CLASS V. INSECTA. 157 



and whe4i perfect, living on other insects. Tlie anterior and middle 

 tarsi in some of the genera have but tour joints. 



A. With a scutellum, feet formed for walking : tarsi, the whole of 



the in with five joints; claws didactyle. 



Sti rps 1. — Hinder thighs covered at their base with a shield-shaped plate. 

 Genus 51. IIALIPLUS. Latr., GylL, T^ach. Cxemidotcs. Illig. 

 HoPLiTUS. Claire. 

 " * Bodi/ ohlong oval. Ehjtra with elevated ridgcsS^ Leach. 



Labial and external maxillary palpi subulate. 

 Sp. 1. llul. elcvatus. Panz. 

 Inhabits running streams. 



" ** Body oral. Elytra striated.'" Leach. 



Sp. 2. Hul. ferruginens. Linne. 

 Inhabits ponds and ditches. 



Stirps 2. — Hinder thighs w'whowt the shield at their base: (n/^s pro- 

 minent.) 



Genus 55. PVELOBIUS. Schonherr, Leach. Hygrobia. Lalreilk. 

 IIydrachna. Fair. 

 External maxillary palpi with the last joint subclavate. 

 Sp. 1. Feel, llermanni. Black: head, transverse band on the thoiax, 

 base and border of the elytra and feet ferrugineous. (P/. ^.fg. 1-4-) 

 Dytiscus Ilermaimi. ^Lirsh., Oliv. 



Inhabits ponds. The last segment of the abdomen when rubbed 

 against the elytra produce a noise. 



B. Scutellum none. Feet, hinder ones, for tlue most part foryied for 



siciinming. 



Stirp's 3. — The four anterior tarsi with four, the two posterior with 

 five joints. 



Genus 5G. Hvphydrus. Latr., GylL, Illig., Schunh., Leach. 

 Body nearly globose : the four anterior tarsi with the last joint short; 



the hinder feet witli but one claw. 

 Sp. 1. Hyp. ovutiis. Obscure, ferrugineous, impunctate; the base of 



the elytra with an impression at tlie base of the suture. 

 Dytiscus ovatus. Limit. 

 Inhabits ponds. 



Genus 57. HYDROPORUS. Clairvilk, Leach. IlYPUYPRrs. 

 Illig., Schunh., Gyll. 

 Body otal ; the breadth exceeding the height : the four anterior tarsi 

 with four joints, the last joint slender: claws didactyle. 



