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The function of multiple mating by female promethea moths, callosamia promethea (drury) (lepidoptera: saturniidae).

INTRODUCTION

Unlike the case for multiple mating in males, the benefits of polyandry are more puzzling. Research has focused on the direct and indirect benefits and costs to females who pursue multiple mating (Drummond, 1984; Thornhill and Alcock, 1983; Eberhard, 199B; Simmons and Siva-Jothy, 1998; Jennions and Petrie, 2000; Torres-Vila et al., 2004). Some functions proposed to favor polyandry include insuring an adequate sperm supply, minimizing physiological costs of long-term sperm storage, enhancing female survivorship or reproduction through food gifts or nutrition derived from spermatophores, increasing genetic diversity within a female's progeny and minimizing loss of time and energy required to resist insistent males (Drummond, 1984). Mate choice studies of species with multiple mating in females tend to highlight genetic benefits accrued by females' offspring (e.g., Jennions and Petrie, 2000). Another area of interest, centered on sexual conflict, highlights the 'reduction of male harassment' function of polyandry and evolutionary consequences (reviewed in Arnqvist and Rowe, 2005; Chapman, 2006). Research into the functions of polyandry often highlight one or two of the possible functions (e.g., reduction of male harassment: Arnqvist, 1989; good or compatible genes: Brown, 1997; Zeh and Zeh, 1997; Tregenza and Wedell, 1998; insuring adequate sperm supply: Gromko et al., 1984; nuptial gifts: Gwynne, 2008).

It is important to study a diversity of species to establish how life history traits underlie the evolution of polyandry and to establish in what circumstances a given function might be more important to the evolution of polyandry than another. Here, I test some of the general ideas to explain the evolution of female multiple mating in a genus of silk moths (Callosamia) that shows variation in this trait.

None of the ca. 1480 species of silk moths in the family Saturniidae have been studied in relation to polyandry because it is generally thought that they are uniformly monandrous (W. Oehlke, pets. comm.). Thus, my discovery that female Callosamia promethea, the promethea moth, mate multiple times was unexpected. I show here that multiple mating is rare or nonexistent in the closely related, C. angulifera, the tulip tree moth (a third North American member of this genus, C. securifera, does not occur at my study area).

Silk moths have comparatively simplified adult life history traits in which to explore the costs and benefits of polyandry. Saturniid adults rely on energy for reproduction derived exclusively from larval feeding. Adults do not eat so mating cannot entail costs from lost feeding time. Also, most of a female's eggs are mature upon eclosion ('ovigeny index' = 1, Jervis et al., 2005; but see Miller et al., 1983) so there is no tradeoff between egg maturation and other fitness variables (Jervis and Ferns, 2004). In an ultimate sense, females are in control of when and how often they mate because they can choose, or not choose, to call in males for copulations using male-attracting pheromones alone (e.g., Mayer, 1900; Rau and Rau, 1929; Tuskes et al., 1996). A noncalling female is 'invisible' to males. Therefore, avoiding male harassment is not involved in this case of polyandry.

Calling females might attract several males but there is no evidence that they actively choose mates from among them (pers. obs.; see Tuskes et al., p. 16); they accept the first male to reach them and then cease calling. It is a clear case of "first come, first served" and males have evolved to get there first, not to compete directly with other males for access to females (Collins and Weast, 1961). Males have been attracted from as far as 33 km (Toliver and Jeffords, 1981) so mate choice by females appears to be random and calling is not an example of indirect mate choice (Wiley and Poston, 1996). Female saturniids usually mate and lay eggs nocturnally and, in this circumstance, mating conflicts with time that could be spent egg laying. The tulip tree moth's schedule follows this common saturniid mating and ovipositing pattern; however, the promethea moth mates diurnally and lay eggs nocturnally, eliminating this conflict (Collins and Weast, 1961). If the copulation vs. egg laying time constraint is true, then tulip tree moths should be monandrous.

Here, I test experimentally two hypotheses about the function of polyandry in promethea moths. First, I ask whether multiple mating increases fertility and, second, whether it increases fecundity.

