ON MACKAYIA DIMORPHA 253 



At their posterior limit each bears a heavy spine like those 

 near the apex of the signature. The square formed by the 

 four spines is a conspicuous feature of the mid-region of the 

 head. There is a dark, clearly limited spot before the eye, 

 but inwards the ocular band is ill-defined. Occipital bands 

 somewhat widely apart at base, where there is an intensely 

 dark spot on each. These bands slant up to the oculars, 

 which they do not quite reach, becoming indistinct in that 

 neighbourhood. Before they become indistinct the occipital 

 bands send off a short faint branch on the inner side. 

 Antennae : first joint, which bears one long hair on its 

 upper surface, deeply inset in the head, long, though not 

 equal to the other joints together ; third joint transverse, 

 with triangular appendage. Trabecular long, reaching to 

 beyond the middle of the first joint. Eyes prominent, 

 with one very short bristle. Across the posterior region 

 of the head runs a row of four hairs, and there are two 

 additional hairs near the occipital edge. Behind the eye the 

 temples bear two spines followed by two very long hairs. 

 Occipital edge nearly straight, with two short hairs on" each 

 side, placed outside the occiput proper. On the ventral 

 surface of the head, at about the level of the clypea] suture, 

 is an entire transverse membranous flap which is folded on 

 itself at the sides, making there knobbed triangular projec- 

 tions. These projections, plainly seen from above, are 

 characteristic of the genus. 



Thorax. — The prot hoi-ax bears on the dorsum two minute 

 hairs anteriorly. There is a short bristle at the angle and 

 one hair at each side on the posterior edge. The metatJiorax 

 bears two minute bristles anteriorly. The long bristles at 

 the angle and posterior edge, which are about five to six in 

 number, are placed in a row on each side with a clear space 

 at and near the apex. On the sternum the chitinous bands 

 between the posterior coxae are specially well marked, four 

 hairs on sternum, two between mid coxae and two between 

 hind coxae. In colour the thorax is clear brown with darker 

 margins. In the prothorax there are (according to the age 

 of the individual) more or less indications of a clear median 

 space in the dorsal spot. The thorax in both sexes is 

 rounded over the abdomen. 



