Mecistocephalidae Bollman, 1893

Diagnosis from Bonato et al. (2003: 547-548)^[1]:

Body slightly depressed, uniformly wide in its anterior three quarters but tapering backwards. Adult body length from c. 2 to 14 cm. Colour from pale yellow to red-brown, head and forcipular segment darker. Antennae 2–3 longer than head, distally attenuated. Antennal setae increasing in density from basal article to tip of appendage. Cephalic plate subrectangular (length to width ratio 1.2–2.1), frontal line usually present. Clypeus subdivided into an anterior areolate part and a posterior part which is virtually not areolate (plagula/ae). Buccae areolate in the anterior part only, internalmargin thickened (stilus). Labrum composed of a mid-piece and 2 side-pieces, each side-piece divided by a transverse thickened line into an anterior and posterior ala. Paralabial sclerites not recognizable. Mandible only provided with a series of pectinate lamellae. First lamella similar to other lamellae but smaller, last lamellae rudimentary. Mandibular basal tooth conical. Coxal projection of first maxillae similar in shape and extension to the corresponding telopodite, both of them being uniarticulate and composed of a sclerotized base and a hyaline distal part, without any additional lobe. Coxosternum of second maxillae usually undivided, areolate in the median part and always provided with a pair of metameric pores. Telopodite of second maxillae triarticulate, usually provided with a reduced claw. Forcipular tergum narrower than cephalic plate, partially covered by the latter and by tergum of first leg-bearing segment. Forcipular pleura widely visible from above, each provided with a dorsal setigerous ridge and ending anteriorly in a pointed scapula. Forcipular coxosternum wider than cephalic plate, its antero-external parts visible from above. A pair of tiny teeth on anterior margin of forcipular coxosternum. No chitin-lines. Forcipular telopodites rather large, clearly visible from above beyond lateral margins of cephalic plate, usually also in front of same. Forcipular tarsungulum relatively long. Forcipular trochanteropraefemur with a distal, sometimes also a proximal tooth; intermediate articles often with a tooth each. Poison calyx elongate, usually reaching distal part of trochanteropraefemur. Terga of leg-bearing trunk with 2 paramedian sulci, fading in most posterior segments. Sterna of leg-bearing trunk with an internal apodema and a midlongitudinal sulcus, fading in posterior segments. Anterior sterna with a posterior endosternal process, gradually reduced in size in posterior segments. First pair of legs shorter than following pairs. Tergum and sternum of last leg-bearing segment rather elongate. Coxopleura covered by 10s of circular pores. Telopodite of last legs of 6 articles, thin (although sometimes slightly swollen in males) and longer than telopodite of remaining legs. Praetarsus of last leg extremely reduced. Posterior part of last sternum and ventral internal margins of coxopleura covered by dense pilosity. Gonopods biarticulate. Anal pores usually present.

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