Some species of "cylindrical bark beetles" or Colydiidae feed solely on decaying vegetable matter, but a number are predaceous on wood-inhabiting beetles, and some are ectoparasitic. Bothrideres geminatus Say is a predator of mature larvae or pupae of several Cerambycidae, and in one case several larvae were found within a pupa of Chrysobothris sp. In the latter development was presumably internal (Craighead 1920). Hopkins (cited by Clausen, 1940) recorded B. contractus as an external parasitoid of Cerambycidae larvae. Bothrideres cactophagi Sc. is parasitic on prepupae of the large cactus weevil, Cactophagus validus. Deretaphrus oregonensis Horn was found in pupal cells of Asemum atrum Esch. in pine, the host larvae being full grown before death (Craighead 1920). The mature larva of this parasitoid is very much modified because of its host relationships (see Clausen, 1940 for diagram). The body is fleshy, fusiform and wide in the mid-abdominal area. It has a thin integument which is glabrous. Mandibles are triangular and forked at the apex, and the ventral mouthparts are fleshy and weak. The legs are short, weak and widely separated. Spiracles occur on the 2nd thoracic and 1st 8 abdominal segments. The dorsum of the 9th segment has a pair of chitinous recurved hooks (Clausen 1940/62).
Dastarcus helophoroides Fairm. is an external parasitoid of the mature larvae of Xylocopa appendiculata Smith in China (Piel 1938). The 1st instar larva is elongated, indistinctly segmented and without spines or setae and has minute rudimentary legs. Development is completed in ca. 4 days. These larvae were found on hosts that had been killed by mites and were already undergoing decomposition, so that is was uncertain whether they were parasitic or scavengers. Clausen (1940) believed that the form of the larva would indicate that they were parasitic.
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