Action of douglas fir tussock moth larvae and their microflora on dietary terpenes.

A single type of bacterium, tentatively identified as a member of the genus Bacillus, was isolated from 2 of 20 midguts of Douglas fir tussock moth larvae being fed a diet of fir needles. No bacteria could be isolated from most midguts. Although spherically shaped bodies were present in the food bolus, these bodies, if microorganisms, could not be distinguished from spherical bodies associated with the plant tissue. The Douglas fir tussock moth dietary terpenes were altered during their passage through the insects, with two new terpenes being detected in the feces. One of these was identified as isoborneol. The relative significance of the insect and gut microflora with respect to terpene modification is unresolved. The well-established toxicity of terpenes may account for the near absence of common gut microflora in the insects.