A morphological study of the probosces and observations on the feeding habits of fruit-piercing moths

Abstract

A description is given of how fruit-feeding noctuids pierce fruit and feed on it. The functions and importance of the following feeding movements are discussed: probing with the proboscis, oscillation of the head, to and fro sliding of the galeae an4 the vibration of the proboscis! Two proboscis cleaning processes, using saliva and a labial brush, are described

Moths feeding on fruit in orchards were recorded as either feeding on "rotten fruit", "damaged fruit or on "sound fruit". Later experiments with caged moths and morphological studies of their proboscis, showed that the moths recorded under the category "sound fruit" are the so-called piercers while those in the other two categories are the non-piercers. Piercers actually preferred to feed on undamaged fruit.

Hourly counts of fruit-feeding noctuids throughout four nights during two seasons revealed that greatest moth activity occurred during the first three hours after dark, followed by a small decrease in numbers around midnight. The numbers increased again at about 01h00 and this number was maintained until 04h00.

To determine whether fruit-feeding noctuids return to the same source of food on subsequent nights, moths were caught on the only peach tree that still bore fruit in an orchard in February. On two evenings the following numbers of moths were caught, marked and released: 4 Achaea catella, 84 A. finita, 65 A sordida and 13 Sphingomorpha chlorea. The highest percentage return (7,6%) occurred one day after marking. The longest time lapse between marking and subsequent recording was four days (a single specimen).

Tests with caged fruit-feeding moths revealed that there was a clear distinction between moths being able to pierce _the skin of fruit (piercers) as opposed to those that were unable to pierce the skin of even soft ripe fruit (no piercers). For, non-piercers the barriers that prevent them: from feeding on fruit are firstly, the intact skin of the fruit and secondly, the hardness of exposed fruit flesh.

A general description of the proboscis of fruit-feeding noctuids is given, followed by a description of the proboscis of individual species. The apical regions of the galeae of nine fruit-feeding moths are figured, namely Achaea finita, dianaris, Calpe provocans, Cyligramma latona, Othreis materna, Parallelia algira, Pericyma atrifusca, Serrodes partita and Sphingomorpha chlorea.

Three morphological differences between the proboscis of piercing and non-piercing noctuids exist: 1. the presence of galeal barbs in piercers; 2. the non-tapering proboscis with a wedge-shaped tip of piercers as compared to the gradually tapering proboscis of non-piercers; 3. the very heavily sclerotized and sharply pointed galeal apices of piercers as against the non-piercers' slightly pointed to blunt galeal apices with sclerotization absent or limited to the extreme tip.