Author
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Legaspi, Jesusa |
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LEGASPI, JR, BENJAMIN - STATE OF FLORIDA |
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Submitted to: Environmental Entomology
Publication Type: Peer Reviewed Journal Publication Acceptance Date: 4/19/2005 Publication Date: 10/2/2005 Citation: Legaspi, J.C., Legaspi, Jr, B. 2005. Life table analysis for Podisus maculiventris immatures and female adults under four constant temperatures. Environmental Entomology. 34(5):990-998. Interpretive Summary: The spined soldier bug, Podisus maculiventris, is a common insect predator in North America. It is found in various habitats and crops such as vegetables, grape vineyards, soybeans, alfalfa, and is known to feed on over 75 insect prey species. This species is also mass-reared by biological control companies and is popularly sold in commercial greenhouses, especially in Europe. Scientists at the Center for Medical, Agricultural and Veterinary Entomology located in Tallahassee, FL, studied the predation, development and reproduction of this predator to optimize its use in mass rearing and augmentation in field conditions. Immature and adult P. maculiventris were fed with the greater wax moth larvae, under the following constant temperatures: 18, 22, 26 and 30 ºC. We found that the immatures consumed a mean of about 8 prey larvae at all the temperatures. Body weights were higher at higher temperatures but females were only heavier than males at the last immature stage. The eggs hatched sooner at higher temperatures. The total numbers of eggs laid per female ranged from 429.4 at 18 ºC to 755.4 at 26 ºC. For mass rearing purposes, the optimum temperature tested to rear P. maculiventis is 26 ºC and older females (over 21 days) should not be used because the their eggs may be infertile. Technical Abstract: Detailed life tables and reproduction were studied in nymphs and adult females of Podisus maculiventris (Say) (Heteroptera: Pentatomidae) fed larvae of Galleria mellonella larvae (L.) (Lepidoptera: Pyralidae) at constant temperatures of 18, 22, 26 and 30 °C. Development rates were fitted to the equation Y = a + b ln x. The theoretical development threshold was calculated as To = exp (-a/b) resulting in To = 12.48 ºC; and 12.78 ºC for females and males, respectively. Degree-days for development ranged from 233.92 in males at 18 ºC to 338.73 in females at 30 ºC. In all temperature treatments, P. maculiventris immatures consumed a mean of about 8 prey items. Mean immature body weights were higher at higher temperatures, but females were heavier than males only at the 5th instar. In adult female P. maculiventris, age at first ranged from 2.7 days at 30 ºC to 13.4 days at 18 ºC. Percentage of egg hatch was lowest at 18 ºC (11%) and highest at 30 ºC (36.4%). Survivorship curves showed a linear decline with time, the steepest curves at the highest temperatures. Total number of eggs laid per female ranged from 429.4 at 18 ºC to 755.4 at 26 ºC. Mean egg numbers were fitted to a surface equation as eggs = (-6.658 + 0.432T) d exp (-0.002Td) where d and T are age (days) and temperature (ºC), respectively. Net and gross reproductive rates were highest at 26 ºC (Ro = 379.126; GRR = 491.273 female/female) and lowest at 18 ºC (Ro = 207.873; GRR = 294.972). Generation and doubling times were shortest at 30 ºC (T = 35.021 and DT = 4.270 days). Intrinsic and finite rates of increase were also highest at 30 ºC (r = 0.1623; Lamda = 1.1763). Reproductive parameters were recalculated using numbers of eggs that actually hatched, resulting in lower values although the effects of temperature did not change. In the context of mass rearing P. maculiventris, 26 ºC is the optimal temperature tested, but female predators >21 days should be not be used because they may not be capable of laying viable eggs. |
