BRANCH ARTHROPODA; CLASS JNSECTA : THE INSECTS 201 



time to time. These winged plant-lice fly away to new 

 plants. In the autumn a generation of males and females 

 is produced ; these individuals mate and each female lays 

 a single large egg which goes over the winter, and pro- 

 duces in the spring the wingless agamic stem-mother. 

 Plant-lice produce honey-dew, a sweetish substance much 

 liked by ants, and the lice are often visited, and sometimes 

 specially cared for, by the ants for the sake of this honey- 

 dew. Small as they are, plant-lice occur in such numbers 

 as to do great damage to the plants on which they feed. 

 The apple-aphis, cherry-aphis, pear-aphis, cabbage-aphis 

 and others are well-known pests. The most notoriously 

 destructive plant-louse is the grape PJiylloxera, which 

 lives on the roots and leaves of the grape-vine. Im- 

 mense losses have been caused by this pest, especially in 

 the wine-producing countries of southern Europe. 



Diptera : the flies. TECHNICAL NOTE. Obtain specimens 

 of the adult and young stages of the blowfly and the mosquito. All 

 the young stages of the blowfly may be obtained, and its life-history 

 studied, by exposing a piece of meat to decay in an open glass jar. 

 The larvae of the mosquito are the familiar wrigglers of puddles 

 and ponds, and by collecting some of them and keeping them in a 

 glass jar of water covered with a bit of mosquito-netting, the life- 

 history of the mosquito is easily studied. If the eggs can be ob- 

 tained from the pond so much the better ; they are in little black 

 I masses floating on the surface of the water, and resemble at first 

 j glance nothing so much as a floating bit of soot. The external 

 structure of the adult flies should be compared with that of the 

 other insects studied, noting especially the condition of mouth-parts 

 and wings, and the substitution of balancers for the hind wings. 

 The mouth-parts of the mosquito are in the form of a long proboscis 

 composed of six slender needle-like stylets lying in a tube narrowly 

 open along its dorsal surface. The tube is the labium, and the 

 stylets are the two maxillae, two mandibles, and two other parts 

 known as the epipharynx and the hypopharynx. Two additional 

 thicker elongate segmented processes lying outside of and parallel 

 with the tube are the maxillary palpi. The male mosquito (distin- 

 guished from the female by the more hairy or bushier antennae) lacks 



In taking care to provide a constantly abundant supply of food. This ex 

 it was continued for more than lour years. 