METHODS

STUDY ANIMALS AND SITE

The study site is located in NW Pennsylvania (41[degrees]47'N, 79[degrees]57'W) on 150 ha of largely forested land owned by The Hemlock Hill Field Station. A description of the site can be found in Morton (2005). In Jan., 2005, I collected wild promethea cocoons from which I kept six females. These females were mated once, placed in brown paper grocery bags for egg laying (Tuskes et al., 1996, p. 46) and, from Jun.-Aug. 2005, I raised 105 promethea larvae from these eggs. The six larval broods were raised separately within remay cloth sleeves (2.29 m long and 1.70 m in circumference) tied over different branches of the same black cherry tree (Prunus serotina). The cocoons were numbered individually and kept at ambient temperature in a screened porch (2.4 m high x 2.8 m wide x 6.6 m long) attached to a house during the winter of 2005-06. Larvae of tulip tree moths were hatched from 10 eggs obtained from a commercial source in 2004 (www.silkmoths.bizland.com) and raised in sleeves on local tulip trees (Liriodendron tulipifera) that summer. Three female tulip tree moths were mated to wild males in 2005 and 36 overwintering cocoons were available for hatching in spring, 2006.

In May 2006, 96 promethea cocoons from five sibling groups (one sibling group had eclosed during Aug. 2005, instead of overwintering as pupae) were attached individually with duct tape and a staple to the tips of 35 cm twigs held by gravel in open topped quart canning jars. Each sib group, identified here by the number on the mother's cocoon, occupied its own jar (Table 1). The jars were set on a sill along one end of the screened porch. Female promethea moths eclosed in the morning and remained on and called from their cocoons between 1500-1830 h on day of hatching. The females were never placed in cages. Instead, jars with female(s) calling from their cocoons were moved to a bench just outside the screened porch until the female(s) was in copula and then brought back inside the porch. No pairs broke up due to this handling. I recorded the time copulation began and when the copulating pair separated.

In Jun.-Jul., 2007 male moths emerging from captive raised cocoons and wild males successful in copulating were individually numbered (underside of left hindwing) with fast drying liquid "white out." I searched for marked males on subsequent afternoons when they were attracted by female calling. My purpose was to see how often males copulate. Polyandry might evolve to compensate for low fertility in multiple mating males (Torres-Vila and Jennions, 2005; Lauwers and Van Dyck, 2006).

Tulip tree moth cocoons, like promethea, were overwintered in a plastic box with a screened top (to protect them from rodent predation), but, unlike the promethea, were kept in the container until they eclosed. In nature, cocoons fall to the ground when the tulip tree leaf enclosing them abscises (Tuskes et al., 1996). Emerging female tulip tree moths climb a substrate to allow expansion of wings and later fly to higher perches before beginning to call. Because tulip tree moth mating is nocturnal and not cocoon based, I placed females individually in a hardware cloth cage (openings 1.5 by 4 cm, permitting copulation by wild males through the cage) and video recorded their mating behavior from ca. 2030-0230 h with a Sony Digital8 Handycam using the Night Shot 0 lux feature. During daylight hours females were placed in a paper bag then returned to the cage for video taping at 2030 h on their second night to ascertain whether they mated again.

EXPERIMENTS ON PROMETHEA

To compare fertility and fecundity, the first female to eclose from each sibling group was designated to be single or double mated by coin toss. Thereafter, I alternated between mating frequency as females emerged within each sibling group. The numbers of females in each mating category for each sibling group are listed in Table 1. Upon emergence each female was observed for calling, a conspicuous behavior (see Fig. 1 in Tuskes et al., 1996). The jar holding the calling female clinging to her cocoon was placed outside the porch where males could reach her. When in copula, the jar, now with a pair clinging to the cocoon, was brought inside the porch. When the pair separated, the time was noted and the male was preserved in 95% alcohol in a glass vial and placed in a freezer for later analysis of paternity sharing. The female was put in a paper bag labeled with her cocoon's number. The next morning, between 0900 and 1100 h, the number of eggs laid the previous night in the bag was tallied and each night's clutch thereafter was circled with a different colored marker to keep them separate. A new bag was used whenever needed. This was done daily for each female until she died. At 1300 h each female was removed from her bag and placed back upon the cocoon from which she had emerged. Females chosen for multiple copulations were carried outside and brought back inside the porch when mating, as described for their day of emergence. Females designated monandrous were allowed to call normally, but left inside the porch. Handling of both monandrous and multiply mated females was the same so that they differed only in number of copulations. All females extruded their scent glands, whether virgin or nonvirgin, before obtaining copulations. One female escaped after laying 133 eggs so was removed from the data set for number of eggs laid.

