Chemoreception of sucrose and amino acids in second and fourth instars of the spruce budworm Choristoneura fumiferana (Clem.) (Lepidoptera: Tortricidae)

We examined the responses of some gustatory neurons in various contact-chemoreceptor sensilla of second-instar larvae of the spruce budworm. These included the L1 and L2 sensilla on the maxillary palp, and the LST and MST sensilla on the galea. Our objective was to determine whether there were differences in the physiological characteristics of individual neurons between the early and late larval instars. Changes were observed in both some sugar-sensitive and amino acid-sensitive neurons. We also confirmed the presence of a water-sensitive neuron in the L2 sensillum. Our findings are discussed in relation to changes that occur during the development of both the host plant and the insect. To our knowledge, this is the first paper to examine the responses from contact-chemoreceptor sensilla of very young second-instar caterpillar larvae.