Large dragonflies and hornets catch honey bees on the wing and feed on them, and many other bee predators are insects. The major insect pathogens and parasites are described below in some detail.
Varroa destructor mites were introduced in the United States in 1987 from the Asian hive bee Apis cerana, and they spread across the country in five years, living up to their name by killing many American honey bees. They are eight-legged external parasites that can only reproduce in a honey bee colony, although they are sometimes found on other flower-feeding insects. Varroa mites feed on the hemolymph of bees in the larval and pupal stages. They are called ectoparasites because they stay on the outside of the bees as they feed, creating open wounds which make the weakened bees vulnerable to pathogens.
Certain viruses can cause the pupal bees to develop deformities that include the possible absence of a leg, crumpled or vestigial wings, a shortened abdomen, or an overall reduction in size. If infested bees survive and are able to fly, their ability to forage normally does not seem to be impaired, but there may be non-lethal behavioral impacts about which we know very little. There are some chemicals that dissuade mite populations, but some mites have become immune to these drugs.
Tracheal mites, Acarapis woodi, are small, spider-like endoparasites that infest the breathing tubes, or trachea, of honey bees, feeding on a bee's hemolymph from inside the bee's body. Dense infestations of tracheal mites can result in colony death during the winter months because, with many mites in the trachea, the bees cannot breathe normally and aren't able to regulate the colony's temperature. Jon Harrison and his colleagues at Arizona State University studied the impact of mite infestation on the breathing of bees.
These mites are normally found on an Asian cousin of the European honey bee, and they were first identified in Mexico in 1980 and then found in Texas in 1984 and in southern Arizona in 1988. While it is unpleasant to think about it this way, tracheal mites exist like lice on people - the infection is present in low numbers, and they do not do much permanent damage to people suffering with them. Why tracheal mites jumped onto a new species is not understood, and, unfortunately, there is no clear treatment to prevent them except for keeping colonies strong and healthy.
There are two moth species that feed on the materials inside a beehive - both are generally called wax moths, but they are different creatures: the greater wax moth, Galleria mellonella, and the lesser wax moth, Achroia grisella. As adults, they are small, grayish-brown, and nocturnal, and they both have a keen ability to detect beeswax, in which they lay hundreds of tiny eggs. Wax moth larvae eat the larval skins that are shed when the adult bees emerge, and they also eat impurities in the wax of the bee brood combs, such as pollen and all sorts of debris carried on the thousands of bee feet that have walked across it. If a bee colony is healthy and strong, meaning it has a full complement of workers, the bees can detect and remove the moth larvae before too much damage is done to the colony, but as the larvae grow, they burrow into the wax and can render the combs inhospitable to bees.
These whitish-gray larvae are certainly not a pleasant sight in a beehive, leaving trails of silk behind them as they move and dig into the wax. Freezing the wax honey frames after the honey has been extracted can kill wax moths eggs and larvae. Wax moths also do not like the fumes of various chemicals, such as paradichlorobenzene (PBD), which is an appropriate (and legal) preventative treatment against these pests and does not hurt the bees. PBD cannot be used in colonies that are actively storing honey because this fumigant is not safe for human exposure or consumption.
A bee louse is actually a tiny wingless fly, Braula coeca, which lives inside bee colonies. They cling to a honey bee and take food directly from its mouth. If a hive is infested with them, several adult flies may live on a queen, but usually only one will be found on a worker. Bee lice do little damage to bee colonies, and so they are not thought of as parasites, but rather as commensal animals with bees - meaning their presence is usually tolerated by the bees. Because bee lice are killed by medications given to remove Varroa mites from bee colonies, they are rarely seen inside beehives. Elizabeth Evans has been keeping bees for nearly twenty years and has never seen one.
Small hive beetles, Aethina tumida, are the newest pest in North American beehives. First discovered in the United States in Florida in 1998, the honey-eating beetles were somehow imported from African subspecies of honey bees, where they seem to live quietly in beehives. In the European subspecies of bees that are common in the United States, small hive beetle infestations can cause serious damage to the stored honeycombs and to the honey crop. The beetle grubs (larvae) burrow through and damage the honeycombs, which results in honey running out of the combs and fermenting or becoming frothy. The larvae defecate in the honey and it becomes discolored, and because they can live in honeycombs that have been removed from beehives, they can ruin comb honey that is waiting to be extracted. It is unclear why the small hive beetle can coexist in African beehives as a minor pest but can become a serious threat in North American hives.
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