OCCASIONAL PAPERS

OF THE

CALIFORNIA ACADEMY OF SCIENCES

No. 39, 24 pages, 9 figures, 1 plate July 10, 1963-

THE GENUS CALOTARSA,

WITH SPECIAL REFERENCE TO

C INSIGNIS ALDRICH

(DIPTERA: PLATYPEZIDAE ) *

By
Edward L. Kessel

University of San Francisco
and
California Academy of Sciences

Introduction

The flat-footed flies, constituting the family Platypezidae, are of par-
ticular interest because of the character which gives these insects both their
common and family names. This character consists of the flattened segments
of the posterior tarsi as found in the species of certain of the genera, viz.,
Clythia Meigen {-Platypeza }Aeigen), Protoclyt hia Kessel, Metaclythia Kessel,
and Calotarsa Townsend. But of these, Calotarsa is unique in the possession
of pronounced ornamentation of these hind tarsi in the males (figs. 1, 3, 9).

The genus Calotarsa includes only three known species, all of which
are confined to North America: Calotarsa pallipes (Loew) from the eastern
area of the continent; Calotarsa c^/cea/o (Snow), known only from one locality
in New Mexico; and Calotarsa insignis Aldrich from western North America.

The calotarsas are the largest paltypezids known, specimens occasion-
ally attaining a length of 10 mm. in the male and 8 mm. in the female. On the
other hand, individuals half these dimensions are often encountered, these

Based on studies aided hy National Science P'oundation grant G 19006.

2 CALIFORNIA ACADEMY OF SCIENCES (Occ. Papers

smaller flies no doubt coming from larvae which were denied maximum growth
by a shortage of food.

To my knowledge, no information regarding the host fungi of these flies
has been published previously. The larvae have been mentioned in only one
paper (Kessel, 1961). As for the mating activities of calotarsas, Snow (1894)
gave some clues, and my wife and I (Kessel and Kessel, 1961, 1962a, 1962b)
have published comparative comments in connection with discussions con-
cerned primarily with platypezids belonging to other genera. Except for these
few references, practically nothing has appeared in the literature regarding the
biology of these flies.

The generic name Calotarsa was established by Townsend (1894a) for
the reception oihis Calotarsa ornatipes which he described in the same paper.
This species was based on a single specimen, a male collected at Champaign,
Illinois, which had been sent to him by S. A. Forbes. Townsend was so im-
pressed by the elaborately decorated hind tarsi of this specimen that both his
generic and specific names refer to this character (fig. 1). However, several
entomologists had difficulty in accepting these decorations as authentic ana-
tomical structures, and D. W. Coquillett, among the doubters, asked Townsend
in a letter if they could be of extraneous vegetable origin. In reply, Townsend
(1894b) admitted that he too had been tempted to regard these structures as
unnatural until he observed that the right and left sides correspond exactly.
Townsend (1894a) made a serious error in his initial placement of Calo-
tarsa, supposing it to be an anomalous member of the family Syrphidae. 3ut
his published figure of the wing venation and the text of his description were
sufficient for several entomologists to recognize that proper placement should
be in Platypezidae. Among these workers were D. W. Coquillett and J. M. Aid-
rich who wrote letters, and Williston (1894) and Banks (1894). Banks also an-
nounced that he had a specimen of this same fly which he had collected in
Ithaca, New York, several years before. Thus it was established that Town-
send had named a good species, not a "freak" specimen.

It was ultimately discovered, however, that although Townsend had
named a good species, the name which he gave it was a synonym. It was John-
son (1908) who concluded from circumstantial evidence that what Townsend
had described as C. ornatipes was in reality the male of a species which
Loew (1865) had named Platypeza pallipes and described from a female col-
lected by Osten Sacken in the District of Columbia. Johnson had suspected

Pl.ATK 1

Upper figure. Male of C. insignis in full light.

Lower figure. Male of C insignis in dark surroundings. Note the reflections of the
flags which are attache".! tothe posterior tarsi . Kodachromes by author.

OCC PAPERS CALIF. ACAD. SCI., NO. 39

(KESSEL) PLATE 1

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No. 39) KESSKL: THK GHNUS CAI^OTARSA 3

the synonymy as early at 1897 when on North Mountain (above StuU), Penn-
sylvania, he "captured almost in the same swing of the net" both (1. ornatipes
and P. pallipes. Similarly, Owen Bryant, on September 5, 1903, collected a
number of both of these supposed species five miles east of the Isles of Shoals
in New Hampshire. Also, Johnson collected six specimens of P. pallipes on
a window in Boston between September 24 and 28, 1903, and three days later
he found a dead specimen of C. ornatipes at the same place. Thus it was es-
tablished that P. pallipes with no males and C. ornatipes with no females con-
stituted one species, and on the basis of priority the latter trivial name be-
came a synonym of the former. As for the proper generic designation, I prefer
to follow Townsend and Aldrich in accepting Calotarsa as the proper generic
name for this and the other two species which are treated in this paper.

Acknowledgments

Acknowledgments of assistance in the preparation of a paper of this
type must be made to many persons and institutions. Chief among the latter
are: Museum of Comparative Zoology, Harvard; Snow Museum, University of
Kansas; Canadian National Collections, Ottawa; Oregon State University; Uni-
ted States National Museum; California Insect Survey Collection, University
of California, Berkeley; Carnegie Museum, Pittsburgh. Individuals, who in one
way or another, have provided specimens for study include: T. G. H. Aitken,
P. H. Arnaud, Bruce Barichievich, W.R.Bauer, J. Bedingfield, G. E.Bohart,
R. M. Bohart, I. Branson, D. W. Breedlove, G. W. Byers, LeroyChilds, Frank
Cole, E.J.Coher, C. H. Curran, J. P. Darlington, R.C.Dickson, R. R. Dreis-
bach, T. H. Farr, K. M. Fender, J.Hansen, P. D. Hurd, Dean Jamieson, Peter
Keyes, Jean Laffoon, J. D. Lattin, G. Lindquist, A. L. Melander, R. T. Orr,

E. S. Ross, C. W. Sabrosky, G. E. Shewell, H. W. Smith, Alan Stone, A. H. Stur-
tevant, K. A. Trexler, W.H.Tyson, G.E.Wallace, J.L. Way, M.R.Wheeler,

F. X. Williams, W. W. Wirth, P. W. Wygodzinsky. Berta B. Kessel, my wife, has
assisted me throughout the field work, and many of the flies which bear my
collector's label were in reality collected by her.

Permission to collect platypezids for specified limited periods and with-
in park boundaries was obtained from the authorities at Yosemite and Sequoia
National Parks. The California State Division of Beaches and Parks has pro-
vided me with year-round collecting permits for the past several years, cover-
ing all State parks and monuments. These were obtained through the kindness
of John H. Michael and Burgess W. Heacox, and made possible the collection
of much of the material considered in this paper.

I also wish to acknowledge the contributions of those who have helped
with the preparation of the paper in special ways: Bernardine B. Engstrom
transposed data from labels and typed the manuscript; David Kuty made the
wing prints; George E. Johnson made the drawings of the male tarsi of the
three Calotarsa species; Maurice Giles did the photographic preparation for

4 CALIFORNIA ACADEMY OF SCIENCES ' (Occ. Papers

the illustrations; and finally, Dr. and Mrs. G Dallas Hanna produced the color
plate of Calotarsa insigtiis.

