POLYMORPHA 243 



joints SO delicately connected that the organs are rarely un- 

 niiitilated. 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 he associated with 

 Dascillidae. Nothing is kno^vn as to the earlier stages. They 

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

 America. 



Fam. 45. Cyathoceridae — 2Iinute Insects of hroadform; parts 

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

 into joints ; jj'i'ostermuii snudl. 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, clubhed ; tarsi four- 

 jointed ; i^rosternuni very small; front coxae cxserted, hut not 

 contiguous. Tliere are about two dozen species of these small 

 beetles known. Our British Georyssus ■pyyniaeus lives in extremely 

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

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

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

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

 globe. 



Fam. 47. Heteroceridae. — Lahrum and mandiUes irrojecting 

 forwards; antennae sJiort, the tcrmi7icd seven joints broad and short, 

 forming a sort of broad serrate club ; legs armed vith 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 

 uljdomen, 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. — Prostermcm distinct in front of the coxae, 

 usually elongate, beJil/ul forming a process received into a definite 

 cavity on the mesosternuin ; head retractile, the mouth protected, 

 by the prosternurn. Tarsi jive -jointed, termincd joint long. 



