THE MARGUERITE FLY. 31 



its own side. It should be added, however, that the flies will often en- 

 gage in this operation at other times than soon after mating. 



Mating takes place, as a rule, in the forenoon — becoming less frequent 

 towards noon — and during the latter part of the afternoon. Mating 

 between about noon and the latter part of the afternoon is not very 

 common on days of bright sunlight. On cloudy days it continues unin- 

 terruptedly. 



As has already been intimated, couples isolated on leaves on plants in 

 the laboratory were observed mating in artificial light. 



As might be expected, the males are polygamous and the females poly- 

 androus; that is, a male will fertiUze more than one female, and a female 

 will accept more than one male. The number of matin gs during adult 

 life is probably large, and continues, it would seem, throughout the greater 

 part of the same. A female confined with one male at a time within a 

 cheesecloth bag upon a leaf on a plant accepted two males four times in 

 three days, one of the males twice in as many days, and the other twice in 

 one day. In another instance, a couple which had separated at 9.40 a.m. 

 were coupled again at 2.40 p.m. of the same day, although during tliis 

 second coupling the female was very restless, moving about considerably, 

 as if she was not at all contented to receive him. As regards how long 

 mating continues, there is a record of a female which emerged April 13 

 receiving a male May 22, forty days after emergence and seven days before 

 her death; in another instance, a female which emerged April 10 was 

 observed mating May 13, tliirty-four days after her emergence and six 

 days before her death. 



Feeding. 



The females, at least, feed during their adult life, the food being the 

 juices of the leaves of the host plants. To this end the epidermis of the 

 leaf is pierced and the parenchyma in contact with it at that point is cut 

 or macerated by means of the tubular ovipositor. 



The process forms a prominent feature of the female's activity, and is 

 an interesting one to watch. Having selected the site — she often tests 

 the leaf surface with the ovipositor — and placing herself lengthwise upon 

 the leaf or leaf-lobe, so that her longitudinal axis is parallel with the lon- 

 gitudinal axis of the leaf or leaf-lobe, she flexes the apical portion of her 

 abdomen downward and forward so that it approaches the leaf surface 

 vertically. The epidermis is then pierced, and the ovipositor, which is but 

 sUghtly exserted wliile it pierces the epidermis, is inserted into the leaf 

 horizontally. Then, by means of a series of motions of the ovipositor in 

 longitudinal, diagonal, and sometimes transverse directions, involving the 

 alternate protrusion and partial retraction of the ovipositor, and accom- 

 panied by a rotary motion of the abdomen, the parenchyma in contact 

 with the epidermis is cut or macerated. The apical portion of the abdomen 

 is, as a rule, angulated somewhat during the latter part of the operation. 