Generic Relationships

It seems certain that of known genera, Calotarsa is most closely re-
lated to Clythia (-Platypeza). The larvae of Calotarsa insignis ate essential-
ly like those of Clythia agarici. The wing venation (figs. 2, 4, 8) is very sim-
ilar to that found in Clythia and Protoclythia. Because of the specialized na-
ture of the posterior tarsi of the males (figs. 1, 3, 9) in Calotarsa, we must
look to the females (fig. 7) in comparing these structures in Calotarsa with
those of other genera. In this respect, Calotarsa is similar to Metaclythia and
Clythia. From these observations we may conclude that Calotarsa, like Meta-
clythia, stemmed from a Clythia-like stock.

Distinguishing the Species

Except for the ornamentation of their posterior tarsi, the males of the
three species are very similar in appearance. Negative wing prints, obtained
by placing the wing itself in the enlarger and printing from it in place of the
usual photographic film, are accurate reproductions of the venation. Such prints,
representing the males of the three species, reveal no important differences.
In all three species, the posterior branch of the fourth longitudinal vein is
clearly short of the wing margin, and the posterior cross vein is separated
from the wing margin by a distance which is less than its own length. The
most striking difference in the venation of these species is the noticeably
shorter posterior branch of the fourth vein in C. calceata (fig. 4). In most
specimens it extends barely one-third of the distance from the point of branch-
ing of the fourth vein to the wing margin. In C. pallipes (fig. 2) and C. ins ig-
nis (fig. 8), it extends about half of the distance to the wing border. But these
typical dimensions are sometimes modified in individuals and to the degree
that the distinctions are not clear-cut and so become untrustworthy. The dis-
tance that the posterior cross vein is removed from the wing margin is an even
more variable character within each species, and therefore of even less value.

The species are easily separated in the males, however, by an examin-
ation of the posterior tarsi. While all three species have the fifth segment nor-
mal, all have the other four segments modified in some important manner. Even
C. pallipes (fig. 1), which at first glance seems to bear no appendage on the
second segment like the others, often shows a rudimentary process which may
be regarded as an atrophied filament which once was similar in structure to
that which now adorns the first segment. This suggests that the basic Calo-
tarsa stock from which our three known and present-day species are descend-
ed, had a prominent ornamental appendage on each of the first four segments
of the tarsus in the male. Presumably these segments are serially homologous,
and the primitive or basic-type form of ornament on each was something like

No. 39) KESSEL: THE GENUS CALOTARSA 5

we now find on the second segment of C. calceata (fig. 3) or on the fourth seg-
ment of C. itisignis (fig, 9). Possibly the hoof-like appendage of this fourth
segment in (,. itisignis is the more primitive with its maximum development,
and the second-segment structure of C. calceata is a modification of this plan
by reduction and differentiation.

At any rate, one may infer that such structures were derived from the
setaceous appendages which are found on the first segment of C. calceata,
the first segment and the second as well in C pal I i pes (if the rudiment men-
tioned above is counted), and the first and second segments of C. itisignis.
Each of these has a flattened wing-like base, and each of them except the rud-
imentary one, has a terminally expanded portion. The more generalized orna-
ment of the second segment of C. calceata could also, by reduction, have pro-
duced the silver and black flags which occur on the third segments of the pos-
terior tarsi of the males of C. pallipes and C. insignis, and from which the
latter species gets its name. It must be rem.embered that all of these hind-tar-
sal ornaments of male calotarsas are flat and very thin. The one on the sec-
ond segment of C calceata, although essentially black, possesses numerous
semitransparent spots, several of which are quite large. These could have
been enlarged still more and fused to produce the silvery flags with black
markings of C. insignis and C. pallipes.

The secondary filament which is attached to the margin of the flag of
C. pallipes is of particular interest. When Townsend (1894a) described the
male of this species as his C. ornatipes, he placed and figured this filament-
ous tassel so that it originates from the proximal margin of the flag. Later
(Townsend, 1894b), he commented about receiving from J. M. Aldrich a drawing
of the hind tarsus of a male calotarsa which he believed to represent a spe-
cies similar to but distinct from C. ornatipes. This had been captured at Brook-
ings, South Dakota. The principal difference of the proposed new species, as
shown by the drawing which Aldrich had made, was that the filamentous ap-
pendage was attached to the distal margin of the flag instead of the proximal
margin. Townsend proposed that Aldrich describe his fly as a new species.
Instead, he sent his drawing to W. A. Snow, who was then specializing on Plat-
ypezidae, and asked for his opinion. The type of C. ornatipes was deposited
in the Snow Museum (named for Snow's father) at the University of Kansas,
so was close at hand for Snow to compare with the drawing he had received

from Aldrich. Snow (1895) concluded, "lean see no specific , differences

The membranous appendage on the third tarsal joint is on the same side of
the leg in both specimens." The only trouble with this decision is that in
all of the specimens of C. pallipes which I have examined, I have found this
filamentous appendage attached to the distal margin of the flag (fig. 1), not
the proximal edge as shown in the drawings of Townsend (1894a, fig. 5), Snow
(1894a, fig. 2), and even Aldrich (1906, fig. 2). It is strange that all of these
men made the same error, especially Aldrich, because he had already figured

CALIFORNIA ACADEMY OF SCIENCES

(Occ. Papers

it correctly for his South Dakota specimen.

While it is easy to separate the males of the species of Calotarsa by
means of the ornamentation of their posterior tarsi, one must depend on less
obvious characters to distinguish the species in the case of female specimens.
Nevertheless, the identifications maybe made with a high degree of certainty.
In the females of C. ws ignis the abdomen is all yellow above, with, at most,
thin, transverse, darker-yellow bands across the posterior margins of some
segments. By contrast, the females of C. pallipes and C. calceata have the
abdomen ash colored above, and with obvious transverse bands of black to
brown across segments 2 to 5. In both species these bands are gradually
widened toward the middle so that they become triangular and pointed toward
the front. In C. c<z/ce^/fl this widening is sufficient to bring the apexes of the
triangles to about the anterior margins of their respective segments. In C.
pallipes this widening is less pronounced so that the apexes of the triangles
are clearly short of the anterior margins of their segments.

The Species
Calotarsa pallipes (Loew).

(.Figures 1, 2.)

Platypeza pallipes LoEW (1865, p. 81); Aldrich (1905, p. 342); Johnson (1908, p. 58).
Calotarsa omatipes Townsend (1894a, pp. 52, 102); Aldrich (1906, p. 123).
Platypeza omatipes. Banks (1894, p. 88); Williston (1894, p. 116); Snow (1894, p. 143;
1895, p. 207); Johnson (1897, p. 254; 1904, p. 19); Greene (1908, p. 241).

Geographical Distribution. This species is known to range from Que-
bec, south to North Carolina, and west to South Dakota. Previously published

Figure 1. Posterior tarsus of the male of C. pallipes.

^

No. 39)

KESSEL: THE GENUS CALOTARSA

records gave the District of Columbia, Illinois, New York, Pennsylvania, Mas-
sachusetts, New Hampshire, and South Dakota. This list is now more than
doubled in number as nine states and provinces have been added as follows:
Quebec, Ontario, Maine, Vermont, Connecticut, Michigan, Minnesota, Iowa, and
North Carolina.

Material examined. In the following list of specimens which I have ex-
amined during this study, the initials (H.K.) are used to designate the many
flies which bear labels listing Hugo Kahl as the collector. He collected more
platypezids of this and other species in eastern United States than any other
person, and most of the flies listed here as coming from Pennsylvania were
taken by him. The names of the other collectors mentioned in the list are giv-
en in full.

