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INTRODUCTION. 



These extraordinary little insects, of which three or four species 

 are known from Spain and North America, are really Trtcho- 

 PTEKYGiDiE modified for an aquatic existence. They appear to be 

 found in running water. 



[Family 20. SPH^ERIID.E.] 



Minute hemispherical insects; head large, sessile, with the eyes 

 large ; antenna; short, W-jointed, with the club well marl: ed, obscurely 

 ^-jointed; maxilla: feeble, bilobed ; ivings large and ample, deeply 

 fringed ivith cilia ; episterna of the metasternum long and narrow ; 

 all the coxa: transverse ; the posterior pair very much enlarged, 

 prominent, contiguous, extending to the sides of the body and to the 

 fourth ventral segment. 



The Sphjeriid.e, through their ciliated wings, are evidently 

 allied to the Trichopterygldj2, but apart from this, they present 

 no special affinity to any particular group, as pointed out by 

 Mr. Matthews, who took a great interest in this small family, and 

 described four out of the six known species. In one or two 

 points they are, perhaps, related to Cercyon. Their chief character 

 is found in the great development of the posterior coxae. As far 

 as at present known they are entirely confined to Europe, and 

 North and Central America. 



Family 21. CORYLOPHI1LE. 



Minute insects ; antenna: with the first or the two basal joints 

 enlarged, 8- 9- 10- or W-jointed, clavate ; maxillce with one lobe, the 

 palpi being of extraordinary form, with the second joint much 

 dilated ; abdomen with six free ventral segments; tarsi four-jointed, 

 apparently three-jointed, the third joint being very minute and 

 concealed by the emarginate or notched second joint. 



The chief points in this group appear to be the extraordinary 

 form of the maxillary palpi (in many instances), and the abnormal 

 and irregular antennae in several of the genera such as Aniso- 

 meristes and Mkrostagetus. The number of joints is very variable, 

 Oligarthrum possessing 8 joints only, Corylophus and Arthrolips 9, 

 Sericoderus 10. and Sacium 11 ; the maxillary and labial palpi are 

 large, with the second joint much dilated ; the wings are fringed 

 with hairs but very much less deeply than in the Trichopterygid^;, 

 und the veins are obsolete except at the base. 



The larvae of Ortlioperus piceus and Arthrolips piceus have been 

 lescribed by Perris ; they are elongate-oval, the latter being shorter 

 and broader, with a very small head and the prothorax much 