[FIGURE 1 OMITTED]

When a female died, she was placed in 95% alcohol and frozen if she had been multiply mated. Each female's daily clutches of eggs were cut from the paper bags and placed together in a separate plastic container for each female. When hatching began, each egg was examined for a given laying date. Those that hatched were considered fertile and those that did not hatch were dissected under a compound microscope for the presence of an embryo. Eggs with no development were considered infertile. For doubly mated females, each brood of hatchlings was preserved in 95% ethanol and frozen for later paternity analysis.

An index to female body size was obtained by dissecting out the inner cocoon that had contained the pupa from the outer cocoon envelope. Inner cocoons are hard, thin walled and approximate the shape of a prolate spheroid. I used calipers (accurate to 0.1 mm) to measure the length and width of the inner cocoon and calculated its volume using the formula 4/[pi]a[b.sup.2], where a = length and b = width. I used the web-based ABE volume calculator for a prolate spheroid. Eggs were saved after hatching and later measured using a compound microscope fitted with an ocular micrometer accurate to 0.001 mm. I only measured the width of eggs, sampling 10-20 eggs laid during the first or second clutch and a similar sample laid near the end of the laying period, because hatching obliterated the egg's length. Laying period comprises the number of days between the laying of the first and last clutch of eggs.

STATISTICS

Data were analyzed with the JMP SAS statistical package (Sall et al., 2005) using Oneway ANOVA, t-tests, or Wilcoxon signed-rank tests depending upon normality of data. Significance was set at [alpha] = 0.05 and two-tailed tests were used throughout. Standard error of the mean (SE) was used as a measure of dispersion.

RESULTS

FERTILITY

Mean number of eggs laid for the sibling groups combined was 249.6 [+ or -] 6.1 (Table 1) with a range of 190-324 eggs. The mean actual number of infertile eggs per female was 5.1 [+ or -] 1.5. This average was low, 2% for all females combined. Fertility did not differ between females mated once or twice either for all females (t-test assuming unequal variances, d.f. = 20, t = -1.0797, P < 0.15) or when divided into individual sibling groups (Oneway ANOVA, d.f. = 34, F = 0.4206, P < 0.79). Thus fertility was not affected by the number of times a female mated. Egg infertility did not increase towards the end of the laying period, as might be predicted if sperm was in short supply in single mated females, nor did infertility increase with the total number of eggs laid (ANOVA, d.f. = 34, F = 0.5422, P < 0.49).

FECUNDITY

A significant difference in the number of eggs laid was found between females mated once and twice (Fig. 1; one copulation, mean = 237.3 [+ or -] 6.7 eggs; two copulations, mean = 260.1 [+ or -] 9.2; t-test assuming unequal variances, (d.f. = 34, t = -2.0056, P < 0.05). I tested this finding for robustness by looking at several subsets of the data, including possible effects of sibling group, eclosion date, female size, egg size, copulation durations and egg laying period, to see if these affected the positive relation between number of copulations and fecundity.

Sibling groups differed in the mean number of eggs laid (ANOVA, d.f. = 34, F = 4.4719, P < 0.005). Group 8 laid significantly fewer eggs than the others and group 40 laid more eggs than groups 19 and 8. Due to high egg fertility, fecundity was positively related to the number of eggs a female laid (logistic regression between number of eggs laid and eggs hatched, d.f. = 34, [r.sup.2] = 0.97, P < 0001). Number of eggs laid was significantly related to the inner cocoon volume index to female body size (ANOVA, d.f. = 34, F = 9.1564, P < 0.005) and cocoon volume differed significantly between sibling groups (ANOVA, d.f. = 34, F = 5.8736, P < 001). Groups with the larger females laid more eggs than those with smaller females resulting in the significant difference between groups. However, female size did not contribute to the significant increase in fecundity with multiple mating because monandrous and polyandrous females were distributed randomly within each sibling group (Table 1). An ANOVA comparing female size (cocoon volume) with number of copulations showed no relationship (d.f. = 35, F = 1.6287, P < 0.21).

