VII] 



EXTERNAL ANATOMY 



55 



probable that this organ is responsible for some of the charac- 

 teristic buzzing of the mosquito. 



Each halter consists of a short chitinous rod arising from 

 a basal plate and ending in a rounded knob. The concave 

 basal plate and a knob at the base of the halter are covered 

 with small papillae, and Shipley and Wilson have suggested 

 that by these two surfaces rubbing against each other when 

 the halter vibrates, a faint note may be produced. 



scl 



Fig. 28. View of under surface of the base of the wing of Anopheles maculi- 

 pennis, shewing stridulating organ. After Shipley and Wilson. 



A, right half of thorax with right wing. The shaded portion indicates 

 the area which bears the stridulating organ. B, the stridulating organ, 

 highly magnified, bl, ridged blade ; h, haltere ; kn, knob ; scl, sclerites ; 

 tb, toothed bar. 



The abdomen consists of eight segments, each composed of 

 a dorsal chitinous plate, the tergum, and a ventral chitinous 

 plate, the sternum, between which is a soft membrane, the 

 pleuron. On each side are six abdominal stigmata opening 

 in segments two to seven inclusive. The surface of the abdo- 

 men may be covered either with scales or hairs. The terminal 

 segment is bilobed and in the male each lobe terminates in a 

 long chitinous claw, the clasper. 



