Life tables and larval dispersal of Mexican bean beetle (Coleoptera : Coccinellidae) on dry bean in the high plains

Survivorship Of experimental cohorts of Mexican bean beetle, Epilachma vari vestis Mulsant, was studied in three commercial dry bean (Phaseolus vulgari s L.) fields in 1995 and 1996 near Scottsbluff, NE. Mexican bean beetle sur vival was relatively low in 1995 but higher in 1996. In 1995, approximate t o 50% of the egg masses did not hatch. The high egg mortality observed was likely related to drought stress of the host plants, because stressed plant s turn their leaves over and expose eggs to sunlight. In 1996, environmenta l conditions were mild compared with 1995, and egg hatch was greater. Morta lity of young larvae was lower than it was in the last two larval stages. T he cumulative mortality ranged from 92.1 to 95.8% in 1995 and from 60.9 to 75.6% in 1996. No parasitized or diseased larvae were observed in the study fields ol in those held for parasitism tests. Larvae from the same cohort (egg mass) were found distributed throughout a maximum range of 3.6 row-met er.