TypHa Insects: THEIR EcoLoGicaAL RELATIONSHIPS 475 
plants. It is probable that such a migration to the flower spike was 
accidental; on the other hand, it may have been because the. plant had 
a central stalk with a flowering spike that the larvae could not or would not 
enter it, for the writer has never found that they bored into a plant which 
had a flower stalk, nor has he ever found a piant in which the stem borers 
occurred producing a flower stalk. 
- The larvae enter the stalk from behind the sheath after they leave the 
leaf, and there they feed for some time. Only once were two larvae found 
in the same burrow. They normally become solitary borers, tunneling 
through the center of the stem, going downward to the crown, and some- 
times even advancing for a short distance into the rhizome. This tunneling 
causes the central leaves of the plant to die, and consequently no flower 
spike is formed. The affected plants are easily recognized by the presence 
of the dead central leaves. 
The larvae grow rapidly and by late fall have attained a length of 
nearly two inches. ‘They leave the burrow full of the frass and the shreds 
of the fibrous tissue torn loose by their passage. In the fall, before the 
larvae go into hibernation, they eat out an exit hole in the stem, four to 
six inches above the ground, which they loosely plug up with frass and 
fibrous material. They then make a little compartment, or cell, by 
closing the burrow above and below with a mass of frass and fibrous 
material, as shown in Plate XLI, 27 and 28, and thus pass the 
winter. If one visits the marshes in winter and opens the plants, the 
larvae are found in the burrow, completely surrounded by ice. Larvae 
taken to the laboratory during September and October and placed in 
metal salve boxes on moist, sterilized sand, pupated in February and 
March. Adults emerged from sixteen to twenty days later. Larvae 
brought into the laboratory in the spring pupated much later, as is shown 
by table 5. 
In the laboratory, several days before the larva transforms to the pupal 
stage, it begins to spin a thin, irregular layer of fine thread all over the 
surface of the sand in the salve box. In the field, one finds these loose 
webs lining the burrows in the stalks. The larva then becomes very 
sluggish and gradually shortens until it seems only about half of its normal 
length. The shiny, almost black, larval skin becomes much lighter in 
color. This is a sign that pupation will occur within twenty-four to 
