Stylet penetration by Bemisia argentifolii (Homoptera : Aleyrodidae) into host leaf tissue

Silverleaf whitefly, Bemisia argentifolii Bellows & Perring, adults and nym phs feed on the phloem tissue of host plant leaves. Infested leaves were ra pidly fixed to prevent the insects from withdrawing their mouthparts. The a dult stylet bundle enters the labial groove of the labium between the first and second segments and is completely contained within the labium except d uring feeding. Stylet length is equal to the combined length of labial segm ents 2, 3, and 4. Stylet penetration can be determined by examining the pos ition that the stylet enters the labial groove. The physical force necessar y for adult stylet penetration is derived from changes in the position of t he whitefly head during feeding. The head is bent over the labium, which is attached to the leaf surface, forcing the stylet bundle down the labial gr oove and into the host tissue. Nymphal stylet lengths were found to be long er than previously reported, and of sufficient length to reach the phloem t issue in cotton and hibiscus leaves from essentially any position on the ab axial leaf surface.