Bypophaga.- 



-INSECTS.- 



-Bkachelytka. 



207 



ait Prosterniim joined behind with the metasternum. 



Posterior coxsi furnished with plates partly covering 



the abdomen, .... Halipl'uks. 



Posterior coxie without plates, . . Pelubicks^ 



II. Posterior coxae very large, widened in front. 



b Four anterior tarsi, furnished with only four joints, 



ilydroporules. 

 bb All the tarsi furnished with five joints. 



The dilated joints in the males simple, with small 



cupules of equal size, . . Colyinbctidcs. 



The dilated joints of males in the form of a great 



fiuhorbicular palette, with small cupules of unequal 



They are all included by Mr. AVatcrhouse in the 

 family Dytiscidce. lie gives one hundred and eleven 

 species as natives of the British islands. They are in 

 the genera Dyliscus, AcUius, Hydaticus, Colymbctes, 

 J/ijhius, Agabus, Noterus, Laccophilus-, liyphidrus, 

 Ilydi-oporiis, HaUplus, Cnemidotus, and Pelobius. 



The Dijtiscus marginalis is a common species in 

 this country, and is so named from the conspicuous 

 yellow margin of the thorax. Water-beetles fly about 

 at niglit, and frequently in moonlight nights dash them- 

 selves against glass-windows, which they seem to mis- 

 take for pools or streams. 



These water-insects are very carnivorous; their larvae 

 are often very beautiful objects for the microscope. 



Family— GYRINID^ ( Whirlwhkjs). 



Who has not seen the Whirh;bigs gyrating on a 

 pool or river — as if they did not toucli the water ? 

 Some of the exotic species are of considerable size, 



Fig. 64. 



a Hind leg of a species of Gyrinus. b Antenna. 



and are curiously formed. Others have pointed bodies 

 and elytra. Their antenna; and legs are very curious. 

 Of the figures a is that of the hind leg; h that of the 

 antenna. 



Sub-section— RYPOPHAGA (Cleansers). 



The next sub-section of the Pentamera has been 

 named Rypophaga, from the insects contained in it 

 eating putrid animal and vegetable matter, and in 

 this way cleansing and clearing the ground. Tliey 

 have only four palpi, and the antenna in most of 

 them are either gradually or suddenly clavate. In 

 those which inhabit the water, the maxillary palpi are 

 generally of considerable length ; and these organs, but 

 for their having fewer joints, might be taken by the 

 beginner for their antennse. In one large section of 

 the group, the elytra are extremely short. This section 

 is iirmed Brachdytra. 



Gkoup— BEACHELYTRA. 



Generally longish beetles, with very short elytra, 

 though a few of them are very short insects, and have 

 elytra nearly covering the abdomen. 



There are at least two thousand species known of 

 this extensive group of beetles. In fact, the greater 

 portion of the above are European ; six hundred are 

 recorded as British in Mr. Waterhouse's Catalogue of 

 British Coleoptera. It has been said that they are com- 

 paratively rare in the intertropical regions; this seems, 

 however, to arise from their not having been so much 

 searched for as other groups. 



The following is the arrangement of the group in 

 the monograph of Ericbson, an arrangement which is 

 generally adopted by all naturalists : — 



I. Prothoracic stigmata visible, seldom covered by a homy 

 free plate, 



Antenna; inserted at the inner margin of the eyes, 



Alcocliorida:. 

 Two hundred and sixteen of these are British. 



Antennje inserted below the side margins of the front, 



Taclujporiili:^. 

 Fifty-five are British. 

 Antenna; inserted on the fore margin of the epistome, 



jSt(q)hi/liniu(E. 

 Mr. Waterhouse divides this, as Kraatz does, into 

 Quediidfe and Staphylinidse — with one hundred 

 and six British species. 



II. Prothoracic stigmata concealed by the epimcra of the 

 prothorax. 



A. Posterior coxs conical. 



a A membranous space between the fore-coxa;, Pccderidfc. 

 Xantbolinida; and Ptcderidje have fifty-seven recorded 

 British species. 

 aa Prothorax quite horny below. 



Antennee inserted below the side margins of the 

 front, ...... riitophlliflw. 



Antennje inserted on the front, . . . ^'icnida:. 

 There are fifty British species. 



B. Posterior coxa; transverse- 



b The anterior coxje globular, not prominent, Ficstiilce. 

 Only one British species. Some of the exotic species 

 are fine and large. 

 hh The anterior coxae conical, prominent. 



c No ocelli. 



Abdomen seven-jointed, . . . Oxijldidm. 



There are forty-nine British species. 

 Abdomen six-jointed, . . . Phlicochariflm. 

 cc Front with two ocelli, .... Omalidcc. 

 There are forty-three British Omalida:. 

 bib Anterior coxfe sub-cylindrical, transverse, Proteiniila. 

 There are nine British species. 

 Of the little pretty Micropeplida;, with their curiously- 

 pitted elytra, there are four British species. 



We here figure from Erichson's work the Scy- 

 talinus serpcntinus, Tanygnatlms termincilis, and the 

 very curious Megalops cephaloks (figs. 65, CG and 67), 

 which, with the other figures, show the great variety 

 of form amongst the Brachelytra. 



In their perfect state StapliylinidM chiefly feed on 

 decaying animal and vegetable substance. Many of 

 the species which are found on flowers or in fungi 

 seem to be carnivorous ; the former frequent the flowers 

 on accotmt of the small insects which they find tliere, 

 while the latter feast on the grubs which aboinid in fungi. 

 These insects are accordingly found in many dillercut 



