574 MEDICAL ENTOMOLOGY 



arrangement in different specimens and are apt to fade when the tick 

 is kept in alcohol. 



Situated at the lateral margins of the scutum, either on the edge 

 or just inside it, there are two small globular protuberances, the 

 eyes (Plate LXXII, figs. 1 and 2) ; they maybe of a 

 light yellowish colour or dark brown. In some species 

 they are more or less flattened and inconspicuous, while in others they 

 appear as buttons sunk into small pits. Eyes are present in certain 

 genera and absent in others ; as they can be readily seen with a good 

 hand lens their shape, size and position are of some taxonomic importance. 



About the centre of the scutum of the male, and just posterior to it in 

 the female, there are two spots, the dorsal porose areas or foveae. When 



examined with a high power they are seen to consist 

 Dorsal porose areas 



01 a number of small protuberances, each of which has 



a pore at its summit ; they occur in both sexes when present in the 

 species, and have been described from several genera (Dermacentor, 

 Rhipicephahis, Margaropus and Hyalomma). Their function is unknown, 

 but they are probably sense organs. 



Cervical groove (figs. 1, 2 and 6) is the name applied to the furrows 

 which extend backwards from the inner angles of the scapulae towards 



the posterior margin in both sexes. The lateral groove 

 Grooves and furrows, l . m , , ,, ., , . ... 



Plate LXXII ' * ' extends along the side of the scutum in both 



sexes ; in the male it often reaches the posterior 

 margin. The marginal groove runs along the side of the body of the 

 female. Median and postero-lateral furrows (fig. 6) are the names given 

 to certain ill-defined depressions near the posterior borders in the males 

 and females of certain species ; they are not, however, of much import- 

 ance, as they alter in shape when the tick is replete with blood and during 

 muscular contraction. The marginal or postero-marginal festoons (figs. 

 1, 2 and 6) are usually eleven in number, and are best seen in the 

 males and unfed females. They are small chitinous plates bounded by 

 furrows, and give the posterior margin of the body of the tick a festooned 

 appearance. 



On the ventral surface of the body the following structures should 

 be noted : Genital aperture, ventral shields, anal aperture, ventral and 



anal plates, stigmata or spiracles, legs, furrows, grooves 



and pits. The genital aperture (Plate LXXII, fig. 3) 

 ure and grooves ^ es m ^ e median line towards the anterior end and just 



behind the basis capituli ; it will be readily recognized 

 as a transverse slit, guarded anteriorly by a chitinous flap, the apron, 