Figure 2. Wing of the male of C. pallipes. This print, as well as those shown
in figures 4 and 8, was made directly from the wing, mounted on a slide and placed in
the enlarger.

CONNECTICUT: Storrs: IX-16-53 (H.W.Smith), 2 males, 2 females; X-
4-53 (H.W.Smith), 5 females; X-17-53 (H.W.Smith), 4 females.

IOWA: Ledges State Park, Boone County: IX-6-50 (J. Laffoon), 2 females;
X-13-50 0- Laffoon), 1 male.

MAINE: Nixon: VIII-31-53 (E. L. Kessel), 1 female.

MASSACHUSETTS: Amherst: XI-2-43 (H. Fernald), 1 female. Let^ere//;
IX-12-56 (T.H.Farr), 5 males; IX-22-52 (E.J.Coher), 4 females. Woods Hole:
IX-19-23 (A.H.Sturtevant), 1 male.

MICHIGAN: Chippewa County: no date (R.R.Dreisback), 1 male. Goge-
bic County: VIII-25-47 (R.R.Dreisbach), 1 female.

8 CALIFORNIA ACADEMY OF SCIENCES (Occ. Papers

MINNESOTA: 5 miles 5. of Pequot Lakes: IX-30-48 (Hicks and J.Laf-
foon), 1 female.

NEW YORK: Nyack: VII-2-84 (no collector), 1 male. Romapo: IX-17-10
(no collector), 1 male. Woodw. Lake: IX-4-10 (no collector), 1 male.

NEW HAMPSHIRE: Dolly Copp Camp, White Mountains: IX-4-40 (J.Han-
sen), 1 male. Franconia: No date (Mrs. A. T. Slosson), 3 females. Isles of
Shoals: No date (Owen Bryant), 1 male, 1 female. Kings Ravine, Mt. Adams,
White Mountains: X-12-40 (J. Hansen), 1 female.

PENNSYLVANIA: North Mountain: VIII-28-97 (C.W.Johnson), 1 female;
IX-1-97 (C.W.Johnson), I female; IX-2-97 (C.W.Johnson), 1 male. Pittsburgh:
IX-4-08 (H.K.), 1 male; IX-5-13 (H.K.), 1 male; IX-9-13 (H.K.), 1 male; IX-9-
08 (H.K.), 1 male; IX-9-11 (H.K.), 1 female; IX-10-08 (H.K.), 1 male; IX-10-14
(H.K.), 1 female; IX-11-08 (H.K.), 2 females; IX-12-09 (H.K.), 1 male; IX-14-

08 (H.K.), 2 females; IX-15-08 (H.K.), 6 females; IX-16-08 (H.K.), 2 females;
IX-17-08 (H.K.), 16 females; IX-18-07 (H.K.), 1 female; IX-19-08 (H.K.), 8 fe-
males; IX-19-14 (H.K.), 2 males, 1 female; IX-20-08 (H.K.), 2 females; IX-20-

09 (H.K.), 1 female; IX-20-13 (H.K.). 1 female; IX-20-14 (H.K.), I male; IX-
21-08 (H.K.), 12 females; IX-21-10(H.K.), 1 female; IX-22-08 (H.K.), 1 female;
IX-22-10 (H.K.), 2 males; IX-23-07 (H.K.), 2 males; IX-23-08 (H.K.). 9 males,
4 females; IX-23-10 (H.K.), 1 male, 1 female; IX-23-14 (H.K.), 2 females; IX-
24-13 (H.K.), 1 male, 1 female; IX-25-08(H.K.), 1 male; IX-25-13 (H.K.), 1 fe-
male; IX-25-14(H.K.), 2 females; IX-26-09 (H.K.), 2 males, 1 female; IX-27-13
(H.K.), 1 male; IX-28-11 (H.K.), 1 female; IX-28-13 (H.K.), 6 males; IX-28-14
(H.K.), 1 female; IX-29-07 (H.K.), 1 male; IX-29-14 (H.K.), 4 females; X-1-03
(H.K.), 1 female; X-1-10 (H.K.),1 male; X-1-14(H.K.), 1 female; X-2-07 (H.K.),

1 female; X-2-13 (H.K.), 2 females; X-2-14 (H.K.), 1 female; X-3-13 (H.K.), 2
females; X-3-14 (H.K.),6 males, 5 females; X-4-08 (H.K.), 4 females; X-4-11
(H.K.), 1 male; X-4-13 (H.K.), 1 female; X-5-11 (H.K.), 1 male; X-5-14 (H.K.),

2 females; X-8-14 (H.K.), 1 female; X-10-09 (H.K.),2 females; X-12-14 (H.K.),
2 females; X-26-14 (H.K.), 1 female; XI-13-12 (H.K.), 1 female.

ONTARIO: Jordan: IX-7-19 (C.H.Curran), 1 male. Ottawa: X-5-23 (C.H.
Curran), 3 females; X-12-45 (J. Bedingfield), 1 female.

QUEBEC: Abbots ford: VIII-30-36 (G.E.Shewell), 2 females; IX-2-36(G.
E.Shewell), 1 male. Mt. Orford: IX-9-37 (G.E.Shewell), 2 females. St.Annes:
VIII-5-38 (no collector), 1 male.

VERMONT: Balboa Mountain: IX-10-22 (no collector), 1 female. Rolton
Mountain: IX- 1-22 (O.Bryant), 3 males.

No. 39) KESSEL: THE GENUS CALOTARSA 9

Seasonal distribution. The earliest record for this species is for Nyack,
New York, July 2, 1 male. I am inclined to doubt this date, but because no
collector was given, it is impossible to check on it. The next earliest record,
also for a male, is for August 5, from St. Annes, Quebec. The earliest record
for a female is August 25, from Gogebic County, Michigan. It has been my ex-
perience with C. insignis, and numerous other platypezids, that the males be-
gin to appear at the beginning of the season with some females, but not seven
weeks in advance of them as the first record would suggest. In general, the
season for platypezids in our Northern Hemisphere begins in the north and
progresses southward. If the July 2 date were for a fly taken in Ontario or
Quebec, I would be more inclined to accept it. I suspect that an error of a
month is involved, particularly in view of the fact that the earliest female,
taken on August 25, is from the northern state of Michigan. While more col-
lecting is needed to make certain, I believe the season for C. pallipes begins
in early August, not July.

The latest date that I know of for the collection of a male of this spe-
cies is October 5. This record is from Pittsburgh, Pennsylvania. The latest
date for a female, also from Pittsburgh, is November 13. We may conclude,
therefore, that the season for the adults of C pallipes is from early August
to middle November, the males disappearing by the middle of October.

Fungus hosts. I know of no data which indicate what fungi the larvae
of this species use for food. To my knowledge, the immature stages have not
been observed.

Mating habits. These seem to be unknown for C. pallipes, but it is pre-
sumed that they are similar to those of the other two species of the genus
which are discussed below.

Calotarsa calceata (Snow).

(Figures 3, 4.)

Platypeza calceata Snow (1894, pp. 146-148).

Calotarsa calceata, Aldrich (1905, p.341; 1906, pp. 123-124); Kessel and Kessel (1961,
p. 295; 1962a, p. 57; 1962b, p. 290).

This species is known only from the type series of 75 males and 1 fe-
male, all taken at Hop Canyon, Magdalena Mountains, Socorro County, New
Mexico. These flies were captured by W. A. Snow, August 19-21, 1894. In an
attempt to obtain more of them, my wife and I visited this locality on August
19, 1951 (Kessel, 1952), but were unsuccessful.

