142 MK. EOBEET MCLACHLAN ON 



( = 19 mill.) excluding those organs, whicli themselves are 3J"' 

 (=7 mill.) long. Probably it has arrived at its last stage, 

 immediately before assuming the aerial condition of subimago, 

 the rudimentary wings extending slightly over the suture between 

 the third and fourth abdominal segments. The general colour 

 (as is usual with many aquatic larvae) is undecided, but may be 

 termed greyish-olive. The head is small, with simple hemi- 

 spherical eyes. The antennae in this individual are mutilated, but 

 probably they resembled those of the smaller specimen noticed 

 below. The frontal portion of the disk, above, forms a slightly 

 concave triangular space bordered by raised keels on either side ; 

 and these are continued as a single keel to the front margin, 

 which is rounded ; and when viewed from beneath, attached to it 

 is seen the transversely subquadrate clypeus, and the large labrum, 

 the front edge of which is very slightly rounded and raised and 

 with obsolete angles, the margins being slightly ciliated. The 

 mandiiles are very broad ; viewed from above there are two 

 strong blackish teeth on the outer angle, each divided into two 

 or more smaller teeth ; and to these succeeds a concave edge ; and 

 the inner angle and edge possess what seems to be a pectinated 

 fringe. Viewed from beneath the external teeth are still more 

 prominent, and they are succeeded by a long moveable testaceous 

 spine, the inner angle and margin being provided with a kind of 

 cup-shaped sucker formed by the dense pectinated fringe (if such 

 it really be) noticed above : the dentition &c., of the two man- 

 dibles is not quite symmetrical, that which frequently occurs in 

 insects. The maccillce are large and elongate, with strong teeth 

 on the apical portion, and with a false suture, giving them the 

 appearance of being divided into two longitudinal portions. The 

 maxillary palpi are 3-jointed, stout, all the joints nearly equal in 

 length, but each successively rather thinner. The labium is 

 deeply divided into four palpiform lobes, the two on one side 

 being curved in a direction opposed to those on the other, so that 

 the two inner approach each other at base and apex. The lalial 

 palpi are 3-jointed, very stout, the apical joint obtuse and con- 

 siderably shorter than the others. The pronotum is very narrowly 

 transverse. The mesonotum and metanotum are consolidated into 

 one large convex oval piece, with a median longitudinal suture 

 and two semilunate fovese posteriorly ; the posterior margin pro- 

 duced into a lobe. The rudimentary loings are elongate, ellipti- 

 cal, and with strong indications of veins. The abdomen is some- 



