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, dulled ; tarsi four- 

 jointcd; 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 u'ith stout spines ; 

 fi/rsi 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. Prosternum. distinct in front of the coxae, 

 iixinillil i-lniii'iate, behind forming a process receirnJ into a definite, 

 cavity on the mesosternum ; head retractile, 1 1/ c ///<///// protected 

 by the prosternum. Tarsi Jive -jointed, term i /ml joint long. 



