muir: two new species of ascodipteron. 355 



spiracles do not appear to join one another, or to be in communication 

 with the dorsal ones, but each sends off two or three longitudinal 

 branches. The four dorsal ones join and form a reticulation a little 

 beyond the spiracles, then continue as four main longitudinal branches, 

 which proceed to the various organs of the body and send off small 

 branches to the muscles. I can trace no other spiracles in the abdo- 

 men. In the thorax there is a large spiracle in the episternum and a 

 small and very obscure one near the halteres I could not follow the 

 connection between the abdominal and thoracic tracheae through 

 the small abdominal foramen. 



The head and thorax can be moved forward and backward so that 

 the end of the proboscis can be thrust out of the mouth of the invagi- 

 nation. They are greatly distended and appear as one, owing to 

 the large occipital foramen and the distention of the membranes 

 (Plate 1, figs. 3, 4). The various sclerites are isolated, often partly 

 concealed by the distended membranes overlapping their edges, 

 especially between the gena and the front and face. The basal 

 stumps of the wings are present (Plate 1, fig. 3, w), the halteres are large 

 and intact (Plate 1, fig. 4, h) the legs are missing beyond the trochanter 

 (Plate 1, fig. 4, t). The most conspicuous part of the head is the large 

 thick proboscis (Plate 1, fig. 3, p) which projects forward, bearing four- 

 teen sets of chitinous blades at the end. This proboscis is unique 

 among flies, but I hope to show that it is a modification of a normal 

 muscid type developing along certain lines indicated in certain other 

 species of Pupipara. 



The larva. The full-grown larva is about 1.5 mm. long and 1 mm. 

 across the largest diameter, oval, semitranslucent and pearly white 

 (Plate 1, fig. 5). On the posterior end there are four curved, chitinous 

 ridges, the spiracles, which under a lens of high power appear ser- 

 rated; the dorsal is longer than the ventral pair. Between the ante- 

 rior ends of the ventral pair is a small dark spot, the anal mark. 

 At the anterior end, in a slightly ventral position, is a small opening 

 leading to the stomach; no mouth-hooks are present. 



Upon examining the larva in certain lights the tracheae can be dis- 

 tinctly seen (Plate 1, fig. 5). The spiracles on each side give off large 

 tracheae which meet and continue to the anterior end, giving off 

 ten dorsal and ten ventral branches. The first dorsal branch, count- 

 ing from the spiracles, runs backward and does not coalesce with its 

 fellow on the other side; the following six coalesce with those on the 

 opposite side, while the three anterior ones do not. The first ventral 

 branch runs backward and, along with the following five, which join 



