Development of Tribolium castaneum on resistant starches

The development of Tribolium castaneum, red flour beetle (Coleoptera: Tenebrionidae), on six different types of starches was examined and compared to flour. Particle size distribution of the six starches was characterized. Each of the starches (5g) was infested with 50 T. castaneum eggs and held in a growth chamber at 28°C and 65% RH. Larval weight, length, and head capsule width were checked every three days for one month. These three parameters of T. castaneum on starches were smaller than those on control group (flour) and positive control group (flour with 5% yeast). Larval mortality on Fibersym® RW and potato starch increased significantly from 22.0% on day 9, to 100% on day 15, and from 37% on day 9, to 100% on day 21, respectively. The weight larvae gained on flour was 16 fold more than that on Hylon VII and 91 fold more than that on Fibersym® RW. These results suggest that resistant starch hinders T. castaneum development. The particle size of starches used in this research was between 15µm to 58µm, compared to 133µm of flour. This indicates particle size was not a limiting factor for T. castaneum to digest the starch. The obstruction was either the lack of protein and lipid in pure starches or the characteristic of resistant starch that escapes enzymatic hydrolysis or both. In addition to development of T. castaneum on resistant starches, research of relative retention and fecundity of T. castaneum on starches is currently taking place in our laboratory.