Figure 4.

Effects of Epsom salt on the growth and development of coconut rhinoceros beetle (CRB). Epsom salt was added to the rearing mulch at 1×, 2×, and 5× the manufacturer’s recommended rate for palms and the development of CRB was monitored from egg to adult. (A) The addition of Epsom salt significantly delayed the development of larvae into second and third instars but did not significantly impact the duration of the third-instar or pupal phase. (B) Larval weight gain was reduced with increasing concentration of Epsom salt in the mulch. (C) Adult biometrics were negatively impacted by the presence of Epsom salt during larval development, resulting in noticeably smaller adult beetles (D). Epsom salt at the 5× rate was lethal to CRB larvae, and therefore the results of this treatment are not shown in any parts of this figure. Data with different letters or numbers are significantly different (life stage duration: first instar, F_2,52 = 11.39, p < 0.001; second instar, F_2,52 = 4.16, p < 0.05; third instar, F_2,51 = 1.114, p = 0.336; pupa, F_2,50 = 2.91, p = 0.122; adult biometrics: weight, F_2,50 = 23.434, p < 0.001; length, F_2,50 = 21.839, p < 0.001).