1. PACHYGASTER 71 



North Europe to the Adriatic, and probably occurs over all Europe. The 

 metamorphoses are well known, and I quote from Macquart (Dipt, du 

 Nord de la France, 1826), "Ces larves, dit M. Carcel dans sa lettre d'envoi, 

 ' se trouvent dans le detritus du bois d'orme. Tant qu'elles prennent de la 

 ' nourriture, elles se tiennent dans la partie basse et humide. Je suis 

 ' sur qu'elles ont besoin de plus d'une annee pour leur doveloppement ; 

 ' mais je ne sais si ce terme va au-dela de deux ans, ce que je presume. 

 ' Pres de se transformer, la Larve s'eleve vers la surface, y reste immobile, 

 ' sans changer de peau, et passe a I'etat de nymphe. Sa depouille sert de 

 ' coque a celle-ci sans changer de figure. Si on I'ouvre on trouve cette 

 ' nymphe sous la forme de I'insecte parfait, mais ayant toutes ses parties 

 ' cnveloppees d'une mince pellicule, et n'occupant qu'une partie de son 

 ' domicile. Enfin la derniere transformation s'opere." 



Besides being bred from the detritus of the Elm (Uimus), it is said to 

 have been bred from Populus alba and Finns sylvcstris, but I do not feel 

 full confidence as to the larvae on these being those of P. atra, as they may 

 possibly have belonged to one of the other species. Also from what we 

 know of P. minutissima (P. pini Perris) it is very probable that the 

 " detritus " may be the frass of wood-boring Coleoptera ; though the meta- 

 morphoses of P. orhitalis, as proved by Dr D. Sharp's researches, are made 

 in the sodden-wet rotten wood of Holly {Ilex). 



3. P. tarsalis Zetterstedt. Wings rather blackened on the basal half. 

 Antennse brownish in both sexes, or sometimes orange in the female. 

 Back of the head but little inflated. 



The largest and stoutest European species. 



$ . Head about as long as deep when viewed in profile (fig 95). Face and frons 

 forming a small rather shining black triangle ; frons with a deep middle 

 channel, and the two consequent raised sides with a slight silvery shimmer 

 caused by minute closely adpressed pubescence ; face with very short and 

 very inconspicuous even though dense pubes- 

 cence ; jowls extremely narrow ; back of the 

 head a little inflated on the lower third and 

 bearing rather short blackish pubescence there, 

 but hollowed rather than inflated on the upper 

 part (fig. 95) and apparently bare ; vertex 

 shining black, long and narrow, extending 

 about half way towards the antennse and 

 leaving the eyes touching for about ten facets ; 

 proboscis brownish yellow. Eyes practically 

 bare ; facets on the larger upper part of the 



disc larger than those near where the eyes ^ ^./ -s-iz- ^ 



touch, and distinctly larger than those on the ig- -j-— "'^^^'^g" cmais 6. 

 lower part. Antennse dull brownish, rather 



yellowish brown on the two basal joints, but usually more or less darkened 

 or even blackened at the tip of the third joint ; basal joints with only minute 

 pale bristles beneath ; arista yellowish, long, and thin except at the base. 



Thorax and scutellum moderately shining black, but rather dulled by 

 the dense and coarse punctuation ; pubescence dense but most exceedingly 

 minute and depressed backwards ; mesopleuree polished purplish black on 

 their_ middle. Scutellum long, and with a distinct transverse furrow before 

 the tip. 



Abdomen shining black, but a little dulled by the veiy dense rather coarse 

 punctuation, while from every puncture a tiny short black or grey decumbent 



