Sept., '04] ENTOMOLOGICAL NEWS. 247 



A new Species of Psolodesmus (order Odonata) 



from Formosa. 

 BY E. B. WILLIAMSON. 



Among some Odonates recently received from Rev. H. 

 Loomis are specimens from Formosa of a large and beautiful 

 species of Psolodesmus, of the subfamily Calopteryginse, which 

 seems to be new. 



The genus Psolodesmus may be recognized as belonging to 

 de Selys' Legion Calopteryx (exclusive of Vestalis} by the 

 following characters : antenodals of the first and second series 

 present, numerous, largely coinciding excepting possibly a few 

 near the nodus ; M t -\- 2 rising abruptly upward from M 3 ; 

 wings scarcely or not at all petioled ; subquadrangle straight, 

 not bent at the level of the arculus ; basal space about equal 

 to or shorter than the quadrangle ; and a posterior branch 

 of Cu 2 present. Psolodesmus is related to Mnais by the pres- 

 ence of a true stigma in both sexes ; basal space free ; arculus 

 bent ; M : + 2 fused with the radius for a short distance ; sect- 

 ors not branched ; posterior branch of Cu 2 not directed 

 basally. From Mnais, Psolodesmus is distinguished by the 

 more retracted nodus (in Mnais the distance to the nodus 

 from the wing base is more than two-fifths the wing length, 

 in Psolodesmus less than two-fifths the wing length, and in 

 Psolodesmus in the front wings M 2 arises several cells beyond 

 the subnodus, and not at the subnodus as in Mnais^) ; by the 

 more complex venation (secondary sectors and cross- veins 

 more numerous in Psolodesmus than in Mnais) ; by the long 

 and narrow, quadrangle (in Mnais the quadrangle is scarcely 

 as long as the basal space, in Psolodesmus it is about i% times 

 as long, and with about twice as many cross- veins as in Mnais} ; 

 by the medio-anal link (i. c. , the vein closing the distal end of 

 the quadrangle and subquadrangle) of the hind wings at right 

 angles to the long axis of the wing or with the anterior end 

 slightly more basal than the posterior end (in Mnais the pos- 

 terior end of the medio-anal link is decidedly more basal than 

 the anterior end) ; and by the hind margin of the wings, 

 especially the hind wings, behind the subquadrangle, decidedly 

 more concave. 



