A new species of Dasineura (Diptera: Cecidomyiidae) infesting pinxterbloom azalea flowers in Maryland and Washington, D.C

5 Pages·1996·3.8 MB·

by  R J Gagn

PROC. ENTOMOL. SOC. WASH.
98(2), 1996, pp. 228-232
A NEW SPECIES OF DASINEURA (DIPTERA: CECIDOMYIIDAE)
INFESTING PINXTERBLOOM AZALEA FLOWERS IN
MARYLAND AND WASHINGTON, D.C.
RAYMOND J. GAGNE
Systematic Entomology Laboratory, PSI, Agricultural Research Service, U.S. Dept. of
Agriculture, % National Museum of Natural History, MRC 168, Washington, DC 20560,
U.S.A.
Abstract.(cid:8212)A gall midge (Diptera: Cecidomyiidae) new to science, described and named
here as Dasineura praecox, destroys the flower buds of pinxterbloom, Rhododendron
periclymenoides (Ericaceae). Its biology is unique for Dasineura because adults emerge
and oviposit in autumn instead of in spring. Larvae pass the winter as pharate larvae and
begin to feed in late winter before the ground is unfrozen.
Key Words: gall midge, Dasineura, pinxterbloom, Rhododendron
Pinxterbloom azalea, Rhododendron per- Larvae quickly hatch and, sometimes fol-
iclymenoides (Michaux) Shinners, blooms lowing a short period of relocation, soon
in late April in the vicinity of Washington, begin feeding. The biology of this new spe-
D.C. Among the showy pink flowers can cies of Dasineura is unique in that adults
also be seen flower buds that have been emerge and lay their eggs in the fall. Eggs
aborted. Lying among the scales and flower develop rapidly as in other species, but the
parts of the aborted buds are yellow gall fully developed larvae inside do not hatch
midge larvae less than 3 mm long. By the until late winter.
end of April, these larvae have dropped to Two other gall midges are known to at-
the ground and burrowed into the soil. Af- tack the genus Rhododendron in eastern US
fected buds then succumb to rot and die. and should not be confused with the new
Earlier notice of this damage to pinxter- species. These are Clinodiplosis rhododen-
bloom was given in Gagné (1993, 1994b). dri Felt, which rolls and distorts young
A notice on the biology of this new species leaves of Rhododendron catawbiense Mi-
with color photographs of its damage and chaux and R. maximum L. (Specker and
life stages is given elsewhere (Gagné 1995). Johnson 1988), and the less well known As-
The gall midge responsible is described phondylia azaleae Felt which infests leaf
here for the first time and named Dasineura buds of R. periclymenoides and R. prino-
praecox. phyllum (Small) Millais (Gagné 1989).
Most gall midges and all other Dasineura Methods.(cid:8212)I observed the progress of the
Species in northeastern North America new species found in woods on the South
whose biologies are known overwinter as Farm of the Beltsville Agricultural Re-
full-grown larvae, either in the ground or in search Center, Beltsville, MD, from spring
plant tissue. They pupate in spring and 1993 to autumn 1994. Full-grown larvae in-
adults emerge a short time later to lay eggs tended for rearing were placed in a pot
on or near the newly developed plant tissue. filled with damp peat moss. The pot was
VOLUME 98, NUMBER 2 229
ADULT
V first instar fully developed
EGG
ist
INSTAR
2nd
INSTAR
3rd
INSTAR
PUPA
TTaLz
Fig. 1. Development of Dasineura praecox over period of one year. End points of bars are approximate, but
for the pupa they are estimated only.
kept inside a covered cardboard shoebox immediately burrowed beneath the surface.
with a clear glass vial affixed to one end to There the larvae spun ovoid, white cocoons
attract emerging adults to the light. The vial in which they curled in a (cid:8220)u(cid:8221) shape and
was checked periodically, and the peat moss became still. I did not eee when the
kept damp. Some larvae and adults were larvae entered the pupal stage, but larvae
killed and stored in 70% ethyl] alcohol. Spec- had not yet pupated by July 30, 1994. Adults
imens for microscopic study were mounted emerged between October 1 and October 22.
on glass slides in Canada balsam, using the The surface of the peat moss from which
method outlined in Gagné (1989, 1994a). they emerged was covered with white pupal
All the study specimens are deposited in the exuviae, so the fully developed pupae had
U.S. National Museum of Natural History crawled from the cocoons to the surface of
(USNM). In the description that follows, an- the peat before adults emerged.
atomical terminology of the adult stage fol- Eggs were found between outer bud
lows McAlpine et al. (1981) and that of the scales of flower buds collected in the field
larval stage follows Gagné (1989). on November 8, 1993. Eggs were elongate-
Biology.(cid:8212)Fig. 1 summarizes the life cy- ovoid, set side by side in groups of 10 or
cle of D. praecox. In mid-April, 1993, up to more. No eggs were found among the pri-
75 mature, yellow, third instar larvae were mordial flowers, possibly because the tightly
found among the flower parts and bud scales overlapping inner bud scales prevented entry
of unopened flower clusters. Larvae were of the ovipositor. Eggs collected November
quiescent and apparently no longer feeding, 8 contained quiescent, fully developed first
their heads directed towards the bud apex instar larvae. All heads were pointed toward
and not engaged with the plant. For two the bud apex. Upon hatching in spring the
weeks in April, 1994, larvae lay in the flow- larvae were in position to crawl directly up-
er buds, although when disturbed they be- ward, around the top of the outer bud scales,
came active and quickly wriggled out of the and then downward into the flowers.
