Percentages (mean ± SE) for the different categories of damages to <i>Varroa destructor</i> recorded in the colony debris of <i>A</i>. <i>m</i>. <i>scutellata</i> and <i>A</i>. <i>mellifera</i> hybrids of European origin in Kenya and USA respectively.

<p>Percentages (mean ± SE) for the different categories of damages to <i>Varroa destructor</i> recorded in the colony debris of <i>A</i>. <i>m</i>. <i>scutellata</i> and <i>A</i>. <i>mellifera</i> hybrids of European origin in Kenya and USA respectively.</p

Mean ± standard error of mite infestation rates, daily mite fall and percentage of damaged mites on adult honeybee workers in colonies of <i>A</i>. <i>m</i>. <i>scutellata</i> and <i>A</i>. <i>mellifera</i> hybrids of European origin.

<p>Mean ± standard error of mite infestation rates, daily mite fall and percentage of damaged mites on adult honeybee workers in colonies of <i>A</i>. <i>m</i>. <i>scutellata</i> and <i>A</i>. <i>mellifera</i> hybrids of European origin.</p

Photographs showing the different damage patterns in mature female <i>Varroa destructor</i> mite (×40 Magnification).

<p>(A and D) Damaged categories from literature [<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0179329#pone.0179329.ref036" target="_blank">36</a>–<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0179329#pone.0179329.ref038" target="_blank">38</a>]. (B and C) Additional damage categories reported in this study. (E-J) Previously known classification of damage to the mites reported by Corrêa-Marques <i>et al</i>., [<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0179329#pone.0179329.ref017" target="_blank">17</a>].</p

Hygienic and grooming behaviors in African and European honeybees—New damage categories in <i>Varroa destructor</i>

<div><p><i>Varroa destructor</i> is an ectoparasitic pest of honeybees, and a threat to the survival of the apiculture industry. Several studies have shown that unlike European honeybees, African honeybee populations appear to be minimally affected when attacked by this mite. However, little is known about the underlying drivers contributing to survival of African honeybee populations against the mite. We hypothesized that resistant behavioral defenses are responsible for the survival of African honeybees against the ectoparasite. We tested this hypothesis by comparing grooming and hygienic behaviors in the African savannah honeybee <i>Apis mellifera scutellata</i> in Kenya and <i>A</i>. <i>mellifera</i> hybrids of European origin in Florida, USA against the mite. Grooming behavior was assessed by determining adult mite infestation levels, daily mite fall per colony and percentage mite damage (as an indicator of adult grooming rate), while hygienic behavior was assessed by determining the brood removal rate after freeze killing a section of the brood. Our results identified two additional undescribed damaged mite categories along with the six previously known damage categories associated with the grooming behavior of both honeybee subspecies. Adult mite infestation level was approximately three-fold higher in <i>A</i>. <i>mellifera</i> hybrids of European origin than in <i>A</i>. <i>m</i>. <i>scutellata</i>, however, brood removal rate, adult grooming rate and daily natural mite fall were similar in both honeybee subspecies. Unlike <i>A</i>. <i>mellifera</i> hybrids of European origin, adult grooming rate and brood removal rate did not correlate with mite infestation levels on adult worker honeybee of <i>A</i>. <i>m</i>. <i>scutellata</i> though they were more aggressive towards the mites than their European counterparts. Our results provide valuable insights into the tolerance mechanisms that contribute to the survival of <i>A</i>. <i>m</i>. <i>scutellata</i> against the mite.</p></div

Correlation between daily natural mite fall, total natural mite fall, percentage damaged mites, different categories of damage to the mites and <i>Varroa</i>-mite infestation level per colony in honeybees of African and European origin in Kenya and USA respectively.

<p>Correlation between daily natural mite fall, total natural mite fall, percentage damaged mites, different categories of damage to the mites and <i>Varroa</i>-mite infestation level per colony in honeybees of African and European origin in Kenya and USA respectively.</p