166 grosse's classification and 



Respiratory apparatus. — There are seven pairs of stigmas : one 

 in the prothorax and six abdominal. Each stigma has internally 

 a crown of fine hairs to protect from impurities. A pair of strong 

 longitudinal tracheae send branches to the stigmata and are united 

 to each other by a strong cross branch in the abdomen, and 

 smaller ones in the head and thorax. 



Dorsal vessel. — Grosse could not succeed in making a prepara- 

 tion of this, but in the recently-moulted living animal it can be seen 

 pulsating through the back. 



Nervous system. — This consists (in PniLOPTERiDiE) of two 

 cephalic ganglia and three thoracic ganglia. The preoesophageal 

 ganglion is much larger than the suboesophageal, and they are 

 united by strong commisures. The last thoracal ganglion is large, 

 and sends back nerves to supply the abdomen. 



Antennce. — In LiOTHEiDiE these are four-segmented, club-shaped 

 or knobbed, the terminal segment spherical, lying in a hollow of 

 the sub-terminal one (Fig. i, at). In a cross-section of the termi- 

 nal segment of LcE??wbothrium are seen round nucleated cells, 

 apparently ganglionic enlargement of nerves. The Liotheidae 

 have the antennae alike in both sexes, but in Philopterid^ the 

 third segment of the antennae of the male has a lateral process, 

 sometimes so large as to make the antenna resemble a lobster's 

 claw. Nitsch states that it is for holding the female. 



Eyes. — These lie on the margin of the under surface of the 

 head behind the antennae. Authors have hitherto ascribed a 

 single pair of eyes to all Mallophaga. But in all Philopterid 

 genera examined {Goniodes, Docophorus, Lipeurus, Nirmus) the 

 author found a single pair, and in all Liotheid genera {Tetroph- 

 thal??ius, LcBmobothritmt, Menopofi, Trinotum, and Colpocephalwii) 

 he found two pairs of stemmata. If this character holds good for 

 the remaining genera, it will still further separate the two chief 

 divisions of the Mallophaga. 



The eyes of Mallophaga are simple, provided with a lens- 

 shaped thickening of the cuticle. In young specimens the eye 

 has no pigment, but in older specimens it has pigmented retinal 

 cells. The eye of LcEmobothriu7?i, examined by means of sections, 

 has, under the chitin-thickening (Fig. lo, /.), twenty-four pig- 

 mented retinal cells (r.), clavate and nucleated with nucleoli. 



