Yucca Moth (Tegeticula yuccasella)

Description
yucca moth

Size

  • Is a small moth with a wingspan ranging from 18 to 28 millimetres (about one inch) across.
  • Females are slightly larger than males.

Appearance

  • Is white to whitish brown in colour.
  • Eyes are black and prominent against a white head.
  • Wings are slender.
Distribution
  • Yucca moths exist in sustainable numbers at only one of two naturally occurring soapweed (yucca) populations in southeastern Alberta.
  • The Lost River (Alberta) population is primarily distributed along a two-kilometre stretch of south-facing coulee slope along a tributary of the Milk River on land owned by the Lethbridge Agricultural Research Substation in Onefour, Alberta.
Natural History

Habitat

  • In Alberta, yucca moths are restricted to the Dry Mixed Grass Subregion. This semi-arid region has a continental climate with extremes of weather and large daily and seasonal variation in temperature.
  • This subregion has a typical continental climate that is characterized by low precipitation, hot summers and a high rate of evaporation.
  • At the northern edge of its range in Alberta and Montana, the yucca moth uses only soapweed for egg laying and larval feeding. This plant grows in sparsely distributed populations on well-drained, mostly south-facing coulee slopes.
  • The yucca moth has an obligate mutualistic relationship with the soapweed (yucca) plant, meaning that the moth and the plant require each other to survive and reproduce.
  • Because there is no other consistently successful mechanism of pollen transfer for the plants and because yucca moth larvae feed only on yucca seeds, neither species can survive without the other.

Food

  • Moths do not feed as adults and die after three to five days.
  • Upon hatching, larvae feed on developing seeds of the soapweed.
Reproduction and Growth

Breeding Behaviour

  • In Alberta, most adult moths emerge from the soil from the second week in June through to the second week in July. Shortly after emergence they gather and mate in freshly opened soapweed flowers.
  • Adult female yucca moths actively collect pollen from one soapweed plant then usually fly to another inflorescence. Upon finding a fresh flower, a female first inserts her ovipositor through the carpel wall and lays an egg next to the developing ovules.
  • She then climbs to the tip of the style, and using her maxillary tentacles (appendages unique to yucca moths), she actively transfers pollen into the stylar canal.

Growth Process

  • Moth eggs hatch after seven to ten days.
  • After approximately 50 to 60 days, the larvae chew their way out of the yucca fruit and drop to the ground via a silken thread.
  • Larvae burrow 5 to 20 centimetres (two to eight inches) into the soil, spin a cocoon of silk and sand particles and enter a dormant stage.
  • After a minimum dormancy of one year, larvae pupate and emerge from the soil as adults. Emergence usually coincides with yucca flowering.
Conservation and Management

Status

The yucca moth is not currently classified in the General Status of Alberta Wild Species report.

For more information on this species, see the Status of the Yucca Moth in Alberta report at:

Issues

  • The success of Alberta yucca moth populations is heavily dependant on the success of soapweed populations. Along with the recommendation to list yucca moth, soapweed has been listed as Endangered under the Wildlife Act.
  • Yucca moth distribution in Alberta is limited to locations where soapweed occurs, reproduces sexually and retains fruit.
  • Pronghorn eat individual soapweed flowers; whereas mule deer most often eat the entire flowering stalk. Complete or large reductions in soapweed fruit production can lead to complete reproductive failure of moths.
  • Soapweed plants have been destroyed by off-road traffic, affecting overall moth reproductive success.

 

Page Information

Updated: Jan 8, 2014