Snow's observations on C. calceata were particularly significant, for he
seems to have been the first to describe the swarming of males among platy-
pezids. This phenomenon, and the mating activities which are related to it,

10

CALIFORNIA ACADEMY OF SCIENCES

(Occ. Papers

will be considered in some detail under the next species, C. insignis.

Snow learned nothing of the food plants and immature stages of his spe-
cies.

'^'^s.

t

Figure 3- Posterior tarsus of the male of C calceata.

Figure 4. Vt'ing of the male of C calceata.

Calotarsa insignis Aldrich.
(Figures 5, 6, 7, 8, 9, and plate 1.)

Calotarsa insignis Aldrich (1906, p. 126); Kessei. (1961, p. 9); Kessel and Kessel
(1961, p. 296; 1962a, pp. 60, 61, 64; 1962b, p. 289).

No. 39)

KESSEL: THE GENUS CALOTARSA

11

Geographicai, distribution. Calotarsa insignis is known from southern
British Columbia (Vancouver Island and Cultus Lake), western Oregon, much
of California, and a single record from western Montana. Presumably it also
occurs in Washington, Idaho, and perhaps southern Alberta, but I have looked
in vain for it in each of these areas. Likewise, A. L. Melander, who was well
acquainted with platypezids and collected them at every opportunity, did not
collect C. insignis in Washington and Idaho, although he was located at Wash-
ington State College for some time and did much collecting in both of these
states. Similarly, J. M. Aldrich, who named this species and certainly would
not overlook it, was a member of the faculty at the University of Idaho and
did much collecting in the area, but did not find it. There is no question, how-
ever, about the Montana record. I captured the fly (a male) myself, 9 miles
east of Paradise, Sanders County, August 31, 1962.

Figure 5- Dorsal view of the male of C insignis.

Material examined. In the following list of specimens which I have ex-
amined during this study, I have used my initials (E.L.K.) to designate those
flies which bear labels listing E.L.Kessel as the collector. Actually, much of
this material was collected by Berta B. Kessel, my wife, who has been my
constant companion in the field work. The names of the other collectors are
given in full.

Figure 6. Ventral view of the male of C insignis.

12 CALIFORNIA ACADEMY OF SCIENCES (Occ. Papers

BRITISH COLUMBIA: Cultus Lake Provincial Camp: X-19-38 (J.K.
Jacob); 1 male. Golds tream Privincial Camp, Vancouver Island: X-16-61 (E.L.
K.), 3 females; X-17-61 (E.L.K,), 3 females. Miracle Beach Provincial Park,
Vancouver Island: X-14-61 (E.L.K.), 1 female. Stamp Falls Provincial Park,
Vancouver Island: X-13-61 (E.L.K. ), 2 females. Victoria: X-16-61 (E.L.K.),
1 female.

CALIFORNIA: Alameda County: Berkeley: X-31-47(W.W.Wirth), 5 males;
XI-9-36 (E.I.Schlinger), 1 female; XI-20-38 (T.G.H. Aitken), 34 females; XI-
no day-36 (T.G.H. Aitken), 1 female; Xl-no day-36 (G. E. Bohart and R.M. Bo-
hart), 3 females; XII-4-36 (R.C.Dickson), 1 female; XII-9-36 (R.C. Dickson),

1 female. Niles: 1-4-62 (W.H.Tyson), larvae. Oakland: XI-8-57 (B.Barichie-
vich), 2 females; XI-10-57 (B.Barichievich), 1 female; XI-23-57 (B.Barichie-
vich), 2 females. AmadorCovnty: 4 miles E. of Volcano: X-2-60 (E.L.K.), 9
males, 3 females. Butte County: Curry-Bidwell State Park: XI-20-62 (E.L.K.),

2 females. Contra Costa County: D^wz^/Z/e; 1-7-52 (F.X.Williams), 11 female,
No locality: X-29-36 (G.E. Bohart), 1 male. Del Norte County: Klamath: X-30-
61 (E.L.K.), 1 female. Patrick Creek: XI-11-61 (E.L.K.), 3 females; XI-14-59
(E.L.K.), 5 females. Glenn County: 2 miles N. of Red Bridge: XI-19-60 (E.L.
K.), 18 females. Humboldt County: Grizzly Creek Redwoods State Park: lX-23-
60 (E.L.K.), 2 males; XI-5-60 (E.L.K.), 19 females; XI-8-59), (E.L.K.), 10 fe-
males. Myers Flat: XI-1-59 (E.L.K.), 5 females. Orleans: X-25-59 (E.L.K.),
5 females. Prairie Creek State Park: XI-4-60 (E.L.K.), 3 females. Van Duzen
Forest Campground: XI-7-59 (E.L.K.), 1 male, 9 females. Willow Creek (East
Ford) Forest Campground: X-25-59 (E.L.K.), 8 females; X-31-59 (E.L.K.), 3
females. Kern County: Kern River (15 miles S. Miracle Springs): XII-2-60 (E.
L.K.), 13 females. Kernville: XII-3-60 (E.L.K.), 1 female. Lake County: Adams
Springs: IX-22-59 (E.L.K.), 1 male. Anderson Springs; IX-30-50 (W.R.Bauer),
1 male; XI-22-59 (E.L.K.), 5 females. Los Angeles County: Arcadia: X-15-49
(M.R.Wheeler), 7 females; XI-18-49 (M.R.Wheeler), 1 female. Glendale: XI-24-
62 (E.I.Schlinger), 5 females; XI-25-50 (E.I.Schlinger), 1 female; XII-21-50
(E.I.Schlinger), 2 females. Pasadena: XI-16-49 (M.R.Wheeler), 2 females; XI-
21-49 (M.R.Wheeler); 1 female; XI-25-49 (M.R.Wheeler), 1 female. South Pasa-
dena: XI-8-55 (J.L.Way), 1 male. V/est Ford, San Gabriel Canyon: XI-18-49, 1
female. Madera County: Westfall Ranger Station: X-16-60 (E.L.K.), 1 female.
Marin County: Mill Valley: 1-12-46 (E.L.K.), 3 females; 1-19-46 (E.L.K.), 2
females; IX-22-46 (E.L.K.), 2 males; IX-22-51 (E.S.Ross); 1 male; X-4-45 (E.
L.K.), 1 male; X-7-45 (E.L.K.), 3 females; X-7-48 (E.L.K.), 4 males, 7 females;
X-12-47 (E.L.K.), 2 males, 1 female; X-16-47 (E.L.K.), 3 males, 7 females;
X-18-47 (E.L.K.), 10 males, 67 females; X-20-45 (E.L.K.), 3 females; X-21-45

(E.L.K.), 43 females; X-21-48 (E.L.K.), 2 males, 1 female; X-24-45 (E.L.K.),
14 males, 21 females; X-25-47 (E.L.K.), 2 males, 29 females; X-26-47 (E.L.K.),
1 female; XI-1-45 (E.L.K.), 65 females; XI-9-47 (E.L.K.), 1 male, 30 females;

No. 39) KESSEL: THE GENUS CALOTARSA 13

XI-20-47 (E.L.K.), 1 female; X-21-45 (E.L.K.), 13 males, 6 females; XI-27-47
(E.L.K.), 8 males, 5 females; XII-29-45 (E.L.K.), 3 females. Navato: X-24-51
(E.L.K.), 17 males; XI-21-48 (E.L.K.), 1 male, 1 female. Mariposa County:
Wowona Campground, Yosemite National Park, X-22-60 (E.L.K.), 3 females.
Yosemite Valley, Yosemite National Park: X-15-60 (E.L.K.), 2 males, 10 fe-
males; X-22-60 (E.L.K.), 1 male, 10 females. Mendocino County: 2 miles up
Navarro River: XII-5-59 (E.L.K.), larvae. Mouth of Pieta Creek: X-29-61 (E.L.
K.), 2 females; X-13-61 (E.L.K.), 6 females; XI-18-60 (E.L.K.), 14 females.

