Regeneration of appendages in the large milkweed bug, Oncopeltus fasciatus

An analysis was made of the regeneration of legs and antennae of Oncopeltus. Amputations were performed on first instar larvae within 24 hr after hatching, and on later instars within 24 hr after ecdysis. The resulting regenerates were then measured at each instar. When amputations were performed soon after hatching, there was no significant effect on the duration of any instar. The regenerate was usually visible after the second post-operative ecdysis, and was smaller than a normal appendage (hypomorphic). Removal of the three distal segments of the antenna usually resulted in regeneration of only one segment which was abnormally long and showed a combination of the bristle patterns characteristic of the two most distal segments of the control. In a few such cases a partial intersegmental membrane was present in the regenerated segment. Removal of the tarsus resulted in a structurally complete regenerate which was smaller than the control tarsus. The largest leg regenerates were obtained when amputation was performed through the tibia. With amputation through the femur, a decrease in length of the remainder of this segment was observed after the first ecdysis. This type of amputation and amputation through the trochanter in some cases resulted in the formation of a globular stump containing tarsal claws. The results indicate that amputation of part of an appendage in Oncopeltus does not stimulate an increased growth rate in the stump, but merely causes reorganization of the stump material which subsequently grows at the normal rate. Since even the most hypomorphic regenerates contained well-formed claws, even though proximal parts were missing, it appears that the reorganization process must begin at the most distal point and proceed proximally.