The Method of Feeding by the Larvae
As has been mentioned, a captive glow-worm which has lowered vertical fishing lines can be fed on flies. The house fly (Musca domestica) is somewhat too large, and it must be stunned or else it will tear away the whole snare. In nature the food consists mainly of midges and Microlepidoptera. The stunned fly was placed at the bottom of the vertical lines, usually two lines being necessary to suspend the fly. After dark, or about an hour after the worm had been offered the fly, the former climbed down the vertical lines, punctured the fly (Pl. 9, Fig. 10), and began to
Fig. 8—Two small rotten boughs pinned together leaving space for hanging snare lines which have been partly tangled owing to the tray not being carefully enough carried from table to the place for photographing (8 p. m.). Fig. 9—The larva descends from its hiding place above to inspect and mend the damage (10 p. m.).
Fig. 10—The larva has pulled up a house fly and is sucking out its juices. The snare has been mostly demolished by struggles of prey, and the dragging up. Inset on right, disturbed by a flashlamp, the larva drops the fly and retreats to its hiding place. Note mucus on carcase of fly. Fig. 11—The suspended pupa in a cavity in a bank at Arapuni. The soil around was crumbling sandy gravel. This was the only pupa found during six months search.
Fig. 12—The larva in Fig. 10 has now suspended itself after clearing away the sticky vertical lines around it. Clearance 20 mm on each side. Fig. 13—Next day it had pupared. The clear ultimate segment, also seen in the previous figure, is, in this photograph, partly covered by the larval exuvia. On the left inset, is a lateral view of another pupa which shows tapered suspensory cord (C) as depicted in Pl. 10, Fig. 13.
turned out. Either by the struggles of the fly, or by the dragging upwards of the fly by the glow-worm, the major local part of the snare is destroyed as in Pl. 9, Fig. 10. Sometimes the fly is found to have been dropped subsequently by the glowworm beneath the snare as in Pl. 9, Fig. 10A, the carcase is shiny, being covered with mucus from the tangled web; eventually over a period of weeks, sucked-out bodies of flies collect beneath the snare. In other cases, if the insect offered had been small enough, the remains of the carcase were found adherent to an outer part of the snare. Before morning the satiated worm had mended the broken snare. The worms were never seen to come down suddenly when the fly was placed on the snare, as happens with spiders, but this may be due to the fact that captive worms were over fed, or were merely cautious. It has been concluded that the larva neither pulls up the lines which have snared the prey by turning its body, nor does it use its mouth parts for this purpose. In all cases observed, the worm stretched down, holding on to various lines undoubtedly by means of the roughened segmental bands on its body, and proceeded to feed. Only after that did it attempt to haul up the snared prey, holding it by its jaws, and as has been pointed out, in doing.
Text-fig. 1.—Fig. 1—Diagram of production of a vertical line. Five lines have already been made, and the larva is holding a sixth just prior to attaching it near the horizontal runway. Fig. 2—The mucus droplet just before inclusion on the vertical line surrounds the larval head, which is then pulled out of the mucus, and the silk line the continued until the next droplet should be placed. Fig. 3—Diagram of suspension of larva prior to pupation. The vertical lines have been cleared away, so as to leave a free area for the eventual emergence of the adult. The suspensory thread is a new production, not the converted runway. Carcases of flies at F.
suck out its juices. If alarmed by the shaking of the table or by the flashlight, the worm retreated (Pl. 9, Fig. 10A) but re-engaged shortly after the light had been so dragged up the tangled local vertical lines as well as the carcase. These remarks refer to well fed worms in captivity. Undoubtedly the worms in caves consume most of the small midges they live on.