[Reprinted from InsecutorInecitie Menstruus.Vol. ilU, Nor. 1-3, 1925]

AN UNDESCRIBED SPECIES OF' TANYDERUS
FROM WESTERN AUSTRALIA( Dipt ero, T anyil eiilae )Bv CHARLES P. ALEXANDER
Since the appearance of the paper by the writer on theAustralasian species of. Ta.nyderas (Ins. fns. Mens., 12, 141743, 1924), an undescribed species from western Australia has
been received from Dr. Eustace W. Ferguson. I am greatly
obliged to Dr. Ferguson for the privilege of examining thisfly, the type of which has been returned to him for inclusion
in one of the Australian museums.
Tanyderus(Radinoderus)

Female.-Length,

occidentalis, ne,ut'species'

aboui 24 mm.; wing, 19 mm.

INSECUTOR INSCITI.E

MENSTRUUS

33

Most closely allied to Z. (R.) terrae-reginae Alexander(Queensland), differing as follows :Vertex betrveenthe eyes extremely reduced.
Pronotum dark. Mesonotal praescutum largely brownish
black, the broad median stripe con{luent anteriorly rvith thedark lateral margins, restricting the obscure yellow groundcolor to posterior areas on the praescuturn which cross thcsuture onto the anterior half of the scutal region; posterior
scutum with a conspicuousbrorvnish black saddle that crosses
the notum l:etween the rvings; scutellum obscure brownish yellow, narrowly margined posteriorly with dark brorvn; postnotum dark brown. Propleura dark brown. Mesopleura darkbrown with a conspicuous pale yellow area beneath the wingroot that extends from just beneath the wing across the anterior
margin of the pteropleurite, inciuding most of the sternopleurite, thence passing onto the micldle coxae. Halteres vellow, the knobs dark brorvn. Legs with the middle coxae paleon outer face, as described above; femora yellow, the tips
broadly ancl conspicuously blackened; what appears to be thefore femur (legs largely detached) has a ver-v broad and conspicuous black ring near midlength, this occupying more than
one-third the entire segment; on what seems to be the middle
legs, this area is somewhat infuscated, being followed by abright yellow subterminal ring; tibiae yellorv with the bases
conspicuously and broadly blackened; tarsi obscure yellow.
Wings relatively narrow, the tips subfalcate; membrane whitish
subhyalinewith a relatively narrow and restricted uniform brownpattern, the distal third with a distinct X-shaped mark, the inner
cephalic portion of the mark occupying the tip of veins Sc1and Sc2 and here confluent with an inner Y-shaped marking
as in terrae-reg'i,nae,the stem and outer arm of the Y being along
the cord; two smaller costal areas close to the wing-base; nodark spot at tip of R1 ; veins in the darkened areas dark brownish black, not brownish yellow as in terrae regi,nae. Venation:
Veins Rr, R2 and Rs elongate and deflected strongly caudad
toward the wing-tip.

34

INSECUTOR INSCITITEMENSTRUUS

Abdomen dark brown, each tergite with a conspicuous elongate oval pale yellow marking, narrower basally, more dilated
distally, these areas approximated on the midline of the dorsum; sternities dark brown with three conspicuous yellow
rnarkings, the two laterals lying parallel, broader behind, theiranterior ends extended into a point; the median area is diamond-shaped and lies a little more caudad than the other markings; these triple sternal markings reach their best developmenton the intermediate sternites, the lateral areas subobsoleteon
the basal sternites, the median area becoming reduced and deformed on the outer sternites; genital segment dark brown.
H abitat.-Western Australia.
Holotype, t, Swan River (J. Clark).
Type returned to Dr. Ferguson.