buds. On the day following a heavy rain on Stationary, whitish first instars about 0.4
April 28, 1994, no larvae remained in the mm long, were first noticed on February 23,
buds. Upon dropping to the ground, larvae 1994, lying on the surface of stamens and
230 PROCEEDINGS OF THE ENTOMOLOGICAL SOCIETY OF WASHINGTON
pistils. Until March 15 when the flower parts put broadly rounded. Frons with setae and
of normal and infested flowers were only be- scales. Labella hemispherical, each with 8(cid:8212)
ginning to swell, larvae grew only to 0.5 10 setae. Palpus 4 segmented. Male antenna
mm long. By March 17, 1994, the first in- with 15-17 flagellomeres, the third as in
stars were noticeably larger, up to 0.6 mm Fig. 2. Female antenna with 15-16 flagel-
long, and appeared to be more motile. Mi- lomeres, the third as in Fig. 3.
nute brown areas were noticeable on the pis- Thorax: Scutum with 2 lateral and 2 dor-
tils or stamens near apparent feeding points. socentral rows of mixed setae and scales.
By March 25, 1994, larvae still had not Scutellum with a group of setae on each
molted but the brown spots were more pro- side. Mesanepisternum covered with scales
nounced and the flower parts showed some on dorsal third. Mesepimeron with 11(cid:8212)15
distortion. By April 4, all larvae had molted setae. Wing with R,; joining C anterior to
to the second instar. They were greenish wing apex. Claws toothed, empodia as long
white and about 1.6 mm long. Stamens and as claws.
pistils in infested buds showed some defor- Male abdomen: First through fifth ter-
mation and more extensive brown scarring. gites entire, rectangular, with single, unin-
Both infested and uninfested buds were en- terrupted, posterior row of setae and scat-
larging, but none were yet open. tered setae anteriorly; sixth tergite as for
On April 8, second instars were notice- fifth except that anterior setal row inter-
ably larger, about 2.3 mm long. Flowers rupted mesally; seventh tergite unsclero-
parts showed conspicuous distortion and tized caudomesally, with 2(cid:8212)3 setae poster-
scattered brown spots. By Apr. 12 the sec- olaterally, scattered scales laterally; eighth
ond instars were about 2.5 mm long. At this tergite reduced in size, bare except for an-
time stamens and pistils of uninfested buds terior pair of trichoid setae. Genitalia (Figs.
were elongating and the petals becoming 4(cid:8212)6): cerci rounded apically, with several
reddish, and new leaves were emerging in setae along posterior margin; hypoproct
straight, narrow fascicles about % inch long. with two long narrow lobes, each with dis-
By April 14 most larvae had molted to tal seta; claspettes elongate, attenuate, with
the third instar. These were yellow and dorsobasal lobes; gonocoxite cylindrical,
about 2.5 mm long. Third instars apparently unlobed; gonostylus cylindrical, tapered
did not feed, but crawled away from the from base to apex, setulose at base, striate
stamens and pistils, repositioned themselves beyond to short distal tooth.
head outwards among bud scales, and be- Female abdomen (Figs. 7-8): First
came inactive. On April 20, 1994, unin- through sixth tergites rectangular, with sin-
fested flowers lengthened and unfurled gle posterior row of setae, anterior pair of
quickly while infested buds remained trichoid setae, and almost completely cov-
closed. On April 25, 1994, uninfested pinx- ered with scales elsewhere; seventh tergite
terbloom flowers were in full bloom. Lar- much narrower, with double row of poste-
vae still remained in the flowers until three rior setae and scattered scales; eighth tergite
days later when, evidently in response to a much longer and divided into two elongate
heavy rain, the larvae left the buds and sclerites; distal half of ovipositor elongate,
dropped to the ground. about 6 times length of sixth tergite; cerci
fused, cylindrical, slightly bilaterally flat-
Dasineura praecox Gagné, NEW SPECIES
tened, basal two-thirds with widely scat-
(Figs. 1-10)
tered, short setae, distal third with several
Adult.(cid:8212)Wing length: male, 1.8(cid:8212)2.0 mm short, thick setae, the entire surface covered
(n = 8); female 2.0(cid:8212)2.2 mm (n = 8). with patches of short setulae; hypoproct
Head: Eyes 5-6 facets long at vertex; narrow, elongate.
facets circular, contiguous. Vertex of occi- Larva.(cid:8212)First instar: white; length, 0.4(cid:8212)
VOLUME 98, NUMBER 2 231
SN Xx ce
oe\ SorNue cay, a rs
\ EN eC Re Seana
\ipe \ IX LS SI 11 (cid:8220) 0)
NGS Se Li C Se 1) SS
Rouse 4 a
10 Sersse fs
9 BCA ul L
Figs. 2-10. Dasineura praecox. 2, Male third antennal flagellomere. 3, Female third antennal flagellomere.