Figure 7. Female of C. insignis.

Standish Mickey State Park: X-29-61 (E.L.K.),2 females. 5 miles N. of Willets:
X-29-61 (E.L.K.), 1 female. Merced County: McConnell State Park: XI-16-60
(E.L.K.), larvae. Monterey County: Pfeiffer-Big Sur State Park: 1-3-60 (E.L.
K.), larvae; X-8-60 (E.L.K.), 2 males, 2 females; XI-28-59 (E.L.K.), 7 males,
16 females; XII-19-59 (E.L.K.), 17 females. Nacimiento Canyon Forest Camp-
ground: X-8-60 (E.L.K.), 2 males, 4 females. Plaskett Creek Forest Carjip-
gro«« J; XII-20-59 (E.L. K.), 2 females. Napa County: Bothe-Napa Valley State
Park: XI-8-62 (E.L.K.), 1 female, XI-16-62 (E.L.K.), 1 male, 3 females. Nev-
ada County: Nevada City: X-19-62 (E.L.K.), 2 females. Rough and Ready:
XII-28-60 (I.Branson), larvae. Washington: X-19-62 (E.L.K.), 3 females. White
Cloud Forest Campground: X-19-62 (E.L.K.), 1 female. Orange County: Low-
er San Juan Forest Campground: XI-16-61 (E.L.K.), 5 females; XII-29-59 (E.
L.K.), 1 female. Trabuco Forest Campground: XI-15-61 (E.L.K.), 10 females.
Plumas County: Greenville: IX-27- 59 (E.L.K.), 1 male; X-2-59 (E.L.K.), 1
male; X-9-59 (E.L.K.), 1 female. Riverside County: Vpper San Juan Foresrt
Campground: XU-6-61 (E.L.K.), larvae. San Benito County: San Juan Canyon:
X-10-60 (E.L.K.), larvae; XII-10-60 (E.L.K., larvae. San Bernardino County:
Mill Creek Forest Campground: XlI-27-60 (E.L.K.), 2 females. San Diego Coun-
ty: DeLuz: XII-7-61 (E.L.K.), 1 male, 12 females. Fallhrook: XII-7-61 (E.L.
K.), 1 female; XII-26-59 (E.L.K.), 4 females. SanLuis Rey Forest Campground
(near Lake Henshaw): XII-12-61 (E.L.K.), larvae. Pauma: XII-27-59 (E.L.K.),
2 females. San Francisco County: Golden Gate Park: X-12-47 (E.L.K.), 1
male, 1 female; X-14-57 (B. Barichievich), 1 male; X-17-47 (E.L.K.), 1 male;

14

CALIFORNIA ACADEMY OF SCIENCES

(Occ. Papers

X-17-62 (R.T.Orr), larvae; X-18-57 (B. Barichievich), 1 male; X-20-47 (E.L.
K.), 1 male, 2 females; X-24-59(E.L.K.), 1 female; X-30-57 (B. Barichievich),
4 males, 4 females; XI-1-47 (E.L.K.), 5 males, 3 females; XI-4-47 (E.L.K.),
2 males, 8 females; XI-4-57 (B. Barichievich), 1 male; XI-7-47 (E.L.K.), 1 male,
1 female; XI-8-57 (B. Barichievich), 1 female; XI-9-47 (E.L.K.), 1 male, 1 fe-
male; XI-11-47 (E.L.K.), 8 females; XI-11-57 (B. Barichievich), 2 males, 6 fe-
males; XI-14-47 (E.L.K.), 1 female; XI-15-57 (B. Barichievich), 3 females;
XI-26-47 (E.L.K.). 1 female; XI-27-61 (E.L.K.), 1 female; XII-1-47 (E.L.K.), 1
female; XII-3-47 (E.L.K.),1 female; XII-8-59 (E.L.K.), 1 male, 1 female; XII-
12-47 (E.L.K.)> 3 females; XII-29-47 (E.L.K.), 1 female. Verba Buena Island:
X-5-58 (G.Lirrdquist), 1 male. San Joaquin County: Caswell State Park: XI-24-
60 (E.L.K.), 12 females. San Luis-X)bispo County: Cerro Alto Forest Camp-
ground: XII-23-61(E.L.K.), 4 females. Marquart Park: XII-24-61 (E.L.K.), lie-
male. Routzahn Park: XII-23-61 (E.K.K.), 10 females. San Mateo County: Corte
de Madera Creek, Portola: XII-10-59 (Paul Arnaud), 55 males, 1 female. Par-
tola State Park: Xl-27 -59 (L.L.K.), 4 females. Santa Barbara County: Miguel-
ito Park: XII-22-61 (E.L.K.) 2 females. Paradise Park: XII-21-61 (E.L.K.), 3
females. Santa Barbara: XII-12-59 (D.E.Breedlove), 13 females; XII-15-59 (D.
E. Breedlove), 1 male, 7 females. Santa Rosa Park: XII-22-61 (E.L.K.), 1 fe-
male. Santa Clara County: Los Altos: IX-27-61 (Dean Jamieson), 1 male. fAt.
Madonna County Park: XII-18-59 (E.L.K.), 2 females. Stanford University: I-
no day-16 (Isabel McCracken), 2 males, 1 female; X-7-00 (J.M.Aldrich), 1 male
(type series); X-28-05 (J.M.Aldrich), lfemale(type series); X-28-07 (J.M.Ald-
rich), 1 female; XI-25-53 (Paul Arnaud), 1 female. Santa Cruz County: Big
Basin Redwoods State Park: XII-12-59 (E.L.K.), 6 females, larvae. Wildwood

Figure 8. Wing of the male of C. insignis.

No. 39) KESSEL: THE GENUS CALOTARSA 15

(3 miles N. of Boulder Creek): XI-24-62 (Peter Keyes), 1 female. Shasta Coun-
ty: Casile Creek: X-18-59 (E.L.K.), 2 males, 7 females. Pit River, below
Burney Falls: X-17-59 (E.L.K.), 1 female. Sierra County: ? miles N. of Down-
ieville: X-25-62 (E.L.K.), 2 females. Rams horn Forest Campground, 6 miles
V/.of Downieville: X-21-62 (E.L.K.), 1 female. Wild Plum Forest Campground,
5 miles N. of Sierra City: X-26-62 (E.L.K.), 1 female. Siskiyou County: Foiv-
ler Forest Campground: X-17-59 (E.L.K.), 4 females. Hamburg: X-23-59 (E.L.
K.), 10 females. Happy Camp: X-24-59 (E.L.K.), 39 females. Sonoma County:
2 miles S. of Glen Ellen: XI-8-62 (E.L.K.), 6 females. fAonte Rio: XII-6-59 (E.
L.K.), 1 female. Stanislaus County: Turlock Lake State Park: XI-11-60 (E.L.
K.), 2 males, 10 females. Tehama County: Potato Patch Forest Campground:
XI-16-59 (E.L.K.), 1 female. Trinity County: Rush Creek Forest Campground:
X-30-59 (E.L.K.), 5 females; XI-6-69 (E.L.K.), 5 females. Tulare County:
Sequoia National Park, Generals' Highway, elevation 5400 feet: X-29-60 (E.L.
K.), 8 females. 5 miles SE. of Three Rivers, elevation 1000 feet: X-30-60 (E.
L.K.), 2 males, 6 females; XI-25-60 (E.L.K.), 5 males, 26 females; XII-17-60
(E.L.K.), 6females. Tuolumne County: Crane Creek, Yosemite National Park:
X-23-60 (E.L.K.), 5 females. Ventura County: Camp Comfort: XI-30-61 (E.L.
K.), 2 females. Matilija Springs: X-30-49 (M.R.Wheeler), 1 male. SteckelPark:
XI-28-52 (E.L.K.), 1 female, XIM9-61 (E.L.K.)j 1 female. Wheeler Gorge For-
est Campground: XII-1-61 (E.L.K.), 2 females; XII-19-61 (E.L.K.), 1 female.

