Biology and seasonal occurrence of Manduca quinquemaculata and M. sexta (Lepidoptera: Sphingidae) in southwestern Michigan

The seasonal occurrence and development of field populations of Manduca quinquemaculata (L.) and Manduca sexta (Haworth) were monitored at the Kellogg Biological Station in Barry County, Mich., from late June to early September during 1985 and 1986. Results indicated that initial and peak oviposition were variable between years for both species and were not predictable by accumulated degree-days (DD), base 10 degrees C. In both years, initial egg deposition occurred slightly earlier for M. quinquemaculata than for M. sexta (DD 615 versus DD 728 in 1985 and DD 700 versus DD 742 in 1986), whereas peak oviposition was dependent upon the year in question. In 1985, oviposition for M. quinquemaculata peaked approximately 100 DD earlier than for M. sexta. In 1986, the reverse was observed. Larval development occurred at the same rate in both species and was closely associated with degree-day accumulation requiring, on the average, 39 DD per stadium. Monitoring data from both years indicated that M. quinquemaculata is likely univoltine in Michigan whereas M. sexta is probably bivoltine.