514 .STUDIES iX LIFE-HISTORIES OF AISTRALIAX DIPTERA BRACHYCERA, i.. 



ence. Others, covereil witli a thin hiyer of sandy soil, which, owing to evapora- 

 tion, soon became quite dry, were still alive, and quite healthy after several days. 

 But larvae which had been placed in small porous flower pots, planted with grass, 

 were found rjuite dead, dry and shrivelled, together with the grass, when, owing 

 to a week's enforced neglect, the soil had been allowed to become dry and caked 

 hard. Returned to damp conditions none of them showed any signs of reaniina- 

 tion. In their powers of resistance to desiccation, therefore, they are strikingly 

 different from the aquatic species of Stratiomyia observed by Cros (1911), and 

 by Laker (1880). The former records having kept larvae of Stratiomyia 

 anubis in a phial containing 15 mm. depth of completely dry sand for seven 

 months l)efore the emergence of the imago. And Laker found a living larva 

 of a Stratiomyia sp. in the dry sand at the bottom of a box formerly used as 

 an aquarium, after it had been emptied of water, and stored in a cellar for fully 

 three months. 



Description of the larva. 



The larvae are very similar in general appearance to those of the genus 

 Sargus Fabr., as described by Brauer (1883), and Lundbeek (1907). But the 

 Sargus larva, like those of all other Stratiomyids, is said to have only eleven 

 post-cephalic segments, whereas a lateral view of Metoponia ruhricepa shows that 

 twehe segments are actually present. From a dorsal aspect only eleven seg- 

 ments are seen (Text-fig. 1), and in ventral view another segment is not readily 

 distinguishable. But, when viewed laterally, it is seen that what appears to be 

 the terminal segment, consists, really, of the imperfectly fused eleventh and 

 twelfth, the twelfth segment being directed ventrally, and di^'ided off from the 

 eleventh by a very oblique line (Text-fig. G). 



The segments are all much broader than long, and of uniform width from 

 the second to the tenth; the terminal segments are slightly narrower. The bodv 

 is elongate, and, in the older larvae, flattened dorso-ventrally. Younger larvae 

 are more nearly cylindrical, larvae of 4 mm. length having a lateral diameter 

 of 1.0 mm., and a dorso-ventral of .93 mm., whereas the corresponding propor- 

 tions in a larva of 9 mm. length are 2 . and 1 . 6 mm . In transverse section 

 the segments have the shape of a bi-convex lens, with the lateral edges expanded 

 into tumid ridges, marked off from the main body, on both surfaces, by a shal- 

 low groove. The eleventh segment is somewhat spatulate, with a median and 

 two lateral convexities on the dorsal surface (Text-figs. 1 and 15). Between 

 the segments, the body is slightly constricted, and, in contraction, the segments 

 .ire imbricated, overlapping from behind forward in front of the fourth segment. 

 and in the reverse direction from the fourth backward. The incisure between 

 the tenth and eleventh segments is strongly arched forwards (Text-fig. 1). 



At the anterior extremity is sit\iated the dark brown, strongly chitiniscd 

 head, which can be retracted into the first thoracic segment. 



Integument. — The whole body is invested in a thick, firm integument of the 

 typical stratiomyid type, consisting of large hexagonal plates, separated by 

 granular areas, w'lich cause a grating sound when scratched with the point of a 

 needle (Text-fig. 9) This armoured coat is strongly impregnated with car- 

 bonate of lime. Fixation in Carl's fluid, containing glacial acetic acid, gives 

 rise to a rapid and long continued evolution of gas, proved, with baryta water, 

 to be CO2. Along the posterior nuirgin of each segment (Text-fig. 10) are 

 two or three transverse rows of specially differentiated amber-coloured plates 



