Behavior And Ecology

Only a few groups of moths have become adapted for feeding directly on secretions and body fluids of live animals. This behavior apparently is derived from the commonly observed habit of adult lepidopterans feeding on animal excretory products such as fecal material, urine-contaminated substrates, and animal secretions such as saliva and nasal mucus smeared on vegetation or other objects. Imbibing fluids from the wounds and eyes of host animals is a behavioral modification requiring relatively minor morphological changes. In those species that feed on eye secretions, the proboscis is frequently moved over the sensitive eye region to irritate the conjunctiva and increase the flow of tears, on which the moths feed. At least one genus (Calyptra) includes species that have the ability to actually pierce the skin to feed directly on blood. It has developed unique modifications of the proboscis, notably hooks and erectile barbs (Fig. 18.2C). They are movable by internal hemolymph pressure which, aided by special proboscis motions, enables the proboscis to penetrate vertebrate tissues.

Moths which are attracted to animals are called zoophilous. They have been observed feeding on the following animal fluids: lachrymal secretions from eyes, blood and skin exudates associated with wounds, nasal secretions, saliva, perspiration, urine, and droplets of blood extruded from the anus of mosquitoes feeding on host animals. Because lepidopteran adults, with few exceptions, lack proteinases and therefore cannot digest proteins from these fluids, this specialized feeding behavior is believed to serve primarily as a means of obtaining salts. The feeding time for most zoophilous species is usually a few minutes.

Species which feed about the eyes on tears from the lachrymal glands are called lachrypbagous. They also are called tear drinkers and eye-frequenting moths. Lachryphagy is the most striking zoophilous behavior, as documented by Banziger in Southeast Asia. Since the first observation in 1904 of a moth feeding on the eyes of a horse in Paraguay (Shannon, 1928), lachryphagous moths have been reported attacking a wide range of wild and domestic animals, particularly ungulates and elephants. Zebu and water buffalo tend to be particularly favored hosts; other common hosts include horses, mules, tapirs, rhinoceroses, kangaroos, deer, and humans. It appears that many species exhibit a fairly high degree of host specificity at the order level.

Most lachryphagous species settle on the host to feed; others tend to hover or continually flutter their wings, remaining partially airborne while feeding. The proboscis is used to feed on tears flowing from the eyes. In some cases, it is used to irritate the conjunctiva or cornea and to feed directly on the eye tissue itself. Many lachryphagous moths are capable of slipping the proboscis between the closed eyelids of sleeping or dozing animals. Some even continue to feed when the host animal tightly closes the eyelids or blinks as a defensive response to the associated irritation. Other moths may irritate eye tissues, particularly the sensitive inner surface of the lids, with their tarsal claws while they attempt to feed.

Some adult moths are attracted to open wounds, where they imbibe blood and other host fluids. In most cases the feeding behavior is similar to drinking water and other fluids from the surface of mud, fresh animal manure, or honeydew. In other cases the moths actually probe the wound, penetrating damaged tissues to feed on fresh blood. They are variously called wound-feeding, hematophagous, and blood-sucking moths. Only a few taxa of skin-piercing moths are capable of piercing intact skin in order to feed.

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