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The regal fritillary (''Speyeria idalia'') is a striking nymphalid butterfly found among some of the remaining tallgrass and mixed-grass prairies in the east-central United States. This prairie-specialist butterfly has a characteristic deep orange color and unmistakable dark hindwings with two bands of spots (Brock 2003). On the female, both bands of spots are white. However, on the male, the outer band of spots is orange in color. Females also tend to be slightly larger than males. The ventral surface of the hindwings is olive brown to black in color with bold silvery white spots (Selby 2007). The wingspan of ''S. idalia'' usually measures (Selby 2007). Flight is in the summertime from approximately June to September and adults tend to be swift in flight, coasting close to the ground (Brock 2003). Regal fritillary larvae are approximately 0.08 inches long after they hatch and reach a length of approximately 1.75 inches when fully developed (Edwards 1879). The mature larvae have a black body with yellowish-orange bands and stripes. There are yellowish middorsal and lateral stripes and a number of dorsal, subdorsal, and lateral fleshy spines extending from the body. The head of the mature larvae is rounded and small, orangish-red on top and black underneath (Edwards 1879). The larval food source for the regal fritillary and all members of the genus ''Speyeria'' are violets (''Viola'' spp.) (Selby 2007). The violets are an extremely important component of habitat sustainability for the regal fritillary and there is a correlation between the number of violets present and the number of butterflies found in a given area (Kelly and Debinski 1998). Violet species that the larvae feed on include ''Viola pedata'' (bird’s-foot violet), ''V. pedatifida'' (blue prairie violet), ''V. papilionacea'' (common blue violet), ''V. lanceolata'' (lance-leafed violet), ''V. nuttallii'' (Nuttall’s Violet) (Kelly and Debinski 1998), ''V. sagittata'' (arrowleaf violet), and ''V. tricolor'' (Johnny Jumpup) (Selby 2007). These various violet species are associated with the different areas of the regal fritillary’s range. For example, the bird’s-foot violet and the prairie violet tend to be the preferred larval food source for the regal in the Midwest and Great Plains regions (Selby 2007). The adult butterflies may feed on a variety of nectar plants and their availability throughout the summer flight time can be as important as the presence of larval food plants in determining whether an area can support populations of butterfly species (Selby 2007). Milkweeds, thistles, coneflowers, blazing-stars, bergamots, clovers, goldenrods, and ironweeds are some of the most important nectar sources for adult regal fritillaries. Milkweeds and thistles have been observed to be the preferred nectar source throughout the regal fritillary’s range (Selby 2007). These two types of plants provide a constant supply of nectar due to their staggered growth times. Common milkweed starts blooming when male regal fritillaries begin to emerge early in the summer and thistles tend to bloom later in the season which is crucial to females approaching oviposition (Selby 2007). ==Reproduction and life cycle== The regal fritillary is univoltine, having a single generation per year (Selby 2007). Adult male butterflies emerge in early June along with the first milkweed plants. Adult females emerge shortly after and mating takes place in late June and early July. After mating, females enter a 6 to 8 week period of reproductive diapause, or a suspended period of development. The ovaries remain undeveloped during this time. Oogenesis does not initiate until late August when juvenile hormone sharply increases (Kopper et al. 2001). Once oogenesis takes place, the eggs are fertilized and soon after, oviposition occurs. The female lays over 1,000 eggs and possibly more than 2,000 (Vaughan and Shepherd, 2005). The small larvae hatch in late September and into October. Immediately after hatching, the tiny larvae seek protective covering in the leaf litter and overwinter there. At this stage the larvae delay development over the winter months and this is known as larval diapuase (Kopper et al. 2001). Once spring arrives, the larvae emerge and begin feeding on violets. They grow and mature through six instar stages until late May when they pupate (Selby 2007). The life cycle of the regal fritillary is quite unique and is thought to be an adaptation to the phenology, or seasonal timing and nature of their larval food plant, the violet (Kopper et al. 2001). These small perennial violets produce abundant foliage in the spring for the growing larvae. However, in most areas they senesce in the heat of the summer and become unavailable to the larvae at that time. When this occurs, the regal fritillary is entering into its adult life and is no longer dependent on the violet. The fact that the violets remain unable to support larvae throughout the rest of the summer helps to explain the regal fritillary’s univoltine life cycle. It is through larval diapause coupled with the adult female reproductive diapuase that enables the larvae to maximize the benefits of fresh and abundant violet foliage when they are active in the spring (Kopper et al. 2001). 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Regal fritillary」の詳細全文を読む スポンサード リンク
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