MONTANA: Sanders County: 9 miles E. of Paradise: W\\\-?>\-62{E.h.K.),
1 male.

OREGON: Benton County: Corvallis: 1-5-15 (L.Childs), 2 females; I-
15-15 (L. Childs), 1 female; XII-25-14 (L.Childs), 1 female. Curry County:
Azalea State Park: X-30-61 (E.L.K.), 2 females. Humbug Mountain State Park:
X-31-61 (E.L.K.), 11 females. McGribble Forest Campground: X-31-61 (E.L.K.),
10 females. Hood River County: Hood River: X-ll-17 (.A.L.Melander), 1 female.
Jackson County: Goldhill: XI-10-61 (E.L.K.), 6 females. Lane County: Hen-
dricks Bridge State Park: XI-9-61 (E.L.K.), 1 female. LiNN County: Cascadia
State Park: XI-7-61 (E.L.K.), 1 female. Marion County: Champoeg State Park:
XI-24-61 (E.L.K.), 1 male, 2 females; XI-5-61 (E.L.K.), 10 females. Yamhill
County: Peavine Ridge, McMinnville: X-22-46 (K.M. Fender), 1 male.

Seasonal distribution. The male from Sanders County, Montana, mention-
ed immediately above, represents not only the most eastern record for the spe-
cies, but the earliest seasonal one as well. This is some three weeks earli-
er than the next earliest record which is from Mill Valley, Marin County, Cali-
fornia. This difference may be accounted for by the more northern latitude of
Montana, and perhaps its higher elevation as well. Early emergence seems to
be associated with both higher latitude and higher elevation, which, in turn,

16 CALIFORNIA ACADEMY OF SCIENCES (Occ. Papers

are associated with more severe climate. In general, the more severe and
longer the winter, the earlier the platypezid season begins. This early begin-
ning of the season makes up for its earlier termination in such climates.

^

Figure 9- Posterior tarsus of the male of C insignis.

As discussed under C pallipes, the males of platypezids, like those of
many other insects, begin to emerge early in the season. It is not surprising,
therefore, that these first two records are for males. The earliest record for
females of C. insignis is for September 24, at Champoeg State Park, Oregon.
For this species the season for adults lasts past the middle of January in its
southern ranges, the latest specimen taken being a female captured at Mill
Valley, Marin County, California, January 19. The latest record for the cap-
ture of a male is for December 8, at San Francisco, Califoinia. The adult sea-
son for C. insignis, therefore, is from the last of August past the middle of
January, the males disappearing by the middle of December.

Host fungus. Although I know of no published records which give the
host fungus of C. insignis, or of either of the other species of Calotarsa, it
is now abundantly clear that the larvae of C insignis commonly feed on Ar-
miliaria mellea, known popularly as the oak-root fungus or honey mushroom.
My own discovery of this fact dates back to 1959 when I reared adults of C
insignis from honey mushrooms which I had collected near the Navarro River
in Mendocino County, California. Since that time I have repeatedly obtained
these flies from larvae infesting Armillariamellea collected from several other
localities in California, including Pfeiffer-BigSur State Park, Monterey County;
Big Basin Redwoods State Park, Santa Cruz County; San Luis Rey Forest
Campground, Riverside County; McConnell State Park, Merced County; Rough
and Ready, Nevada County, and Golden Gate Park, San Francisco County.

No. 39) KESSFX: THE GENUS CALOTARSA 17

Later, while studying material collected by others in the preparation of this
paper, it was found that this species had been reared from Armillaria at Berk-
eley, Alameda County, as long ago as 1936. A specimen from the E. I. Schlinger
collection, dates November 9 of that year, bears this information, as do flies
reared by R. C. Dickson (XII-4-36 and XII-9-36), T.G.H. Aitken(XI-no day-36),
and G.E. and R. M. Bohart (Xl-no day-36). Presumably Aitken and the Boharts
collected their larvae together. Very recently Ireceived five females from E.
I. Schlinger which he had reared from Armillaria taken at Glendale, Los An-
geles County, November 24, 1962.

Emergence times. Much of interest, in addition to the fact that C insig-
w/'s utilizes Armillaris mellea as its host fungus, was revealed by the rearing
experiments. Table I tabulates the data of these rearing records.

These cultures gave surprising results on two counts. In the first place,
the adults did not wait until the following fall to emerge, yet none of the ex-
tensive field-collected material that I have examined consists of anything
but flies which have been taken during the autumn and early winter. In the
closely related genus Clythia we have species (e.g. C. agarici and C poly-
pori) which may develop without a long diapause and may therefore have sev-
eral broods a year, but although the flies of C insignis are large and conspic-
uous enough to attract attention at any season, no one seems to have captured
any of them during the spring and summer. It seems necessary, therefore, to
conclude that the emergence dates given in the table are abnormal ones, re-
sulting from an abnormal environment during pupation. Under ordinary field
conditions, the adults of C insignis do not emerge until after a diapause of
many months, but it is evident that in the artificial environment of uncontrolled
laboratory conditions this diapause may be omitted. It is as though the entire
culture had been physiologically alerted by the adverse conditions of the ab-
normal environment not to wait until the usual emergence time in the autumn,
but rather to start sampling the environment at once on a trial-and-error basis.
In this way some of the individuals of the species may be able to survive and
reproduce. The culture from Pfeiffer-BigSur is particularly interesting in this
respect. It straggled its emergences over a period of almost six months and to
the normal season.

It might be argued that because the larvae of the Pfeiffer-BigSur culture
were collected on December 19, and the first adults did not emerge until Fe-
bruary 9, that the diapause had not been dispensed with, but only shortened.
An attempt had been made to determine the time of pupation for this and the
Big Basin Redwoods cultures. In both cases, the full-grown larvae were slow
in pupating and for several weeks attempted to disperse. It would seem that
this interval between the attainment of full growth for the larvae and the time
of their pupation may be an important period of dispersal in nature as well.

18

CALIFORNIA ACADEMY OF SCIENCES

(Occ. Papers

Table 1. Rearing records for C. insignis, all from California localities and from
Armillaria mellea. The identifications of the fungus specimens
were made by Robert T. Orr and Berta B. Kessel.

County

Locality

Larvae
Collected

Adults
Emerged

Numbersc Sex

Collector

Mendocino

2 miles up
Navarro R.

