Title: Life History of Delphastus Catalinae: a predator of Bemisia tabaci Authors
Submitted to: Journal of Insect Science
Publication Type: Abstract Only
Publication Acceptance Date: November 9, 2006
Publication Date: February 22, 2008
Citation: Legaspi, J.C., Simmons, A.M., Legaspi, B.C. 2008. Life History of Delphastus Catalinae: a predator of Bemisia tabaci. Journal of Insect Science. 8(4):27 Technical Abstract: Immature development and reproductive life history of Delphastus catalinae (Coleoptera: Coccinellidae) feeding on Bemisia tabaci (Homoptera: Aleyrodidae) immatures was studied at three constant temperatures: 22, 26 and 30 ºC. Development rates and lower temperature threshold temperatures (T0) were estimated at 9 and 9.9 ºC, for males and females, respectively. Thermal units required for immature development was about 300 degree-days in both sexes. As temperature increased from 22 to 30 ºC, immature development time from eggs to pupae declined from 24 to 15 days, and adult longevity ranged from 138 and 77 days. The intrinsic rate of increase r, increased from 0.048 to 0.082 and doubling time DT decreased from 14.44 to 8.45 days as temperature increased from 22 to 26 ºC. Results indicated that Delphastus catalinae was found to perform better at 22 and 26 ºC; 30 ºC was detrimental to immature development and adult reproduction. In a separate experiment, we studied the effect of plant species and insect stages on feeding by predator D. catalinae on B. tabaci. To study the influence of plant species, immature whitefly prey were presented simultaneously to starved predator adults on leaf cuttings of five different plant species: cotton (Gossypium hirsutum), tomato (Lycopersicon esculentum), Hibiscus (Hibiscus rosa-sinensis), cowpea (Vigna unguiculata) and collard (Brassica oleracea). Percentage predation over 24 h was significantly highest on cotton, followed in rank order by collards, cowpea and tomato, and lowest on Hibiscus. Different predation rates may have been caused by differential response to volatile secondary compounds released by the leaf cuttings. Host stage preference was studied by presenting individual adult predators with equal numbers of prey (200 per replicate) in three aggregate life stages: eggs, small nymphs (1st to 3rd instars) and large nymphs (4th to pupae). Significantly higher numbers of eggs were consumed in a 24-h predation period, compared with small or large nymphs. These findings suggest that among the plant species tested, Delphastus catalinae may be most effective on early-season cotton or immediately after whitefly infestation when eggs are predominant.