1923- Phillips. — The Larva of a Hydrophilid Beetle. m 



genus Megasternum appears to have been yet described, 

 some details of the structure of this interesting grub may 

 be of interest. I wish to thank Mr. McWhinncy for his 

 kindness in placing these specimens at my disposal, and 

 giving me the particulars mentioned above as to their 

 place of abode and time of occurrence. I would like also 

 to thank Professor G. H. Carpenter for the help and advice 

 that he has given me in the preparation of this paper, and 

 for the encouragement that he afforded me while working 

 in the zoological laboratory of the Royal College of Science 

 for Ireland. 



Description of the Megasternum larva. 



Head obovate as long as broad ; clypeus narrow, convex, 

 unidentate ; frontal processes short (fig. I, i), occiput with 

 medium groove (fig. I, i) ; hypostome narrow with rounded 

 base (fig. I, 6). 



Feelers with first segment twice as long as second, which 

 is a little longeo* than the third, terminal bristle elongate, 

 papilla on second segment stout (fig. I, 2.). 



Mandibles evenly rounded with acute apex ; right 

 mandible (fig. I, 4) with a single large, obhquely truncated 

 tooth and ridged surface internally; left mandible untoothed 

 (fig. I, 3), but with a series of six or seven backwardly 

 directed serrations on the inner edge ; each mandible with 

 two short stout bristles on the outer aspect near the base. 



MaxillcB (fig. I, 5), with cardo, broad stipes bearing 

 numerous spines externally, palpiger shortly cylindrical, 

 galea and lacinia vestigial ; palp with three segments the 

 terminal crowned with four small papillae. 



Labium (fig. I, 6) with small mentum, two-segmented 

 palps, and long, subtriangular hgula. 



Thorax with dorsal scuta ; pronotum well chitinised, 

 covering the segment ; mesonotum shorter and feebler ; 

 metanotum in two sections divided by linear membranous 



tract. 



Legs vestigial, represented by a pair of spiniferous tuber- 

 cles on the ventral surface of each thoracic segment (fig. 7). 

 No distinct segmentation is apparent in these vestigial legs, 

 each of which has a long bristle inserted on its inner aspect. 



