BORNEAN DRAGONFLIES. 59 
OroGoMPHUS DYAK Laidlaw. (PI. I. figs. 4-7.) 
Orogomphus dyak Laidlaw, Journ. Straits Branch R. Asiatic 
Sree IMINO jon, AU aN) 
@ Gc 
Venation :— 
The triangles of the hind wings have their upper and outer 
sides subequal, the inner side distinctly shorter, resembling that 
of the fore wing. 
Formula :— 
Anal | 
of hind ad Ann. Pn.n. M. Cu.  t. (cells). suprat. 
Dim ATT) | RE) GE esl es 
di(type).... —— 
eer MS 16a l= 15e OSS Go Talli beady 
5—4 
21—24, iM-—ahl 3—3 8 
ior) 
~ 
a 
| 
| 
| 
GB copsssoso === = 
8—6 16—18 12—13 3—3 U1 Nal 5—4 
The wings have a slightly yellow tinge, most marked when 
seen with reflected light, between Cu and M, proximal to the 
pterostigma, especially in the specimen marked @,,. 
Head: Uabium brownish yellow, labrum black; rhinarium dark 
brown, nasus bright lemon-yellow ; frons black, but with a fine 
yellow line along the crest which is surmounted by a number of 
fine black hairs, not so numerous as in O. atkinsoni. Vertex and 
occiput jet-black. Ocelli and antenne as in O. atkinsoni. 
Prothorax black above, the posterior margin edged with yellow, 
and the same colour on the sides. 
Thorax relatively small, black, marked with yellow lines. On 
either side is a narrow dorsal thoracic stripe, widening a little 
at its extremities, touching the mesothoracic half-collar below, a 
little curved with its convexity inwards; followed by a broader 
antehumeral stripe. There is a narrow stripe laterally on the 
metepisternum, and the metepimeron is finely edged with yellow ; 
the under surfaces are brownish, and there is a yellow interalar 
spot and a fine yellow spot on each alar sinus. 
Legs black, coxee and base of under side of femora of the first 
pair yellow. 
Abdomen black, marked with golden yellow as follows :—A fine 
transverse line at the distal end of 1; the distal half of 2, but 
this is largely obscured by a broad transverse black band lying 
within it; the auricles are yellow. There is a very small pair of 
lateral spots about the middle of 3, and a small terminal trans- 
verse spot on the same segment. On 6 there is a terminal ring, 
occupying about the last one-eighth of the length of the segment. 
The anal appendages are black, rather longer than 10. They 
resemble generally those of O. splendidus as figured by Dr. Ris, 
but differ in detail; the upper pair is much slenderer than in 
that species and has the ventral teeth much smaller; the lower 
