IO2 PAUL S. WELCH. 



were removed from their burrows and placed on other leaves; 

 also whenever it was necessary to restock the large tank, which 

 served as the aquarium, by introducing larvae from the field. 

 In about 40 per cent, of these cases the larvae bored into the petiole 

 without any preliminary cutting of the leaf while others cut slits 

 leading directly towards the attachment of the petiole. With the 

 beginning of the petiole period comes the restriction of a single 

 larva to each leaf. 



Length of the Burrows. The length of the burrow in the petiole 

 varies according to the time it has been inhabited, and to some 

 extent according to the size of the larva. Burrows were frequently 

 two feet long and occasionally longer. Sometimes the burrow 

 extended down to the rootstalk but no instance was observed in 

 the field in which the burrow extended into it. There seems to 

 be no reason why this should not occur since it will be shown 

 later that the substance of the rootstalk can be used as food. 



Deserted Burrows. Burrows of various lengths were often 

 found which had been constructed and then deserted without 

 apparent cause. These burrows ultimately collapsed to some 

 extent and became brownish on the inside. Usually they were 

 inhabited by other aquatic animals, such as gyrinid larvae, crus- 

 taceans (amphipods), chironomid larvae, small aquatic coleoptera, 

 .and small leeches. 



Formation of New Burrows.- In order to observe the initial 

 'steps in the production of a new burrow, larvae 4.3/2 cm. in length 

 were removed from the petioles and placed in the aquarium on 

 fresh, uninfested leaves. Some took to the leaves and began 

 boring from the upper side of the leaf into the petiole while 

 others attacked petioles which happened to be nearly horizontal 

 and only partly under water. The larva began excavation by 

 biting into the tissue until the mouth was full; then the head was 

 withdrawn and the mass expelled at the margin of the hole. 

 This was continued until the head was buried after which time 

 the larva ate the tissue removed. Microscopical examination of 

 the initial material deposited around the margin of the hole showed 

 that it was merely pulverized leaf tissue. 



Other Points of Attack. Occasionally peduncles were found 

 both in the field and in the aquarium which had been attacked. 



