Rhantus.] ADEriiACA. 201 



SHANTUS, Lacordairc. 



Tliis genus comprises about forty known species, although there are 

 a good many more assigned to other genera that probahly belong to it ; 

 they are widely distributed throughout the world, there being very few 

 parts where the genus is not represented by one or more species. 



I. Base of thorax sinuate on each side near posterior angles ; 



colour black R. GEArii, Oi/ll. 



II. Base of thorax almost straiijht ; upper side more or less 

 testaceous. 



i. Under side entirely testaceous R. exolettjs, Forst. 



ii. Under side wholly or partially black. 



1. Thorax with a tiansverse dark spot on disc. 



A. Antennaj entirely testaceous ; abdomen uni- 



colorous black R. PULVEEOSTTS, Sleph. 



B. AnteuuiD with last joints ringed with black ; 



abdomen more or less testaceous R. kotATUS, Berg. 



2. Thorax with anterior marjjin narrowly and poste- 

 rior margin broadly marked with black ; first ab- 

 dominal segment black R. bisteiatus, Berg. 



3. Thorax unicolorous red, or at most with small 

 markings on posterior margin darker ; first abdo- 

 minal segment testaceous R. ADSPEESTTS, F, 



It. G-rapii, Gyll. Oval, rather depressed, somewhat long and 

 narrow ; black, upper surface very closely and finely reticulate and 

 rather dull ; antennae and palpi testaceous ; legs more or less pitchy ; 

 margins of thorax and elytra obscurely pitchy-brown; thorax strongly 

 sinuate at base on each side, so that the posterior angles are produced ; 

 iiiternal posterior claw double as long as the external ; male with the 

 front and middle tarsi thickened and compressed with four rows of 

 small palettes. Long. 11, lat. 5j mm. 



Ponds, &c. ; local, but not uncommon where it occurs ; London district, Lee, Birch 

 Wood, Reigatc, Forest Hill, Horsell, Woking; Horning Fen, Norfolk ; Cambridgeshire 

 Fens ; Askham Bog, York (common at certain seasons of the year) ; not recorded 

 from the extreme north of England or Scotland. 



This species is often confounded by beginners with Agahus hipnxlii- 

 latus, and species of Ilijhius ; from the former it is at once distinguished 

 by its sculpture, and from the latter by its elongate and depressed form. 



B.. exoletus, Forst. Oval, slightly convex ; head testaceous, Avith 

 dark markings more or less distinct ; antennae testaceous, apical joints 

 partially Iduck ; thorax testaceous, unicolorous or with two dark spots at 

 base touching basal margin ; elytra testaceous variegated with close and 

 fine dark markings which are more or less confluent and cover the whole 

 surface except margins and extreme ba.se ; upper surface very finely 

 reticulate, elytra with more or less distinct rows of larger punctures ; 

 legs testaceous ; male with the front tar.'^i rather thickened and a good 

 deal compressed with moilerately large palettes ; sculjiture of the sexes 

 identical : the species is easily distinguished by the testaceous under- 

 .side. Long. 10, lat. 5.1 mm. 