[FIGURE 2 OMITTED]

The size of eggs did not differ among sibling groups (ANOVA, d.f. = 35, F = 0.2954, P < 0.88). However, egg width declined for every female during her laying period, averaging 1.611 [+ or -] 0.056 mm for eggs in her first or second clutch vs. 1.466 [+ or -] 0.014 mm for eggs in her penultimate or last clutch. This was highly significant using a paired design (Wilcoxon Signed-rank test, d.f. = 34, test statistic = 315.0, P < 0.0001). The relation between egg widths with successive days in the laying period was not determined. Egg size was not related to number of copulations (P < 0.67). Interestingly, the sibling group with the smallest females, group 8, laid significantly more eggs in their first clutch than the other groups (ANOVA, d.f. = 35, F = 7.6161, P < 0.002; Table 1). When the number of eggs laid in the first clutch was regressed against cocoon size for the entire sample a significant negative relation was revealed (ANOVA, d.f. = 36, F = 6.3905, P < 0.02). In terms of the percentage of the total numbers of eggs laid, the seven smallest females laid an average of 38% of their total eggs the first clutch (range = 8-61%) whereas the seven largest females laid an average of 17% of their total eggs in their first night (range = 2-38%). Smaller females, regardless of sibling group, laid more eggs in their first clutch. Subsequent clutches did not differ significantly in number of eggs laid (Fig. 2). Miller et al., (1983) found that 52 promethea moths laid 85% of their total number of eggs laid in the first three clutches. My sample of promethea laid 57% of their total eggs in their first three clutches, a significantly smaller percentage than Miller et al., (1983) found (d.f. = 85, t = 2.2545, P < 0.05). I found no difference in the number of eggs laid in the first three nights for my sample comparing females that were mated once or twice (t-test assuming unequal variances, d.f. = 35, t = 0.4443, P < 0.33). There was also no relationship between sibling group and the number of eggs laid in the first three clutches (ANOVA, d.f. = 4, F = 1.7218, P < 0.17). Sibling groups did not differ in the number of days their members laid eggs (ANOVA, d.f. = 33, F = 0.7304, P < 0.58). As did Miller et al., (1983) I found no relation between the number of days in which females laid eggs and the number of eggs they laid (ANOVA, d.f. = 33, F = 0.3535, P < 0.60).

Sibling groups did not differ in copulation duration (ANOVA, d.f. = 34, F = 1.2142, P < 0.33). However, the second copulations for twice-mated females were significantly shorter than their first copulation (first and second copulations averaged 271.2 [+ or -] 10.2 min vs. 231.2 [+ or -] 10.0 min; Wilcoxon Signed-rank test, d.f. = 15, test statistic = 49.0, P < 0.01). This difference was due to the time in the afternoon when females began calling: a female's second copulation began on average 97 [+ or -] 32 min later than her first copulation, which was a significant difference (Wilcoxon Signed-rank test, d.f. = 15, test statistic = -55.000, P < 0.01).

MATING IN TULIP TREE FEMALES

Ten tulip tree moth females eclosed during the morning between 25 Jun. and 7 Jul. 2006. All were mated the night or early morning following emergence between 2200 and 0130 h. None mated again when set outside in cages the evening following their day of eclosure. Instead they laid eggs upon the cage wire.

PROMETHEA MALE CHOICE OF MATE

Male time to arrival after one female began calling was studied on 2 d separated by 1 wk. First males arrived 7 and 10 rain after calling began in the two tests and were captured before they reached the female. The next males arrived 14 and 18 min later, respectively, which is sufficient time for the first males to have been in copula had they not been captured (Morton, unpubl, data). Often, several females were calling, separated by less than a meter. For example, on 4 Jul. 2006 there were 15 calling females either virgin, calling for second matings outside the porch, or inside the porch if they were to remain single mated. Additional males attracted by still calling, unmated females, sometimes found and attempted to separate a newly in copula pair outside the porch by beating them with their wings. None of these attempts was successful in dislodging the mating male once he covered the tip of his female's abdomen with his glove-like terminal genital claspers (n = 16 observations of such attempts) (see Koshio et al., 2007).

Males appear able to distinguish between calling virgin and calling nonvirgin females and pair first with virgin females. Nonvirgin females were sometimes unsuccessful in obtaining copulations when set out along with virgin females, but the same females were successful when there were no virgins to "compete" with (n = 4). Female 24 called for 3 h next to 3 virgins who all mated. One male came by her, but did not mate. The next day, female 24, with no virgins calling, was copulating at 1605 h. She also mated the next day, again with no virgins present. Similarly, nonvirgin females 42, 83 and 92 were unsuccessful in attracting males when three virgins were calling, all of which mated. The next day, with only one virgin female to compete with, these nonvirgin females mated.

