THE DOCK FALSE-WORM. 15 



In collecting these wintering larvae in the spring it was observed 

 that when a larva bored into the side of a stem it always formed 

 its pupal cell below the entrance, unless the stem lay in a horizontal 

 position, when it might go either way. In nearly all cases, but not 

 invariably, the head of the larva lies toward the entrance, so that 

 escape may be facilitated. Where the insect is common, more than 

 one larva will frequently be found in one stem, and sometimes as 

 many as four, or five, or even eight. It sometimes happens that a 

 larva in forming its cell pushes the lower plug down too tightly on 

 the larva below, with the result that the latter is killed. 



The pupa is able to wriggle about in its cell to some extent but does 

 not force its way out to the entrance when the adult is ready to 

 emerge, as is the case with many wood-boring insects. Several hours 

 before emerging the legs, mandibles, and labrum become somewhat 

 freely movable, with the strengthening of the adult muscles within. 

 After casting the pupal skin the adult sometimes lies in its cell for a 

 day or two, especially if the weather is unfavorable (fig. 1, b). It 

 escapes through the original entrance, biting a hole in the cap. If 

 two or more adults are confined in a single vial for several days after 

 emergence they often mutilate each other, sometimes biting off all 

 the appendages. 



The adult flies are quite active and take flight readily. They spend 

 their time flying and crawling about ov.er the larval food plants and 

 the neighboring vegetation, and it is unlikely that they get very far 

 from their birthplace, unless carried by the wind or some other 

 agency. Copulation has not been observed, although numbers of 

 pairs were under observation in breeding jars. No food was observer! 

 to be taken, except that the adults occasionally lapped up the little 

 moisture that occurred on the leaves. 



The female usually oviposits from the upper side of the leaf, and 

 the egg appears below, very close to the epidermis, in a raised blister 

 about 1.2 mm. long. The ovipositor (fig. 3, c, and fig. 5) is thrust 

 into the leaf and gradually worked around to one side by a sawing 

 motion until a nearly circular cell is cut between the upper and lower 

 leaf epidermis. When this is completed, the ovipositor is slowly re- 

 moved as the egg is deposited. In eight timed ovipositions the op- 

 eration occupied from 25 to 75 seconds, with an average of 45 sec- 

 onds. Frequently the eggs are laid in chains, the female after laying 

 one merely moving forward a little and depositing another. Ovipo- 

 sition ordinarily begins within a day after emergence and continues 

 for several days, the majority of eggs, however, being deposited the 

 first two or three days. 



PARTHENOGENESIS. 



Parthenogenesis— that is, the production of young from unferti- 

 lized eggs — has long been known to occur among the sawflies, and the 

 males are ordinarily less common than the females. This partheno- 



