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Lilypad Forktail



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Ischnura kellicotti

Williamson, 1898


Order Odonata
Suborder Zygoptera
Superfamily Coenagrionoidea
Family Coenagrionidae
Genus Ischnura
Species kellicotti Williamson, 1898 [Ischnura]


Identification

In males the postocular spots are unusually large and the pterothorax is bright blue with a broad black middorsal stripe and pair of black humeral stripes. The abdomen is largely black with blue on parts of segments 1-2 and 7-10. The forewing pterostigma is larger than its tan hindwing counterpart and becomes bright blue anteriorly with maturity. Males also lack a notable dorsoapical projection on segment 10. The cerci are distinctive, sloping ventrolaterally to form an acute apex. The paraprocts each have a lower appendage that projects posteroventrally. Females exist in both a blue and red-orange form. Each is patterned like the male, with pale colors replaced by red-orange in the latter. A small vulvar spine is usually visible on segment 8.

Size

Total length: 25-31 mm; abdomen: 19-24 mm; hindwing: 12-18 mm.

Similar Species

The bright blue or orange color of this species may result in its initial confusion with bluets like Skimming Bluet (Enallagma gemnatum). In Lilypad Forktail, however, the dorsum of abdominal segment 2 is largely blue and the pale postocular spots are much larger than in Skimming Bluet. No other forktails in our region have the large postocular spots seen in this species.

Habitat

Strongly associated with floating lily pads in lakes.

Discussion

This species is unique, among Nearctic odonates, in its obligatory relationship with water lilies (Nuphar and Nymphaea ) in both the larval and adult stages. Williamson (1899a ) was the first to report this little studied relationship. He stated that he, "...never saw one at rest on any other location than a flat-floating leaf of the white water-lily. They were quarrelsome neighbors and frequently attacked [Skimming and Orange (E. signatum ) Bluet], though apparently without serious injury." Larvae cling to the bottom of the lily pads and emerge by crawling on top. The adults are nearly always encountered perching or ovipositing on these plants. They somtimes will exhibit a unique posture; while perching on a pad with the abdomen curled downward, they will tilt back on the abdomen with the front legs in the air ready for an immediate getaway. Females, unaccompanied by males, take up to 20 minutes to deposit eggs. One study on the color morphs in a north-central Texas population of this species found no evidence for dichromatic females, but rather that the color change was ontogenetic. Young teneral females are orange, but with the onset of reproductive maturity become blue. The authors of the study found females of netted copulating pairs were nearly always of an intermediate color form. The young orange color form, however, may be reproductively mature, as indicated by a photograph of a copulating pair in Westfall and May (1996). Interestingly, the same study found that although Lilypad Forktail is rarely harassed, females do not utilize an active mating refusal display to thwart off nearby males, potentially explaining the photograph.

Distribution

Eastern U.S. from Florida to Maine west to Michigan and south to Texas.