From 2 Jun. through 12 Jul. 2007, 65 males were marked and released, of which 33 were captive raised and marked before release on their day of emergence and 32 were wild males marked following copulations with captive raised females. Unsuccessful wild males attracted to calling females were not marked. Of the 33 captive raised males, five (15%) copulated with captive raised females within 2 d of their date of eclosure and release. Fourteen wild and captive raised males successful in copulating were seen on subsequent afternoons (22%) and six of these nonvirgin males copulated with virgin females (9%). I conclude that multiple mating by males (polygyny) is not uncommon. The time between marking and last resighting of marked males averaged 2.9 d (range = 2-4 d), including the day they were marked. This suggests either males disperse widely or their life span is short compared to females.

DISCUSSION

Promethea moths are polyandrous with females mating for several afternoons following their emergence from cocoons. I allowed females randomly chosen for polyandry to mate only two or three times, so the average number of copulations obtained by females under natural conditions is unknown. However, one female I allowed to mate every time she called did so every afternoon for 5 d from 3-8 Jul. Polyandry did not affect fertility because females allowed to mate twice did not exhibit greater fertility than females forced to mate monandrously. However, polyandrous females laid 10% more eggs and so achieved higher fecundity than females allowed only a single copulation (Fig. 1).

I examined factors other than mating frequency that could underlie this difference in fecundity. I eliminated genetic differences as a factor by testing fecundity among randomly chosen females from five sibling groups. Their mothers were mated once so they were full siblings. I raised their larvae in separate sleeves on the same food plant to control for differences in intraspecific plant suitability (Michaud, 1990; Scriber et al., 1991). I found that polyandrous females did not lay eggs for a longer period than monandrous females. Larger females laid significantly greater numbers of eggs and size differed among sibling groups but this effect was controlled for in the experimental design and was not associated with differences in number of copulations. Miller et al., (1983) also found a high correlation between body size and total eggs, but their egg total average, 182, was much lower than in my study (219-275 eggs, Table 1), perhaps because their data were based upon dissection of females rather than a count of eggs laid. Miller and Cooper (1977) showed a decline in fertility from 94.1 to 71.8% during the first seven days of the egg laying period for 28 female promethea moths mated once. The average number of eggs laid per female in their study was only 170, suggesting their females were small due to underfed larvae. I found no decline in egg fertility with laying date and my sample averaged 98% fertility. Egg size was, likewise, not affected by number of copulations. Adult longevity was not associated with egg production; the same results found by Miller et al., (1983).

Duration of copulation was not associated with fecundity, but, because nonvirgin females began calling later in the afternoon, their second copulations were shorter than their first. Virgin females had a competitive edge over nonvirgins because males clearly preferred virgins for mating. Perhaps nonvirgin females began calling later as a means to avoid competition with virgins for mates when males are in short supply because of the male preference for virgins. The male preference is likely due to the fact that virgins have more ovules to fertilize than nonvirgins because the latter have already laid at least one clutch of eggs. Sperm competition is also a likely factor in this preference. The fact that some virgin females might have mated with nonvirgin males was not reflected in lower fertility rates in monandrous compared to polyandrous females.

Although egg size was not related to copulation frequency, all females laid eggs that were 10% smaller towards the end of their egg laying period compared to the beginning. Diminishing egg size may be adaptive if this allows more eggs to pack into the ovary. Diminishing egg size may represent a tradeoff between putting the 'best' eggs out first and predation if the chance of being preyed upon increases with time. Smaller hatchlings from late eggs should survive less well than their larger, earlier, siblings if this offspring quality hypothesis is true. However, if predation probability increases with time, then why don't females lay more eggs early? There is much variation in egg laying rate that is not understood (Fig. 2). For instance, why is size related to a higher egg laying rate in small promethea moths? The small females in my study laid 38% of their eggs in the first clutch whereas my largest females laid only 17%. There may be a tradeoff between predation, egg laying rate and dispersal from the natal area with smaller females opting for laying eggs quickly if they do not have the energy reserves needed for dispersal. Dispersal would favor females who do not lay eggs as quickly as they could and dispersal may be important in avoiding build up in parasitoid populations (Peigler, 1977).

