Variant of Demodex folliculorum infesting the eyelids.

The mite Demodexfolliculorum, which is currently evoking interest amongst ophthalmologists throughout the world, has been thoroughly described in detail by Coston (i967), Smith and McCulloch (I969), and English (I969). Mites and ticks, in contradistinction to the other arachnids have fused segments, giving a characteristic morphological appearance. Accordingly, the adult type of Demodex folliculorum presents a vermiform or cigar-shaped profile (Fig. i) with a well differentiated prosoma incorporating head and thorax, and an opisthosoma consisting of abdomen and tail ending in a smoothly rounded off caudal extremity. The segmented thorax bears four paired appendages and the abdomen is distinguished by annular markings or grooves. This latter feature possibly is a type of dermatoglyphic adaptation to its follicular environment, allowing for its facility of ready ingress or egress.