Abstract

Spruce budworm larvae have 2 sugar-sensitive cells, one in the lateral styloconic sensillum (LST) of the galea and one in the L1 sensillum of the maxillary palp, indicating the importance of sugars to these insects. Several sugars, such as sucrose and fructose, are important phagostimulants. In fleshflies, two sites are responsible for binding with sugars, a pyranose (P) site that binds pyranose sugars (i.e. glucose), and a furanose (F) site that binds furanose sugars (i.e. fructose). The LST of spruce budworms responds to both pyranose and furanose sugars. In the present study it was found that, unlike the LST, the L1 sensillum in sixth instar larvae does not respond to any of the pyranose sugars tested. Furthermore, the L1 response to sucrose and fructose differed from that of the LST. This indicates that the two sugar-sensitive cells may have differences in the sites (P- and F-) that they possess.