ACKOCERA. 45 



Genus I. ACROCERA. 



ACROCERA, Mg. ; Illig. mag. (1806) ; LI. ; Mq. ; Ztt. Syrphm p., Pz. 

 Henops p., Fin. 



Corpus minoris magnitudiuis, subglobosum, gibbum, breviter pubescens. 



Color nigricans. Oculi nudi, obscure fusci, unicolores. Antennae 



prope verticem insert*. Alee vena tertia longitudinal! furcata. 



Body small, gibbous, almost globose, downy. Head small, oval, 

 contracted in front. Eyes bare, almost contiguous. Ocelli 3, on the 

 crown. Proboscis concealed. Antennas small, upright, 3-jointed, 

 seated near the crown ; first joint patelliform ; second cyathiform ; third 

 long, setiform. Thorax almost round, gibbous, much broader than the 

 head. Wings lanceolate, diverging, oblique, bare ; third longitudinal 

 vein forked. Alulae large, convex, hiding the little halteres. Abdomen 

 round, broader and thicker than the thorax, with 5 segments. Legs 

 delicate ; metatarsus as long as the other four joints. 



The Acrocerae are very sluggish, and are often seated in groups 

 on the withered trunks and branches of oak and other trees, about 

 which they fly when the sun shines in warm weather ; they also 

 frequent thickets and herbage beneath trees. 



1. globulus, Pz. ! fn. xxxvi. 20; LI.; Fin.; Mg.; Mq. ; Ztt. 

 Nigra, thoracis lateribus navo-maculatis et fasciatis, alis limpidis, abdo- 

 minefulvo apice flavo-fasciato, pedibus fulvis. Long. If; alar. 5 lin. 



Black. Head clothed with hoary hairs. Thorax clothed with very 

 short yellow hairs ; a pale yellow spot on each side of the fore border, 

 and a short oblique pale yellow band at the base of each wing. Wings 

 and alulae colourless ; veins and halteres yellow. Abdomen tawny ; an 

 irregular pale yellow band near the tip. Legs tawny ; ungues black. 



Appears during the summer, and frequents the withered 

 branches of the alder, the ash, the aspen, and other trees, (E.) 



2. albipes, Mg. zw. iii. 96. 4 (1822). globulus var., Fin.; Ztt. 

 Nigra, antennis fulvis apice nigris, thoracis lateribus navo-maculatis et 

 fasciatis, scutello flavo, alis limpidis, abdomine luteo basi nigro-fasciato 

 lateribus nigro-maculato, pedibus flavis. Long. 1| 2 ; alar. 4-5 lin. 



Black. Head and thorax clothed with pale, very short, yellow hairs. 

 Antennae tawny, black towards the tips. Thorax with a pale yellow 

 spot on each side of the fore border, and with a short oblique pale yellow 

 band at the base of each wing ; scutellum pale yellow. Wings and 

 alulae colourless; veins and halteres yellow. Abdomen luteous ; a black 

 band at the base, and on each side a row of black spots, which successively 

 decrease towards the tip. Legs yellow ; tips of the tarsi black. 



May be a variety of the preceding species. (E.) 



