Simple SummaryIn Mexico, the red spider mite,Tetranychus merganser, is one of the most economically important pest mites in papaya crops, causing damage to the fruits and leaves. This research aimed to assess the effect of five host plants (Carica papayaL. (papaya),Capsicum annuumvar.glabriusculum(Dunal) Heiser and Pickersgill (chili piquin),Helietta parvifolia(Gray) Benth. (barreta),Phaseolus vulgarisL. (bean), andRosa hybridaL. (rosebush)) on the biology and life table parameters ofT. merganser. We hypothesized thatT. merganserhas a better biological performance on papaya than on other host plants. The results of this research can be used to develop management and control strategies forT. merganser. The mean immature period of red spider mite females was longer on barreta leaf disks than on chili piquin, rosebush, papaya, and bean. The oviposition ofT. merganserwas greater on bean disks than on the other host plants. Host plants affect the number of eggs laid by the red spider mites, which reduce their intrinsic rate of natural increase. The demographic parameters suggest the unsuitability of barreta as the host for the development of red spider mites, and the best performance ofT. merganserwas onP. vulgaris.AbstractThe quality of the host plant affects the life history parameters of tetranychid mites. The biology and fertility life tables ofTetranychus merganseron five host plants (Carica papaya,Phaseolus vulgaris,Capsicum annuumvar.glabriusculum,Helietta parvifolia, andRosa hybrida) were assessed under laboratory conditions at 28 ± 1 °C and 70–80% relative humidity (RH) with a photoperiod of 12:12 h (L:D). The development period of immature females differed among the tested host plants and ranged from 9.32 days onP. vulgaristo 11.34 days onH. parvifolia. For immature males, it ranged from 9.25 days onP. vulgaristo 11.50 days onH. parvifolia. The female survival rate varied from 53.97% onH. parvifoliato 94.74% onP. vulgaris. The highest total fecundity rate was recorded onP. vulgaris(125.40 eggs/female) and the lowest onH. parvifolia(43.92 eggs/female). The intrinsic rate of increase (rm) varied from 0.271 (H. parvifolia) to 0.391 (P. vulgaris). The net reproductive rate (RO) was higher onP. vulgaristhan on the other host plants. The longest mean generation time (GT) was calculated onC. annuumvar.glabriusculumand the shortest onRosa hybrida. The demographic parameters suggest the unsuitability ofH. parvifoliaas the host for the development of red spider mites, and the best performance ofT. merganserwas onP. vulgaris.