Tegeticula intermedia

Yucca flaccida (as Yucca orchioides var. major) Bot. Mag. 103. tab. 6316. 1877

Larvae feed on a variety of plants within the yucca genus, depending on the region of the population. Some host species include Yucca filamentosa, Y. arkansana, and Y. flaccida.[1]

Larvae feed on yucca seeds within the fruit. Since there is an abundance of seeds within the fruit, the larva does not impinge too heavily upon the health of the yucca plant or compete too strongly with other pollinator species of yucca moths.[7] These seeds are the only known food source to the yucca moth larvae. The larvae of T. intermedia superficially crawl towards the ovary so they can burrow past the wall and commence feeding upon the developing seeds. They then escape from the flower, falling to the ground to burrow and cocoon.[8]

Adults have such short lifespans that they do not need to eat to achieve their reproductive goals. Although they do have mouth parts or tentacles, these are used for collecting pollen than for feeding.[7]

The host yucca plant regulates the number of eggs laid by selectively abscessing flowers that are overburdened with eggs. The plant selects which flowers to abscess by assessing its weight due to the excess of eggs and by recognizing severe ovule damage due to excessive oviposition. In T. intermedia, the moth avoids ovipositing into the ovule directly. Thus, the plant does not perceive ovule damage, and will not abort the flower.[4]

Although most yucca moths deposit their eggs in the ovule of the flower, Tegeticula employs different methods of laying eggs. T. intermedia employs superficial oviposition, meaning that the yucca moth lays its eggs very slightly beneath the plant tissue, so as not to damage the yucca ovule. This strategy allows the moth to bypass the yucca plant's regulation of the number of eggs it hosts, leading to exploitation of the plant.[4] Oviposition takes place in the fruit of the yucca.[8]

Yucca moths mate in the spring when the yucca flowers are in bloom. They then mate on the yucca flower, usually in the evening when the flower will be open. Then, the female moth will lay eggs in the wall of the fruit of the yucca, typically around 6-20 day old fruits.[8] T. intermedia is unique in that it will superficially oviposit eggs one at a time so as to deceive the yucca plant.

Once laid, the larvae will hatch quickly in only a few days time. During early instars the larvae feed inside the fruit on the developing seeds. Later in their development, the matured instars leave the fruit, preferably after a rain storm or during wet conditions to make escape easier.

The larvae fall to the ground, burying themselves in a cocoon one to two dozen centimeters below ground during pupation.

The adult moths will emerge in the following spring to restart the life cycle.[9][7]

Female yucca moths use their antennae to sense if a flower has already been visited, and presumably oviposited on, by another female by detecting trace pheromones left behind. If detected, the female leaves and finds another flower that hopefully has not been pollinated yet.[2][3]

Yucca moths get their name for the intense, obligate mutualism they share with the yucca genus that has evolved over millions of years. The yucca moth is the only insect capable of pollinating the yucca plant. Likewise, the yucca plant is the only biological resource that sustains the moth. Both are so deeply interdependent on each other for survival that in most cases one local population extinction event of either the plant or moth would lead to an extinction of the complementary species.[6]

However, Tegeticula intermedia is a cheater species of yucca moth that parasitizes the yucca plant. It has evolved to superficially oviposit to avoid detection by the yucca that would allow it to lay many eggs without inducing flower abortion. The key trait of this species is that it lays eggs without pollinating the yucca. It enjoys the benefits of reproducing without the costs of aiding yucca reproduction at the expense of the host.[8]