| Dogbane Tiger-moth | |
|---|---|
| Scientific classification | |
| Kingdom: | Animalia |
| Phylum: | Arthropoda |
| Class: | Insecta |
| Order: | Lepidoptera |
| Family: | Arctiidae |
| Genus: | Cycnia |
| Species: | C. tenera |
| Binomial name | |
| Cycnia tenera Hubner, 1818 |
|
Cycnia tenera, the Dogbane tiger-moth or Delicate Cycnia is a moth in the family Arctiidae. It occurs throughout North America, from southern British Columbia to Nova Scotia southwards to Arizona and Florida. Range map: [1].
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It is a common feeder on Apocynum cannabinum (dogbane, Indian hemp) which produces a milky latex containing cardenolides, toxic cardiac glycoside that defend against herbivores (Cohen and Brower, 1983). It also feeds on milkweed species, Asclepias, at least in parts of its range, but is most commonly reported from dogbane. Its interactions with bats have been much studied, but are an area of dispute regarding whether the clicks emitted by adult moths are disruptive of bat echolocation, or merely aposematic warning signals. The two functions are not mutually exclusive, however, so that it may not be possible to resolve the issue.
This moth has several generations per year through much of its range, so that caterpillars may be found from June to November (Wagner 2005).
Eggs are laid in clutches of 50-100. Larvae are reported to feed in aggregations of 5 to 7, at least in the early instars (Cohen and Brower, 1983). Caterpillars are covered all over in soft grey to whitish hairs. Larvae feed at night.
The cocoon is grayish and covered in hairs from the caterpillar's body.
Wings are white with a buttery yellow margin along the front of the forewing, legs are black. The underside of the forewing may have a dusting of black. The body is yellow with a row of black spots. Wingspan 30-40 mm.
Bats refuse to eat either muted or intact moths of C. tenera (Ratcliffe and Fullard, 2005). Hawking bats, that is, those seeking moths in flight, attacked intact, clicking C. tenera less frequently than surgically muted (with tymbal organs destroyed) moths in experiments. Intact moths emitted calls when the hunting bats switched from search phase calls to approach phase calls (Fullard et al., 1994). In gleaning attacks, when bats attack moths perched on surfaces, bats use a different frequency of sound that these moths cannot hear (Fullard 1979), and the moths do not respond until actually handled by bats. Then clicking moths were dropped more frequently than mute moths.
In a set of experiments using bats that had never been exposed to moths before, Hristov and Conner (2005) found that the clicking signals helped the bats to learn which moths are distasteful, and so to avoid them. They did not rule out a jamming function for the calls, however, and Ratcliffe and Fullard noted that 20% of these native bats aborted attacks on the moth.
The calls are additionally used by male moths to signal to female moths (Conner 1987). Like many Arctiinae C. tenera flies all day and night, though preferentially some time after dusk. Nonetheless it is certainly not a well-loved prey item of diurnal predators such as insectivorous birds either. Its sense of hearing, on the other hand, is only moderately well-developed. Thus, the calls of the Delicate Cycnia have more of a defensive than a social function, and the aposematic role is likely to be significant.(Fullard & Napoleone 2001).