ANOPLDRORUM BRITANNIA. 127 



merits black ; legs pale yellow, rather stout ; anterior femora 

 sub-angular. Length f. 



Communicated by Mr. Tweedy of Truro, from the Oys- 

 ter-Catcher (Haematopus oestralegus). 



20. NIRMUS SELLATUS. (Louse of the Common Tern.) 



Plate VII. Fig. 5. 



Pearly white, smooth and shining ; head, thorax, and 

 abdomen, with a dark margin, the segments of the latter 

 with a dark sub-lunar mark in the centre. 



Nirmus sellatus. Burmeister Handbuch ii. pt. ii. p. 428. spe. 6. Pedi- 

 culus Sternae? Linn. Syst. Nat. ii. 1019.21. Faun. Suec. 1953. 

 Fabr. Syst. Ent. 808. 22. Syst. Inst. ii. 486. 26. Stew. Elemt. ii. p. 

 299. 22 Ricinis Lari? Degeer. Inst. 7. 77. 4. tab. 4. tig. 12. 



Head and thorax pale yellow-white, the former sub-tri- 

 angular and obtuse, with a black sinuated margin inter- 

 rupted at the clypeus, with two short fasciae extending to the 

 vertex, and an impressed oblique line from the antennae to 

 the occiput ; tr abeculae small and acute ; antennae short and 

 slender, the last three joints the darkest; prothorax very 

 small, transverse ; metathorax as wide as the head, lateral 

 margin oblique, with a broad black band, posterior margin 

 acutely angular in the centre ; abdomen claviform, with a 

 black dentate lateral margin, the 3rd, 4th, 5th, and 6th seg- 

 ments generally with pitchy semilunar marks, and a black 

 spot in the centre ; legs short and robust, with a pitchy 

 annulus at the extremity of the femora and tibiae; tarsi 

 chestnut. Length 1 . 



This species is subject to great variety in the markings of 

 the abdomen. I have received specimens of this insect 

 from the Kittiwake Gull, through Mr. Tweedy of Truro ; 

 from the Herring Gull (Larus argentatus) and Black-headed 