XII-5-59

1-27-60
n-8-60
n- 18-60
III-1-60
IH-3-60

1 male

3 females

1 female
1 female
1 female

E.L. Kessel

III-20-60

1 male

1 female

Santa Cruz

Big Basin

XI-12-59

IV-5-60

4 males

3 females

E.L.Kessel

Redwoods

IV-6-60

7 males

5 females

State Park

IV-21-60

4 males

3 females

Monterey

Pfeiffer-

XII-19-59

11-9-60

2 females

E.L. Kessel

Big Sur

11-10-60

1 male

3 females

State Park

11-11-60

n-16-60

n-18-60

11-23-60

11-25-60

11-26-60

111-1-60

1II-3-60

ni-8-60

in-lO-60

III-15-60

in-11-60

III-17-60

III- 19- 60

ni-23-60

m-26-60

ni-30-60

IV-6-60

IV- 7-60

IV-11-60

IV- 15-60

IV- 20-60

IV- 24- 60

IV-29-60

lV-2-60

V-4-60

V-6-60

V-10-60

V-13-60

V-19-60

V-21-60

4 males
1 male

4 males
15 males

9 males

15 males

16 males
16 males

22 males

19 males

11 males
7 males

12 males
26 males
43 males
34 males

23 males
21 males

24 males
10 males
28 males
18 males
10 males

5 males
5 males
1 male

30 males

26 males

3 males

20 males

6 females

25 females

2 females
33 females

28 females

12 females
30 females

19 females

29 females

26 females

17 females
6 females
6 females

13 females
25 females

23 females
13 females

18 females
29 females
18 females

5 females

24 females

20 females

3 females
3 females

2 females

3 females
18 females
38 females
13 females
24 females

V-28-60

5 males

29 females

No. 39)

KESSEL: THE GENUS CALOTARSA

19

Table 1.

(Continued)

County

Locality

Larvae
Collected

Adults
Emerged

Number

a SEX

Collector

V-31-60

5 males

26 females

VI- 2- 60

1 male

11 females

■

VI- 7-60

1 male

8 females

VI-9-60

2 females

VI-13-60

3 males

13 females

VI-20-60

14 females

Vl-24-60

1 female

Vl-28-60

1 male

4 females

VII-5-60

1 male

5 females

VII-8-60

'

2 females

'

VlI-11-60

3 females

VII-14-60

1 male

4 females

Vll-15-60

2 females

VII-21-60

1 female

VII-22-60

2 females

VII-26-60

1 female

Nevada

Rough and
Ready

XlI-28-60

1-17-61

1 female

I.Branson

Riverside

Upper San
Juan Forest
C.G.

XII-6-61

VI-31-62

2 males

E.L.Kessel

San Benito

San Juan
Canyon

X- 10-60

IV-20-61

V-18-61

V-24-61

V-26-6.1

V-27-61

1 male
3 males
1 male

1 female

2 females

E.L.Kessel

San

V-28-61

1 male

Francisco

Golden Gate

X- 17-62

XI-20-62

1 female

R.T.Orr

Merced

McConnell
State Park

XI-16-60

III-29-61

2 males

E.L.Kessel

At any rate, pupation of the two cultures in question did not take place until
approximately January 20 which, for the Pfeiffer-BigSur brood, left only about
nineteen days before the first flies emerged. The Golden Gate Park culture
should also be noted in this connection. It produced its lone fly barely a month
after the larvae were collected, certainly leaving no time for a diapause.
The second way in which the cultures produced surprising results was
that the sequence of emergence did not bear out our impression, gained from
field work, that the first flies to emerge are males. In all of the cultures con-
sidered in table I, and from which both males and females emerged, females

20 CALIFORNIA ACADEMY OF SCIENCES (Occ. Papers

appeared on the first day of emergence, and in the Navarro River, Pfeiffer-Big
Sur, and San Juan Canyon cultures, only females emerged the first day. Pos-
sibly this discrepancy from the expected, like the abnormal times of emergence,
maybe attributed to the artificial laboratory environment in which the cultures
were kept. Nevertheless, a second impression gained from field work, viz.,
that the females predominate or occur alone duringthe last part of the season,
is definitely supported by the rearing evidence. The Pfeiffer-Big Sur culture,
with its large numbers and its emergences over a six-month period, indicates
clearly that mostly females are produced toward the end of the season and
that the last flies to emerge are exclusively females. During the last two
months of the six months emergence period, the sex ratio of the emerging flies
consisted of 73 females to 8 males, and the last two weeks yielded 6 females
to no males. In view of these data, it seems proper to amend our field impres-
sions as follows: the first flies to emerge are likely to represent both sexes,
but the males complete their emergences earlier, so that the last individuals
to appear are females. Some of the males live long enough to fertilize these
late-emerging females, whose youth at the time permits them to live on for
several weeks and therefore to oviposit on those host fungi which appear very
late in the season.

OviPOSiTiON. Egg laying by females of C. insignis has been observed by
Peter Keyes, one of my students at the University of San Francisco. While
collecting at Wildwood, 3 miles north of Boulder Creek, Santa Cruz County,
California, on November 24, 1962, he came upon a rotten oak stump on which
many honey mushrooms were growing. Removing some of these fungi and turn-
ing them upside-down, Keyes found the flies engaged in laying eggs. They
were not easily disturbed, and some of them continued to oviposit with the
mushrooms in the reversed position.

In all respects these flies behaved in the manner I have described for
Clythia agarici (Kessel, 1960). The females wandered about over the gill sur-
face, stopping frequently to oviposit. Each fly backed into the egg-laying po-
sition, moving backward into the slit between two gills and sinking so deeply
that her abdomen was hidden and her wing bases were pressed against the gill
surface. In this position her wings were flattened out over the surface of the
pileus, and her hind legs projected more or less beneath them. Each fly re-
mained in this ovipositing position for a few moments, long enough to lay an
egg, and then neatly eased herself out of the slot. The mushrooms were ma-
ture, but not in a state of decomposition.

In the case of C. agarici, oviposition on a particular fungus occurs only
for a period of one day, but Keyes had no opportunity to verify this observa-
tion for C. itisigtiis because he could not return to visit the site the next day.

No. 39) KFvSSHL: THE GENUS CALOTARSA 21

Mating activities. Actual mating pairs of C. insignis have not yet been
observed to my knowledge, but the swarming activities of the males have been
noted repeatedly. I first came across these swarms on October 22, 1945, at
Mill Valley, Marin County, California. They appeared in the late morning and
lasted until late afternoon, and were invariably found in "chimneys" open to
the sky above and formed by irregular rings of trees, usually redwoods.

The swarms often consisted of several hundred flies, all males as evi-
denced by repeated sampling with a long-handled net. The insects flew slowly,,
moving to and fro in rather parallel formation, although rising and falling in
altitude all the while. Such swarms were in evidence every day that I visited
the area for a period of two weeks. Then came a series of heavy rains which
continued for about three weeks. While individual males were still to be found
on the bushes with the females after the rains, no more swarms of them were
seen for the duration of the season, and some of the "chimney" sites which
they had previously occupied had now been taken over for swarming purposes
by Platypezina pacified. It seemed that the storm had greatly reduced the
population of males, but the females were as plentiful as ever. This result is
not unexpected when one considered the amount of energy which the males
must expend as they continue in flight many hours each day within the swarm.
It is probable that the males formed smaller swarms after the storm, but if this
was the case they went unobserved.

I encountered similar swarms at Mill Valley during succeeding years,
and again at Novate, also in Marin County, when I moved to that location. Ac-
cording to his collection labels, W. W. Wirth observed the male swarms of this
species at Berkeley, Alameda County, California, October 31, 1947. Such
swarming of the males is preliminary to mating in all the species of platype-
zids that have been studies adequately (Kessel and Kessel, 1961; 1962a;
1962b).

