Cucumber moth

Appearance

The wingspan is about 30 mm. Adults have translucent whitish wings with broad dark brown borders. The body is whitish below, and brown on top of head and thorax as well as the end of the abdomen. There is a tuft of light brown "hairs" on the tip of the abdomen, vestigial in the male but well-developed in the female. It is formed by long scales which are carried in a pocket on each side of the 7th abdominal segment, from where they can be everted to form the tufts. Unfertilized females are often seen sitting around with the tuft fully spread, forming two flower-like clumps of scales, which move slowly to spread their pheromones. These have been identified as consisting mainly of -10,12-hexadecadienal and -11-hexadecenal.

From its closest relatives, the cucumber moth is most reliably distinguished by microscopic examination of the genitals. In the male, the clasper's harpe is twice as long as it is wide, with costa and sacculus running almost in parallel and being strongly sclerotized, and a rounded cucullus. From the center of the harpe, which is otherwise only weakly sclerotized, a thin spine extends. The uncus is covered in bristles and ends in a small tube; it is a bit longer than the tegumen which in turn is about as wide as it is long. The vinculum is almost quadratic, and the anellus forms a small triangular plate which is more strongly sclerotized. The aedeagus is almost straight, strongly sclerotized below, and has a flattened curved process at end.

In the female genitals, the ostium is transverse and oval, and the antrum broadly sclerotized. The ductus seminalis insert from above, a bit before the forward edge of the antrum. The bursa copulatrix is long and slim, with the forward third particularly narrow; its wall is covered with many short spines, and the hind end almost seamlessly merges into a short and barely distinguishable ductus bursae.

Distribution

The natural range of this moth seems to extend from South Asia to southern China and Taiwan, and south through Southeast Asia top the Maluku Islands of Indonesia; it does not seem to extend to the Philippines, but is widespread in Australia and is a pest of cucurbits in the northern part of the continent. It is possible that it was introduced by trade and transport of its host plants to oceanic islands, such as Fiji, Ponape in the Caroline Islands and the Marquesas Islands in different regions of the Pacific, and Mauritius in the western Indian Ocean. It has been reported from some localities in Africa, but there it is probably introduced too.

As implied by the common names, the caterpillar larvae of this moth are a frequent agricultural pests. It is perhaps most noticeable as a pest of cucumbers, but this seems more due to the widespread production of these than to the moth's preferences; ''D. indica'' is quite polyphagous and prefers other Cucurbitoideae to cucumbers. Typically, the leaves of the foodplants are eaten.

Host plants are usually eurosids and include:
⤷  Cucurbitaceae
⤷ * Benincaseae: Calabash , Angled Luffa , Egyptian Luffa , probably others
⤷ * Cucurbiteae: pumpkins
⤷ * Melothrieae: cucumber and others
⤷ * Trichosantheae: Snake Gourd , ''Trichosanthes tricuspidata''
⤷  Other families:
⤷ * ''Erythrina corallodendron''
⤷ * Levant cotton

Habitat

The natural range of this moth seems to extend from South Asia to southern China and Taiwan, and south through Southeast Asia top the Maluku Islands of Indonesia; it does not seem to extend to the Philippines, but is widespread in Australia and is a pest of cucurbits in the northern part of the continent. It is possible that it was introduced by trade and transport of its host plants to oceanic islands, such as Fiji, Ponape in the Caroline Islands and the Marquesas Islands in different regions of the Pacific, and Mauritius in the western Indian Ocean. It has been reported from some localities in Africa, but there it is probably introduced too.

As implied by the common names, the caterpillar larvae of this moth are a frequent agricultural pests. It is perhaps most noticeable as a pest of cucumbers, but this seems more due to the widespread production of these than to the moth's preferences; ''D. indica'' is quite polyphagous and prefers other Cucurbitoideae to cucumbers. Typically, the leaves of the foodplants are eaten.

Host plants are usually eurosids and include:
⤷  Cucurbitaceae
⤷ * Benincaseae: Calabash , Angled Luffa , Egyptian Luffa , probably others
⤷ * Cucurbiteae: pumpkins
⤷ * Melothrieae: cucumber and others
⤷ * Trichosantheae: Snake Gourd , ''Trichosanthes tricuspidata''
⤷  Other families:
⤷ * ''Erythrina corallodendron''
⤷ * Levant cotton