4-6, Male genitalia: 4, gonopod, cerci, and hypoproct (dorsal); 5, parameres and aedeagus (dorsal); 6, parameres,
aedeagus, and gonopod (ventral). 7, Female abdomen, sixth segment to end (lateral). 8, Female fused cerci with
detail of surface (lateral). 9, Third instar spatula with associated papillae, with detail of one group of lateral
papillae. 10, Third instar eighth and terminal segments (dorsal).
DBD; PROCEEDINGS OF THE ENTOMOLOGICAL SOCIETY OF WASHINGTON
0.6 mm.; integument smooth; spiracles on artificial, catchall category and contains
prothoracic and eighth abdominal segments. species of the tribe Oligotrophini that have
Second instar: greenish-white to white; four palpal segments, toothed tarsal claws,
length, 1.6(cid:8212)2.5 mm.; integument smooth; a shortened R; wing vein that meets the
spiracles on prothoracic and first through costa anterior to the wing apex, and the full
eighth abdominal segments. Third instar: basic complement of larval papillae for the
yellow; length, 2.5(cid:8212)2.6 mm; integument ru- tribe. The new species resembles in some
gose; spiracles on prothoracic and _ first ways Dasineura oxycoccana (Johnson), a
through eighth abdominal segments; spatula species that infests buds of Vaccinium spe-
(Fig. 9) clove shaped; papillae basic for su- cies. The male and female genitalia of both
pertribe present (Gagné 1989); terminal pa- species are superficially similar. The female
pillae (Fig. 10) with 8 setae of equal length cerci of both species bear several thick, sub-
(2 not shown, hidden from view dorsally). apical, sensory setae. Dasineura oxycoc-
Pupal exuviae.(cid:8212)White. Face smooth, cana, however, is a smaller species with a
clypeus with two papillae at each side near wing length of only 1.2(cid:8212)1.4 mm and only
base, one of each pair with short seta. Ce- 13-14 antennal flagellomeres. The two spe-
phalic setae and prothoracic spiracles elon- cies differ greatly in their biology: while D.
gate. Abdomen covered dorsally with spic- praecox has one generation per year and its
ules, those mesoanteriorly on second to adults appear in autumn, D. oxycoccana has
eighth segments enlarged, spinose. two or more generations per year and its
Holotype.(cid:8212)Male, emerged X-1993 from adults appear in spring and summer (Gagné
larva collected IV-23-1993 in flower bud of 1989).
Rhododendron periclymenoides, South
Literature Cited
Farm, Beltsville Agricultural Research Cen-
ter, Beltsville, Maryland, R. J. Gagné, de- Gagné, R. J. 1989. The Plant-Feeding Gall Midges of
posited in the USNM. Other material ex- North America. Cornell University Press, Ithaca,
amined, all from R. periclymenoides, New York. xiii and 355 pp and 4 pls.
. 1993. [Notice of new record of gall midge in
mounted on slides and deposited in the
flower buds of Rhododendron nudiflorum in
USNM: 7 males, 8 females, same data as Maryland] Jn Minutes for Meeting of May 6,
holotype; 5 pupal exuviae, same data as ho- 1993. Proc. Entomol. Soc. Wash. 95: 653. 1993.
lotype; 32 first instars, collected [II-10- . 1994a. The Gall Midges of the Neotropical
1994, same locality as holotype; 13 second Region. Cornell University Press, Ithaca, New
York. xv and 352 pp.
instars, collected I[V-4-1994, same locality
. 1994b. [Note on autumn emergence of a gall
as holotype; 8 third instars, collected 23-IV- midge in flower buds of Rhododendron nudiflo-
1993, and 6 third instars, collected IV-14- rum in Maryland] In Minutes for Meeting of Dec.
1994, all same locality as holotype; 10 third 2, 1993. Proc. Entomol. Soc. Wash. 96: 384.
. 1995. A new gall midge pest infesting pinx-
instars, collected 22-IV-1994, Fern Valley,
terbloom azalea flowers in Maryland and Wash-
US National Arboretum, Washington, D.C.
ington, D.C. The Azalean 17: 37-38.
Additional specimens of all stages in alco-
McAlpine, J. EF, B. V. Peterson, G. E. Shewell, H. J.
hol in USNM. Teskey, J. R. Vockeroth, and D. M. Wood, eds.
Etymology.(cid:8212)The specific name praecox 1981. Manual of Nearctic Diptera, Vol. 1. Res.
is an adjective meaning precocious, with ref- Branch, Agric. Canada, Mon. 27. vi + 674 pp.
Specker, D. R. and W. T. Johnson. 1988. Biology and
erence to the adults(cid:8217) autumn flight period and
immature stages of the rhododendron gall midge,
early eclosion of the larvae in late winter.
Clinodiplosis rhododendri Felt (Diptera: Cecido-
Remarks.(cid:8212)The genus Dasineura is an myiidae). Proc. Entomol. Soc. Wash. 90: 343-355.