THE FEEDING HABIT OF TERMITE CASTES AND ITS RELATION TO THEIR INTESTINAL FLAGELLATES

¹ Fellow (in the Biological Sciences) of the National Research Council, working at the Department of Medical Zoölogy, School of Hygiene and Public Health, Johns Hopkins University, Baltimore, Maryland

All results were obtained from laboratory colonies which have been carefully studied during the past three years. Many of these results have been verified by field observations.

At every stage in the life-cycle of any caste where wood is eaten, protozoa are present. When wood is not eaten or obtained in some way, protozoa are never present.

Second and third form young adults have lost the ability to eat wood. The protozoa in these castes disappear concomitantly with the loss of the ability of their host to feed on wood, and by the time the wood-eating ability is lost, they have all disappeared. This occurs about the time of the final molt and is perhaps brought about by the feeding of salivary secretions which take the place of the wood diet. In all castes, the protozoa are lost during molting, but they are soon regained, except in the final molt of the second and third forms, in which forms they are never regained because, owing perhaps to the degeneration of their jaw muscles, these forms have lost the ability to eat wood. What causes the jaw muscles to degenerate is not definitely known. It may be inherent in these castes, as much a part of them as anything else. If it is, then the salivary-feeding is hereby made necessary and takes the place of the wood diet when the jaw muscles degenerate. But a more plausible possibility is that these forms are fed so much salivary secretion that they cease to feed on wood and because of this their jaw muscles degenerate through disuse, and thus the ability to feed on wood is lost forever.

The first form and the worker always eat wood, except in the post-adult stage of the life-cycle of the first form, where it, too, after having attained an old age loses the ability to eat wood and becomes dependent on the workers and young undifferentiated nymphs (when present) which it has reared. It is noteworthy that mostly workers are raised in the first brood.

Adult soldiers, owing to their large mandibles, cannot eat wood (cannot chew it), though they obtain it, together with protozoa from the ani of the xylophagous members of the colony. Soldiers, like workers, harbor protozoa throughout. their lifecycle. Young soldiers (soldier nymphs), before they obtain the large mandibles, can chew wood for themselves. So can the second and third forms, during early life.

A caste which cannot eat wood, or, thinking in terms of the protozoa, a caste which does not harbor protozoa, cannot live by itself. Such individuals are dependent on the wood-eating members of the colony for support; consequently adults of the second form, third form, and soldier castes must be supported by other members of the colony. But the soldiers, in one sense, are not as difficult to support as the second and third forms, since they can digest for themselves the partially digested woody material which has passed through the alimentary canal of the xylophagous members of the colony before they receive it; while the second and third forms, since they feed exclusively on the salivary secretions, must subsist entirely on predigested food.