POLYMORPHA 243 



joints so delicately connected that the organs are rarely un- 

 mutilated. The modifications of the head and prothorax are 

 quite unlike those of other Byrrhidae, and if the Chelonariides 

 do not form a distinct family, they should be associated with 

 Dascillidae. Nothing is known as to the earlier stages. They 

 are chiefly tropical Insects, though one species is found in North 

 America. 



Fam. 45. Cyathoceridae Minute Insects of broad form; parts 

 of the mouth concealed ; antennae four-jointed ; tarsi not divided 

 into joints ; prosternum small. The only species of this aberrant 

 family, Cyathocerus horni, has been found in Central America. 

 Nothing is known as to its life-history. 



Fam. 46. Georyssidae. Antennae short, clubbed ; tarsi four- 

 jointed; prosternum very small; front coxae exserted, but not 

 contiguous. There are about two dozen species of these small 

 beetles known. Our British Georyssus pygmaeus lives in extremely 

 wet places, and covers itself with a coating of mud or fine sand 

 so that it can only be detected when in movement. Nothing 

 further is known as to its life-history or habits. Members of 

 the genus have been detected in widely- separated parts of the 

 globe. 



Fam. 47. Heteroceridae. Labrum and mandibles projecting 

 forwards; antennae short, the terminal seven joints broad and short, 

 forming a sort of broad serrate club ; legs armed with stout spines ; 

 tarsi four-jointed. The Heteroceridae are small beetles covered 

 with very dense but minute pubescence ; they live in burrows 

 among mud or sand in wet places, and are found in many parts 

 of the world. They possess a stridulating organ in the form 

 of a slightly elevated curved line on each side of the base of the 

 abdomen, rubbed by the posterior femur. The larvae live in the 

 .same places as the beetles ; they have well-developed thoracic 

 legs, the mandibles are porrect, the three thoracic segments 

 rather large, and the body behind these becomes gradually 

 narrower ; they are believed to eat the mud amongst which 

 they burrow. We have seven British species of Hetero- 

 ceridae. 



Fam. 48. Parnidae. Prostermim distinct in front of the coxae, 

 usually elongate, behind forming a process received into a dejinite 

 cavity on the mesosternum ; head retractile, the mouth protected 

 by the prosternum. Tarsi Jive -jointed, terminal joint long. 



