16 DIPTEEA. 



1. Pachyrrhina ordinaria, sp. n., <s $ . 



Head orange-yellow above ; rostrum with a more or less distinct brown spot above ; an arrow-shaped shining 

 black spot on the vertex, the point of which is drawn out in a line towards the front ; a small black or 

 brown mark on the inner orbit of each eye. Antennae black, the first and third joints reddish or brownish at 

 the base ; in some specimens, principally females, the two basal joints are altogether yellow. Thorax yellow, 

 with uniformly deep black shining stripes ; the lateral ones straight, not incurved towards the dorso- 

 pleural suture ; a brown line (sometimes obsolete) on each side of the collar ; a similar line above the 

 dorso-pleural suture, a little in front of the root of the wing ; pleurae sulphur-yellow, with yolk-yellow 

 spots; scutellum yellow; metanotum sulphur-yellow on the sides, reddish or brownish-yellow in the 

 middle. Abdomen reddish-yellow, with a more or less broad black dorsal stripe (in some specimens it is 

 uninterrupted, in others it is broken up at the incisures into a series of spots, which are often triangular), 

 and a trace of a black or a brown stripe on the lateral margins ; genitals reddish-yellow. Legs more or less 

 brownish or reddish-brown, except the coxae and the proximal half of the femora ; sometimes the femora 

 are altogether reddish-yellow, except at the tip. Halteres pale brownish. Wings greyish-hyaline; 

 stigma pale, brownish-grey ; second posterior cell coarctate at the base, sometimes even short-petiolate. 



Length : rf , 10-11 millim. ; 2 , 12-13 millim. 



Hab. Mexico, Ciudad in Durango (Forrer). Three males, two females. 



2. Pachyrrhina nigrolutea. 



Pachyrrhina nigrolutea, Bellardi, Saggio &c. i. p. 11. 



Head orange-coloured above, with a broad arrow-shaped shining black spot in the middle (the point of which is 

 not drawn out in a line), and some black marks on the inner orbit, of the eyes ; rostrum yellow, with a broad 

 black stripe above, not touching the base of the rostrum ; antennae black, the first joint more or less reddish. 

 Thorax yellow, with the usual black shining stripes ; the lateral ones are incurved towards the dorso- 

 pleural suture, where they assume an opaque, velvety-black colour ; both ends of the mesothoracic suture, 

 above the root of the wings, are marked with the same velvety-black, which, in a favourable light, can be 

 seen on the black shining ground of the posterior end of the lateral thoracic stripes ; the pleurae are 

 yellow, with a number of black spots and stripes ; a large black angular spot above the sterno-pleural 

 suture, its upper lobe pointing towards the root of the wing ; a black stripe along the mesopleural suture 

 runs from the root of the wing downwards ; its lower end is connected on one side with the angular spot, 

 and on the other with a large horseshoe-shaped black or brown spot running round the yellow metapleura ; 

 the posterior end of the latter spot expands round the point of insertion of the haltere and bifurcates beyond 

 it, sending one branch to the middle coxa, the other to the hind one ; a large black spot on the sternum, 

 between the front and middle coxa), and a similar smaller one between the middle and hind coxae, both 

 encroach upon the extreme base of the coxae ; scutellum black ; metanotum black in the middle, yellow 

 on the sides ; knob of the halteres bright yellow. First segment of the abdomen reddish-yellow, with a 

 narrow black hind margin ; second segment reddish-yellow on its anterior portion, the remainder black ; 

 the following segments are like the second, the yellow and black thus forming alternate cross-bands, the 

 yellow ones being narrower. Wings with a pale yellowish-brown tinge, more yellow on the costal cells ; 

 stigma pale brown ; second posterior cell subsessile or short-petiolate, attenuate at the base. 



Length ( $ ) 11-12 millim. 



Hab. Mexico, Orizaba (Sumichrast) ; Costa Rica, Rio Sucio, Irazu 6000 to 7000 

 feet (Bogers). 



The yellow tinge of the costal cells is the characteristic mark of this species. I have 

 compared Professor Bellardi's types, and give a somewhat fuller description. 