This is the first study of polyandry in a wild saturniid silk moth. This group has life history traits that eliminate some costs found in other species. Adult silk moths do not feed, for example, so there can be no conflict between feeding and mating. Females control male mating behavior, becoming 'visible' to males only when producing pheromones and they can become 'invisible' quickly by retracting their 2 mm scenting gland. Males rapidly lose interest in searching for them when they do this (pers. obs.). Mating may be costly if it increases predation but, for promethea moths, copulation may provide safety for females. Males, but not females, mimic distasteful butterflies (Sternburg et al., 1977; Jeffords et al., 1979) and may provide protection from bird predation for the female through their close association during copulation. Batesian mimicry and complex innate behaviors exhibited by promethea moths suggest that predators are a major source of selection (Evans, 1978). Most of a female's eggs are mature and ready for fertilization when she ecloses, eliminating sperm storage costs. Because of these traits, a female silk moth has been viewed as having two priorities--to lay her eggs as quickly as possible and to act as a dispersal mechanism.

If costs to mating are low in the promethea moth, why isn't polyandry reported for more species of silk moths? It appears likely that a time constraint on egg laying accounts for the apparent rarity of polyandry. Mating, which consumes several hours, and egg laying are competing uses of time because both occur nocturnally in the vast majority of species, although flight times for egg laying could differ from mating times even in nocturnal saturniids (W. Oehlke, pers. comm.). Support for the time constraint hypothesis is provided by my comparison with the promethea moth's congener, the tulip tree moth (Peigler, 1981; Johnson et al., 1996), which is completely nocturnal and lacks polyandry. Tulip tree moths were observed laying eggs during the same time period in which they were copulating the previous evening on their day of eclosure.

Further tests of the importance of the time constraint hypothesis are possible. For example, the third North American species in this genus, Callosamia securifera, like the promethea moth, mates diurnally, usually between 1000 and 1400 h, and lays eggs at dusk (Brown, 1972; Tuskes et al., 1996). This species, like promethea, has very dark males suggesting Batesian mimicry. Similarly, other silk moth species with diurnal mating, such as Eupackaria calleta, which calls and mates from ca. 0730 until noon (Tuskes et al., 1996) are predicted to be polyandrous if the time constraint hypothesis is important. An egg laying time constraint has been suggested for other Lepidoptera as well (Forsberg and Wiklund, 1989).

The effect of polyandry in promethea on genetic variation cannot be evaluated here, although the adult females, their mates and their offspring were preserved for later analysis. If polyandry increases the genetic diversity of a female's offspring, greater resistance to disease is likely (see Hughes and Boomsma, 2004; Seeley and Tarpy, 2007). Greater resistance to disease via polyandry is supported by the ease with which promethea moth larvae are raised in captivity compared to larvae of the monandrous tulip tree moth, which more often succumb to viral or bacterial disease under "crowded" conditions (pers. obs.; Tuskes et al., 1996). It is noteworthy that the promethea has the widest geographic range of the three species and is polyphagus whereas the others are monophagous (Peigler, 1976). The degree to which polyphagy is promoted by genetic variability in Callosamia deserves attention (Scriber and Slansky, 1981; Scriber et al., 1991).

The higher fecundity of my polyandrous female promethea moths strongly suggests that they obtained more than sperm from male ejaculates (Gwynne, 2008). Miller et al. (1983) found 20% of eggs were immature at emergence in promethea so it is possible that the 10% increase in total eggs laid by polyandrous females is due to an enhancement of development of these immature eggs. Successive oocytes in an ovariole of the closely related cecropia moth (Hyalophora cecropia) mature more slowly and decline in size as depletion of two yoke proteins occurs (Telfer and Rutberg, 1960). This limitation of yoke proteins with successive oocytes may explain why promethea eggs become smaller as the laying period nears its end. If 20% of a female's eggs continue to mature following her emergence (Miller et al., 1983), nuptial gifts might somehow enhance her ability to provide yolk spheres, which contribute more than 90% of egg volume (Telfer and Rutberg, 1960) to later oocytes. If promethea polyandry provides females with seminal gifts, the only form of post larval nutrition possible for a saturniid moth, polyandry should be more common in silk moths. That polyandry is uncommon, suggests that the time constraint between mating and oviposition usually overrides such a hypothetical nutritional benefit.

