Mouth-parts in Plectrotarsus and JEthalopteia. 25 



the rest of the liead, which is the case in all the Ilydro- 

 ))sychi(lte luul allied families. 



Anteitmc. — Extremely long an 1 slender. Basal joints 

 stouter than the rest. 



Muuth-parts, — These are not easy to see without special 

 preparation, being sitnated in a small hexagonal area beneath 

 the lower margin of the long clypeus. They are small and 

 insignificant (tig. 2). They consist of: — 



(1) Labrum. — 'I'his is roughly triangular, and, like the 

 rest of the paits, thinly chitinized. 



(2) Mandibles. — Of an extraortlinary character. Each 

 consists of a large basal part, which suddenly narrows, to 

 end in a very long, thin, somewhat irregidarly shaped splint- 

 like piece of chitin, the extreme tip being sharply pointed 

 and more firmly chitinized than the rest of the mandible or 

 any other of the appendages. No condyles are present and 

 there is no trne articulation, as the mandible grows out from 

 the angle on one side of the labrum, and shows no trace of a 

 joint or suture between it and the head. There are two 

 elongate hairs on the basal part of the mandible. 



Tlie rest of the mouth-parts consist of: — 



(3) A median elongate lobe, with 



(4) two small lobes on either side of it, and 



(5) two broad flat lobes or semicircular " ledges," forming 

 a kind of lower lip. 



The median lobe I regard as the haustellum, and the two 

 lateral lobes are almost certainly the lobes of the first pair of 

 maxillse. In all Trichoptera the first maxilla possesses only 

 a single lobe. The two ledges perhaps represent the labium. 

 Lal)ial and maxillary palpi are completely absent. All these 

 parts are delicate and thinly chitinized, so that one is induced 

 to believe them to be the atroj)hicd remnants of mouth-[)arts 

 now quite function less. 



The Head of Plectrotarsus gravenhorstii 

 [Family Sericostomatidse) . 



Ulmer (6) has given an interesting note on this peculiar 

 Australian insect, iji which he shows that tlie so-called 

 *' proboscis" stands in no relation with the lower lip, but is 

 " .sicherlich als Aidiang oder Fortsatzdes Labrum anzusehen." 

 Hiigen (7), in 18^1, had written that when the mouth-parts 

 of tlie Phryganeidaj are spoken of in general as short ones, " it 

 must not be forgotten that there exist genera with a deve- 

 loped proboscis much longer than the head, and certainly fit 

 lu enter fiowers ; the greatest development I know of among 