As noted under the discussion of C. calceata, Snow (1894a) was probab-
ly the first to observe this swarming of the males in platypezids. In fact, he
obtained all but two of his specimens from such an aggregation, the excep-
tions constituting a mating pair which he captured in the air below the swarm.
Snow was not aware of it, but it is now evident from observations on the mat-
ing habits of flat-footed flies which my wife and I have made during the past
few years, that the pair which he caught in his net were descending from the
swarm where they had first embraced.

Our observations on P. pacifica and Protoclythia californicct indicate
that the events leading up to mating are basically the same for platypezids in
general, the swarming of the males differing only in regard to such matters as
the height off the ground and the nature of the "chimney." In the two species
here mentioned, the males wait in the swarm for the approach of individual fe-

22 CALIFORNIA ACADEMY OF SCIENCES (Occ. Papers

males and, as each receptive female comes close enough, she is grabbed by
the nearest male. Copulation is initiated at once, and then the female takes
the initiative to tow the male backwards as they descend to the lower-story
vegetation to complete their nuptial activities. Undoubtedly it was such a de-
scending pair that Snow captured, for we must presume that the mating habits
of platypezids as a family correspond as well as does their preliminary epi-
gamic behavior.

In platypezids, the mating swarm is to be regarded as a device which
serves as a recognition symbol and erotropic stimulus for the species. In all
of the cases which I have observed, the legs of the "dancing" males are
pendant, and in the species of Calotarsa the striking ornamentation of the
posterior tarsi would appear to provide additional signals of this type. The
ultimate in this ornamentation is achieved in the flat-footed flies, C. pallipes
and C insignis, and in the latter particularly, with its great hoof-like appen-
dages attached to the fourth segments and the more spectacular banners fly-
ing from the third segments.

A female of C. i?istgnis, passing a swarm of her males "dancing" in the
darkened woods, could hardly fail to see the display of scintillating flashes
which are emitted as the silvered surfaces of the flags reflect what light is
present to broadcast the species' message of invitation. Plate 1, figure 2 il-
lustrates how these flags, even those of a resting fly, reflect light in dark
surroundings. On a leaf, a female will sit in close proximity to her males and
ignore them completely. Only in the air, activated by the recognition of her
own species' pattern of sexual stimulation, will she respond.

Summary

The genus Calotarsa is known from three species, all recorded only
from North America. Calotarsa pallipes (Loew) is an eastern species, found
thus far from Quebec to North Carolina and westward as far as South Dakota.
The season for this species is from early August to middle November. Calo-
tarsa calceata (Snow) is known only from one locality in New Mexico and has
been collected only in August. Calotarsa insignis Aldrich has a known dis-
tribution from southern British Columbia to southern California and, although
it has not been collected in Washington and Idaho, a specimen was captured
in Montana. The observed season for this species is from late August to mid-
dle January.

Calotarsa insignis is the only species of the genus for which the host
fungus is known, having been reared repeatedly from Armillaria nwllca. Under
field conditions the adults do not emerge until after a diapause of many months,
but under uncontrolled laboratory conditions this diapause maybe abbreviated
or omitted. In one culture, emergences straggled over a period of almost six

No. 39) KESSEL: THE GENUS CALOTARSA 23

months, virtually to the beginning of the normal season. In this way, and in
such abnormal surroundings, the species samples the environment at unusual
times, with the result that some individuals may find a suitable host and be
able to reproduce.

Rearing experiments have demonstrated that full-grown larvae of C. in-
sigtiis have a tendency to disperse before they pupate. These experiments al-
so demonstrated that the first flies to emerge may be either males or females,
although the males complete their emergences earlier. Some of the males live
long enough to fertilize the later-emerging females which survive to oviposit
on the host fungi which appear late in the season. There is normally only one
generation a year. Oviposition has been observed for C. insignis, and it is es-
sentially like that known for Clythia agarici (Willard).

Actual mating pairs of C insignis have not been observed, although the
swarming activities of the males in their "chimneys" have been noted re-
peatedly. Comparison of these swarms with those of other genera indicates
that the epigamic behavior of platypezids in general is similar. The swarm of
"dancing" males is to be considered as both a species-recognition symbol
and an erotropic stimulus for the female. The males always "dance with their
legs pendant, and in the species of Calotarsa the striking ornamentation of
the posterior tarsi should make recognition easier. The ultimate in this orna-
mentation is achieved in C. insignis, with tassels attached to the first two
tarsal segments, a spectacular silvered banner flying from the third segment,
and a great hoof-like appendage projecting from the fourth. A female, passing
a swarm of her males, could hardly fail to see the display of scintillating,
flag-reflected flashes which constitute her species' own message of invitation.

LITERATURE CITED

Aldrich, J. M.

1905. A catalogue of North American Diptera. Smithsonian Miscellaneous Col-

lections, vol. 46, pp. 1-680.

1906. The dipterous genus Calotarsa, with one new species. Entomological

News, vol. 17, pp. 123-127.
Banks, Nathan

1894. Concerning Calotarsa omatipes Townsend. Canadian Entomologist,
vol. 26, p. 88.

Greene, C. T.

I9O8. Note on Platypeza omatipes Townsend. Canadian Entomologist, vol.
19, p. 241.
Johnson, C.W.

I9O8. A note on Calotarsa, and descriptions of two new species oi Callimyia,
Psyche, vol. 15, pp. 58-60.

24

CALIFORNIA ACADEMY OF SCIENCES

(Occ. Papers

Kessel, E. L.

1952.

1960.
1961.

Kessel, E. L
1961.

1962a.

1962b.

LOEW, H.

1865.

Snow, W.A.
1894.

1895.

TOWNSEND, C.

1894a.

1894b.

WiLLISTON, S.

1894.

Rediscovery of Snow's two species of Protoclythia (Dipt era: Clythiidae).
Wasmann Journal of Biology, vol. 10, pp. 359-361.

The life cycle of Clythia agarici (Willard) (Diptera: Platypezidae). Was-
mann Journal of Biology, vol. 13, pp. 263-270.

The Immature stages of Callomyia, with the description of a new spe-
cies of this genus (Diptera: Platypezidae). Occasional Papers of
the California Academy of Sciences, no. 30, pp. 1-10.
., AND BERTA B. KESSEL

Observations on the mating behavior of Platypezina pacifica Kessel
(Diptera: Platypezidae). Wasmann Journal of Biology, vol. 19, pp.
295-299.

Mating behavior and activity-rest periodicity in Protoclythia califomica
(Diptera: Platypezidae). Proceedings of the California Academy of
Sciences, 4th ser., vol. 32, pp. 57-78.

Mating swarms of Platypezidae, with special reference to Agathomyia
cushmani (Diptera), Wasmann Journal of Biology, vol. 20, pp. 289-
292.

Diptera americae septentrionalis indigenea. Berliner Entomologische
Zeitschrift, vol. 9, PP. 127-186.

American Platypezidae. Kansas University Quarterly, vol. 3, pp. 143"

152.
American Platypezidae. II. Kansas University Quarterly, vol. 3, pp.

205-207.

H.T.

A very remarkable and anomalous syrphid, with peculiarly developed
hind tarsi. Canadian Entomologist, vol. 26, pp. 50-52.

Note on the proposed new genus Calotarsa. Canadian Entomologist, vol.
26, pp. 102-103.

W.
Calotarsa omatipes. Canadian Entomologist, vol. 26, p. 116.