Acknowledgments.--The author is grateful to his wife, Bridget, and children, Douglas and Sarah, for their sacrifice of a living space and tolerance during the summer of 2006. I also thank Bridget Stutchbury, William Oehlke and J. Mark Scriber for providing reviews and to our students, especially Tobin Macintosh, for obtaining paper bags.

SUBMITTED 3 MARCH 2008

ACCEPTED 21 APRIL 2008

LITERATURE CITED

ARNQVIST, G. AND T. NILSSON. 2000. The evolution of polyandry: multiple mating and female fitness in insects. Anita. Behav., 60:145-164.

--AND L. ROWE. 2005. Sexual conflict. Princeton University Press, Princeton, New Jersey. 330 p.

BROWN, L. N. 1979. Mating behavior and life habits of the sweet-bay silk moth (Callosamia Carolina). Science, 176:73-75.

CHAPMAN, T. 9006. Evolutionary conflicts of interest between males and females. Current. Biol., 16:R744-R754.

COLLINS, M. M. AND R. D. WEAST. 1961. Wild silk moths of the United States. Collins Radio Co., Cedar Rapids, Iowa. 138 p.

DRUMMOND, B. B. 1984. Multiple mating and sperm competition in the Lepidoptera, p. 547-572. In: R. L. Smith (ed.). Sperm competition and the evolution of animal mating systems. Academic Press, London.

EBEHARD, W. G. 1996. Female control: sexual selection by cryptic female choice. Princeton University Press, Princeton, New Jersey. 501 p.

EVANS, D. L. 1978. Defensive behavior in Callosamia promethea and Hyalophora cecropia (Lepidoptera: Saturniidae). Am. Midl. Natur., 100:474-479.

FORSBERG, J. AND C. WIKLUND. 1989. Mating in the afternoon--time-saving in courtship and remating by females of a polyandrous butterfly Pieris napi L. Behav. Ecol. Sociobiol., 25:349-356.

GWYNE, D. T. 2008. Sexual conflict over nuptial gifts in insects. Ann. Rev. Ent., 53:83-101.

HUGHES, W. O. AND J. J. BOOMSMA. 2004. Genetic diversity and disease resistance in leaf-cutting ant societies. Evolution, 58:1251-1260.

JEFFORDS, M. R., J. G. STERNBURG AND G. P. WALDBAUER. 1979. Batesian mimicry: field demonstration of the survival value of pipevine swallowtail and monarch color patterns. Evolution, 33:275-386.

JENNIONS, M. D. AND M. PETRIE. 2000. Why do females mate multiply? A review of the genetic benefits. Biol. Rev., 75:21-64.

JERVIS, M. A. AND P. N. FERNS. 2004. The timing of egg maturation in insects: ovigeny index and initial egg load as measures of fitness and of resource allocation. Oikos, 107:449-461.

--, C. L. BOGGS AND P. N. FERNS. 2005. Egg maturation strategy and its associated trade-offs: a synthesis focusing on Lepidoptera. Ecol. Ent., 30:359-375.

JOHNSON, K. S., D. SNIDER AND J. M. SCRIBER. 1996. Estimates of genetic differentiation among Callosamia species and Hyalophora cecropia (Saturniidae) using allozyme electrophoresis. J. Lepid. Soc., 50:217-225.

KOSHIO, C., M. MURAJI, H. TATSUTA AND S. KUDO. 2007. Sexual selection in a moth: effect of symmetry on male mating success in the wild. Behav. Ecol. doi: 10.1093/beheco/arm017. LAUWERS, K. AND H. VAN DYCK. 2006. The cost of mating with a non-virgin male in a monandrous butterfly: experimental evidence from the speckled wood, Pararge aegeria. Behav. Ecol. Sociobiol., 60:69-76.

MAYER J. G. 1900. On the mating instinct in moths. Psyche, 9:15-20.

MICHAUD, J. P. 1990. Conditions for the evolution of polyphagy in herbivorous insects. Oikos, 57:278-279.

MILLER, T. A. AND W. J. COOPER. 1977. Oviposition behavior of colonized Callosamia promethea (Saturniidae). J. Lepid. Soc., 31:282-283.

--, -- AND J. W. HIGHFILL. 1983. Egg production in female Callosamia promethea (Lepidoptera: Saturniidae) as a function of pupal size and adult longevity. Ann. Ent. Soc. Am., 76: 668-670.

