individuals is rapid. 

 Dry, hot weather is specially favourable for Aphides. 



The summer generations of Aphides are produced without 

 the presence of males, and the females may be wingless or 

 winged, both conditions being found in the same life-history. 

 The winged generations spread the infestation. These 

 females — wingless and winged alike — can give rise to live 

 young, and this power of viviparous multiplication and the 

 appearance of winged forms are to be associated with abund- 

 ance of food at certain times of the year. As the cold part of 

 the year comes males as well as females are produced and 

 fertilised eggs are laid. 



Some Aphides confine themselves to one species of plant ; 

 others migrate so that part of the life-cycle is spent on a plant 

 of a different species. Migration of the same kind of Aphid 



* Various species of Aphis are dealt with in Leaflets issued by the Board, copies 

 of which can be obtained on application, viz. : Woolly Aphis (Leaflet 34), Currant 

 Aphides (Leaflet 68), Hop Aphis (Leaflet 88) and Aphides or Plant Lice (Leaflet 104). 



