The silk proteins made by aquatic larvae of the midge, Chironomus tentans, fall intothree size classes. There are four giant (r1000 kD) proteins, spIa-d. Extracts of C. tentans salivary glands showed two SDS-resistant complexes, C1a and C1b, by non-denaturing agarose gel electrophoresis each of which contained spIs plus other silk proteins. Conventional shadowed EM preparations showed discrete lattice-like structures. Very preliminary STEM data indicate that while these thin lattice-like structures are barely visible above background, they have masses of several thousand kD. In addition to mass measurements, these proteins have a large number of cystines (r100) which might be interesting to gold label. While this project has barely begun, it appears that the STEM will be able to help determine the role of these complexes in the assembly of silk fibers.