MORTON, E. S. 2005. Variation in breeding habitat use in the Ovenbird with special reference to breeding habitat selection in northwestern Pennsylvania. 2005. Wilson Bull., 117:327-344.

PEIGLER, R. S. 1976. Observations on host plant relationships and larval nutrition in Callosamia (Saturniidae). J. Lepid. Soc., 30:184-187.

--. 1977. Parasitism of Callosamia. J. Georgia Inst. Soc., 12:111-114.

--. 1981. Demonstration of reproductive isolating mechanisms in Callosamia (Saturniidae) by artificial hybridization. J. Res. Lepid., 19:72-81.

RAU, P. AND N. L. RAU. 1929. The sex attraction and rhythmic periodicity in the giant saturniid moths and its relation to the function of reproduction. Trans. Acad. Sci. St. Louis, 26:83-221.

SALL, J., L. CREIGHTON AND A. LEHMAN. 2005. JMP start statistics: a guide to statistics and data analysis using JMP and JMP IN software. Thomson, SAS Inst. Inc., Toronto, Ontario.

SCRIBER, J. M., J. POTTER AND K. JOHNSON. 1991. Lack of physiological improvement in performance of Callosamia promethea larvae on local host plant favorites. Oecologia, 86:232-235.

--AND F. SLANSKY. 1981. The nutritional ecology of immature insects. Ann. Rev. Ent., 26:183-211.

SEELEY, T. D. AND D. R. TARPY. 2007. Queen promiscuity lowers disease within honeybee colonies. Proc. Royal Soc. B, 274:67-72.

SIMMONS, L. W. AND M. T. SIVA-JOTHY. 1998. Sperm competition in insects: mechanisms and the potential for selection, p. 341-434. In: T. R. Birkhead and A. P. Moller (eds.). Sperm Competition and sexual selection. Academic Press, San Diego, California.

STERNBERG, J. G., G. P. WALDBAUER AND M. R. JEFFORDS. 1977. Batesian mimicry: selective advantage of color pattern. Science, 195:681-683.

THORNHILL, R. AND J. ALCOCK. 1983. The evolution of insect mating system. Harvard University Press, Cambridge. 547 p.

TELFER, W. H. AND L. D. RUTBERG. 1960. The effects of blood protein depletion on the growth of the oocytes in the cecropia moth. Biol. Bull., 118:352-366.

TOLLIVER, M. E. AND M. R. JEFFORDS. 1981. Long distance dispersal by Callosamia promethea (Saturniidae).J. Lepid. Soc., 35:76.

TORRES-VILA, L. M. AND M. D. JENNIONS. 2005. Male mating history and female fecundity in the Lepidoptera: do virgin males make better partners? Behav. Ecol. Sociobiol., 57:318-326.

--, M. C. RODRIGUEZ-MOLINA AND M. D. JENNIONS. 2004. Polyandry and fecundity in the Lepidoptera: can methodological and conceptual approaches bias outcomes? Behav. Ecol. Sociobiol., 55:315-324.

TUSKES, P. M., J. P. TUTTLE AND M. M. COLLINS. 1996. The wild silk moths of North America. Cornell University Press, Ithaca, New York. 250 p.

WILEY, R. H. AND J. POSTON. 1996. Indirect mate choice, competition for mates, and coevolution of the sexes. Evolution, 50:1371-1381.

EUGENE S. MORTON

Department of Biology, York University, Toronto, Ontario M3J 1P3, and Hemlock Hill Field Station, Cambridge Springs, Pennsylvania 16403

Corresponding author: telephone: 814-398-4787; e-mail: mortone@si.edu
TABLE 1.-Characteristics of female promethea moth sibling groups used
in mating study

                Number mated   Number mated       Total number
Sibling group     one time      two times          eggs laid

      8              4              5         219 [+ or -] 10.74SE
     19              4              4         261 [+ or -] 10.74
     26              2              1         263 [+ or -] 17.54
     40              5              6         275 [+ or -] 10.13
     47              3              4         234 [+ or -] 11.48

                  Number eggs
Sibling group   in first clutch

      8         99 [+ or -] 10.6
     19         29 [+ or -] 10.6
     26         49 [+ or -] 17.2
     40         37 [+ or -] 9.4
     47         31 [+ or -] 11.3
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Author:Morton, Eugene S.
Publication:The American Midland Naturalist
Article Type:Report
Geographic Code:1USA
Date:Jul 1, 2009
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