Abstract
The cardiograms of the dorsal vesssel in intact insects were obtained with the three methods devised by the author. Although the pulse-frequency in larvae usually fluctuates regularly, an irregular fluctuation ranging from 15 to 19 per minute followed by pausing for a period of 7.2 to 16.2sec was observed in the 3rd instar larvae of Xylotrupes dichotomus. In pupae and adults of Dendrolimus spectabilis and several other species, the fluctuations were observed in sequence of the following three phases: a rapid phase continuing for 73.6sec in an average with beating 60-86 per minute in pupae, or for 74.9sec with 100-200 beating in adults; a rest phase, for 10.9sec without beating in pupae or 17.1sec in adults; a slow phase, for 46.7sec with 5-40 beating in pupae, or 44.8sec with 5-30 in adults. This regularity in fluctuation was not affected by light conditions, but disturbed by the movements of the insect body; viz., a temporary shortening of duration or lacking of a certain phase occurred. In the immature pupae of Dendrolimus spectabilis shortly after pupation, the rest phase was not detected. No artifacts caused by the insertion of an electrode into the insect body were observed on the cardiograms.
