216 NOTES ON THE MOUTH-PARTS OF LICE. 



An examination of the distal end of the proboscis under a higher magnification (Fig. B., magnified 

 600 diameters) explains the reason, as the mouth parts exist, modified and, in part, reduced, about 

 the mouth opening. The latter is bounded dorsally by a curved plate [lb.), slightly bifid at its anterior 

 end, which bears two sensory bristles, with three pairs of strong chitinous denticles, increasing in size 

 from before backwards, which are set in articular areas, and are described by Piaget (1880. p. 658) 

 as movable. This plate appears to represent labrum plus clypeus, the boundary between the two not 

 being demarcated. Laterally the mouth is bounded by two heavy chitinous pieces, showing two series 

 of hooks, a dorsal and a ventral, curving outwards and slightly backwards, the piece of either side being 

 movably hinged. It is not possible to state with certainty what these appendages represent, but they 

 may be fused maxilla and mandible, an interpretation suggested by the double series of hooks ; or may 

 consist of mandible or maxilla alone. The ventral boundary is formed by a curved plate (la) deeply 

 bifid in the middle, each lobe tearing a rudimentary palp (/./>.) exactly like those of Mallophaga. This 

 plate is represented in the figure as projecting beyond the labrum, but, in reality, it is conterminous 

 anteriorly with the latter, projecting a little beyond it laterally. There can be no doubt that this plate 

 represents the labium. It bears upon its ventral surface strong paired denticles which are not indicated 

 in the figure. 



Haematomyzus, consequently raises some interesting questions in connection with the mouth- 

 parts of lice. First we may ask whether it be a louse at all. I can see no reason for doubt upon this 

 point. Piaget, its discoverer, had none. Enderlein, who has devoted a great deal of attention to the 

 systematica of lice, has expressed no doubt, and he is responsible for creating the family Haematomy- 

 zidae to contain it. Fahrenholz, another modern worker on the Siphunculata, who has assuredly 

 examined the form, as he has described a variety (1910, p. 67), has not raised the point of its erroneous 

 inclusion. 



Haematomyzus would seem, therefore, to be a louse. Why, then, does it differ so remarkably, as 

 regards its mouth-parts, from other Siphunculata ? Haematomyzus pierces with the whole of its 

 probosus. which is simply the anterior part of the head drawn out into a long tube, bearing terminal 

 mouth-parts ; while in other lice the piercing is done by slender stylets protruded from a pocket beneath 

 the pharynx. It seems to me that Haematomyzus is a primitive form, as I should expect from its host, 

 derived from an ancestral louse group which must have had a palpigerous labium and other fairly 

 typical mouth-parts. If it be claimed that it is not primitive, but highly adapted to a special host 

 habitat, then it certainly cannot have been modified from any group of insects with hemipterous mouth- 

 parts, for it is impossible to conceive a reversion from the highly specialised condition of the bugs to 

 that of a palp-bearing labium of a type so characteristic in Mallophaga. 



Specialised and modified as it may be, Haematomyzus seems to me to afford further justification 

 for my reuniting the Siphunculata and Mallophaga wdthin a single order. Anoplura (1916a, p. 25) ; 

 and to constitute a fatal stumbling-block to the idea of Hemipterous homologies. 



References. 

 Cummings (1913), Bull. Ent. Research, iv., pp. 35-45. 

 Enderlein (1904), Zool. Anzeiger, xxviii., pp. 121-147. 



(1905), Zool. Anzeiger, xxviii., pp. 626-638. 



Fahrenholz (1910), J ahresbericht d. N eider sacks. Zool. IV 1 . Hannover, pp. 57-75. 

 Harrison (1916), 7'in<. Camb. Phil. Soc, xviii., pp. 207-2_><>. 



(1916a), Parasitology, ix., pp. 1-156. 



Kellogg & Xakayama (1914). I'ut. News, xxv., pp. 193-201. 

 Piaget (1880). Les Pideculines, Essai Monographique, Leyden. 



