586 INSECTA MADEREXSIA. 



punctiilatcd ; whilst its comparatively quadrate head and more subulated palpi 

 AvUl serve additionally to characterize it. It is apparently extremely rare, the 

 only specimen which I have seen having been captured by myself at the edges of a 

 small stream at Santa Anna {in the north of the island) dm-ing the summer of 1850. 



(Subf. 4. P^DERIDES.) 



Genus 201. ACHENIUM. 

 (Leach) Curtis, Srit. Ent. iii. pi. 115 (1826). 



Corpus mediocre, elongato-lineare, valde depressum : capite quadrato-obcordato porrecto exserto ; 

 oculis parvis rotundatis demissis : prothorace trapeziformi (antice latiore), angidis anticis leviter 

 exstantibus : alis plerumque amplis : ahdumine liueari margiiiato, segmento sexto in maribus 

 subtus triangulariter emarginato. Antenna sub froutis margine insertoe, rectse, tiliformes (aut 

 apicem versus etiam subattenuatse), articulo prime lougiusculo robusto subcylindrico, secundo 

 breviore, ultimo acuminato-ovato. Labrum amplum, profunde bilobum, lobis divergentibus et 

 ])ilis longissimis munitis. Mandibula minus elongata;, in medio fortiter unidentatie, apice valde 

 incurva; acutse. Maxilla bilobte : lobo exierno corneo, apice membranaceo barbato : interna 

 membranaceo, intus dense pubescente. Palpi maxillares articulo primo minuto, secundo et tertio 

 longitudine subaequalibus (hoc apicem versus leviter incrassato), ultimo minimo obtuse subulato ; 

 labiates articulis primo et secundo subcylindricis (hoc paulo longiore crassiorc), ultimo tenui sub- 

 ulato secundo breviore. Mentum breve transversum. Liyula brevis biloba ; paraglossis coriaceis, 

 ligulam baud superantibus. Pedes breves robustissimi [antid incrassati, femoribus subdentatis, 

 tibiis mtus sinuato-cxcavatis) : tibiis (sed prKsertim pustei-ioribus) subsetuloso-pubescentibus : 

 tarsis 5-articulatis {anticis in utroque sexu valde dilatatis et subtus tomcntosis) ; posteriuribus 

 teuuibus, articulo primo brevissimo, secundo tertioque longioribus, quarto brevi, ultimo his 

 conjunctis longitudine sequali. 



The extraordinarily depressed body of Achenium, in conjimction with its trapezi- 

 form prothorax, its somewhat squarish-obcordate head and its greatly thickened 

 legs, will at once serve to distinguish it, not only from its nearest ally, Latlirohium 

 (with which in most of its details it is coincident), but hke^vise from the remainder 

 of the Brachelytra here described. The few species (hitherto detected) which 

 compose it arc principally Eiu-opeau, and are more coimnon in central and Medi- 

 terranean latitudes than in northern ones. They are found generally in marshy 

 districts ; and I have usually observed that the A. depressum in our own country 

 (which is very nearly related to the Madeu-an A. Hartungii) is more especially 

 attached to muddy submaritime spots, — into the crevices of which (produced by 

 the heat of the sun) its flattened body enables it to retreat \vith facility, whilst its 

 exceedingly robust anterior legs, with then* broadly dilated feet (equally so in both 

 sexes), give it additional powers, not only for forcing its way through the narrower 

 clunks, but also for adhesion in crawling up their perpendicular sides (a structm'c, 

 be it remarked, Avliich is as much adapted to its peculiar mode of life as is the 



