Larval Growth and Survivorship of the Black Swallowtail Butterfly in Central New York

Abstract

The objectives of this study were to measure larval growth and mortality rates in a butterfly population and to determine how these rates vary locally in space and time. The survivorship and growth rates of 1353 Papilio polyxenes larvae, placed on natural food plants in typical habitats, were followed during both generations of 1973 and 197 4. In each year and generation, cohorts offirstinstar larvae were set out on three commonly used host-plant species and at two elevations. Larvae reaching the fifth instar were returned to the laboratory, where the surviving pupae gave rise to 87 adults. Together with estimates of egg mortality in the field (50%) and the sex ratio of emerging adults (50/50), this result indicates that females must lay at least 60 eggs, on average, to replace themselves once in the next generation.Stage-specific mortality rates (qx) averaged 0.59, 0.33, 0.35, and 0.41 for the first four instars, respectively, approximating a Type II survivorship curve (constant mortality rate). Both the shapes of survivorship curves and the probability of reaching the fifth instar were highly variable from one treatment to another, however, providing a heterogeneous pattern of survivorship in space and time. Survivorship was greater in 1973 than in 1974, probably due to different weather conditions; it was greater at high-elevation than at low-elevation sites; and it was greater on wild carrot, Daucus carota, and on parsnip, Pastinaca sativa, than on poison hemlock, Conium maculatum. Survivorship oflarvae placed artificially did not differ from that of larvae hatching from wild-laid eggs on the same host species at the same time and place.Arthropod predators attacking larvae included spiders as well as hemipterans of the families Nabidae, Reduviidae, Coreidae, and Pentatomidae. Parasitoids emerging from larvae or pupae belonged to the families Phoridae, Tachinidae, Ichneumonidae, and Braconidae. Our results, supplemented by predator-exclusion experiments in 1977, indicate that predation is the major source of larval mortality, small (arthropod) predators having the greatest impact on younger larvae and large (vertebrate) predators the greatest impact on older stages.Larvae grew faster in 1973 than in 1974, probably because of more favorable weather in 1973. Growth was faster at low-than at high-elevation sites and markedly faster on poison hemlock than on wild carrot or parsnip.Unpredictability oflarval survivorship in space and time is likely to favor widely spaced oviposition by P. polyxenes females. Such behavior may also be favored by variability in larval growth rates, since adult emergence times may be crucial to the reproductive success of surviving male progeny.

Enemy-free space maintains swallowtail butterfly host shift

“…Larval presence͞ absence was noted on all visits to the site, and larvae were measured on days 1 and 6 of development. This treatment ended on day 6 because C. cnidiifolium larvae had reached the fifth instar; hence, all larvae were removed from the bags to complete their development in the laboratory (8). All sites experienced some mortality because of faulty molting (n ϭ 13) or entrapment in Tanglefoot (n ϭ 2), not predation.…”

“…If absent, and Ͼ1 day had elapsed since the previous visit, the date of disappearance was estimated to be the average between those two dates. Fifth-instar larvae were removed from the field to complete development so that the proportion of larvae at each site that had been parasitized by T. l. panzeri could be observed the following spring upon emergence (8). Treatment H: Similar methods were used as for treatment C, but plants were covered with bags that were identical to those used in treatment B, except for the addition of several holes (3-to 15-cm diameter).…”

“…Other swallowtail larvae are subject to attack by a range of invertebrate and vertebrate predators (8,9); my observations over the past 5 years of P. m. aliaska near Fairbanks, AK, suggest that the two most important larval predators are Formica podzolica Francoeur, an ant species that is widely distributed throughout North America (10), and the ichneumonid parasitoid Trogus lapidator panzeri Carlson. Jeffries and Lawton (11) defined EFS as ''ways of living that reduce or eliminate a species' vulnerability to one or more species of natural enemies.''…”

Life History Plasticity: Influence of Photoperiod on Growth and Development in the Common Blue Butterfly

“…However, causes of mortality can vary with size (Dempster 1984, Feeny et al 1985. Kristensen 1994, and it is conceivable that predation by, for instance, vertebrates would increase rapidly if larvae grew beyond their normal size.…”

Using body length measurements to study larval growth: a lepidopteran example

“…Dyar (see Hutchinson & Tongring 1984), one of the most widespread uses of the width of head capsule is for identifying and determining the number of immature instars, although with some restrictions (e.g., McClellan & Logan 1994). On the other hand, body length measurements have been used to evaluate the biomass of insects in "community studies" (Rogers et al 1976, Schoener 1980, Gowing & Recher 1984, Dial & Roughgarden 1995 or, more rarely, to estimate the growth rate of immatures when it is not possible or desirable to weigh them directly (Rausher 1979, Feeny et al 1985, Costa 1991, Denno & Benrey 1997.…”