Recently, it has attracted much attention that a single neuron displays highly sophisticated integration process that is characterized by active membrane properties including voltage-gated calcium channels. Here we have focused on the information processing of nociceptive thermal stimuli in Class IV dendritic arborization neurons (Class IV neurons) that are somatosensory nociceptor neurons of Drosophila larvae. To perform in-depth analyses, we built a new measurement system that combines three components: infrared laser that allows step-like and local heating, calcium imaging, and extracellular recording. We found that Class IV neurons exhibited a specific firing pattern that were accompanied with calcium spikes against noxious thermal stimuli, which induced intermittent pause periods after high frequency firing trains. Our genetic analysis showed that the heat sensitivity of Class IV neuron was mediated by two TRPA channels (Painless and dTrpA1), and that a L-type calcium channel (Ca-α1D) was essential for the generation of the calcium spikes. We assume that calcium spikes generate the "burst and pause" pattern, through which Class IV neurons transmit the noxious heat inputs. Drosophila larvae depend on the activity of Class IV neurons to sense both thermal and optical stimuli, but generate distinct behavioral outputs. Interestingly, noxious light stimulation increased firing frequency, but did not accompany pause periods. These results suggest that the calcium spike can be a key signal encoding a specific modality: The continuous firing train transmits the noxious light sensation; in contrast, the pause after high-frequency firing does the noxious heat input.