Table Of ContentPROC. ENTOMOL. SOC. WASH.
93(1), 1991, pp. 96-100
LIFE HISTORY STUDIES, HOST RECORDS, AND
MORPHOLOGICAL DESCRIPTION OF GENITALIA OF
EURYTOMA TYLODERMATIS ASUM.
(HYMENOPTERA: EURYTOMIDAE) FROM SOUTH DAKOTA
B. McDaniel and a. Boe
Plant Science Department, South Dakota State University, Brookings, South Dakota
57007.
Abstract. —Eurytoma tylodermatis Ashm. was found to be parasitic on Acanthoscelides
perforatus (Horn) in seed pods ofCanada milk-vetch {Astragalus canadensis L.). Obser-
vations on larval behavior and frequency ofparasitism are discussed. Male and female
genitalia ofE. tylodermatis are illustrated.
Key Words: Acanthoscelidesperforatus, Dinarmus acutus, Astragalus canadensis
EurytomatylodermatisAshm. parasitizes collected from a field nursery at Brookings,
bruchid beetles and numerous other Cole- South Dakota and placed in 0.9-liter glass
optera throughout the eastern and central jars (five to ten racemes perjar in ten jars)
United States (Burks 1979). Bugbee (1967) in 1988 and 1.8-liter paper cartons (ten to
listed 56 host species for E. tylodermatis, twenty racemes per carton in five cartons)
manyofwhichareofeconomicimportance, in 1989. Jars were sealed and maintained
but cautioned that more exact determina- at room temperature. Cartonswere wrapped
tions of host relationships are needed. He with aluminum foil and fitted with a 5-ml
stated that the species can act as either a vial to serve as a trap (Fig. 2). Cartons were
primaryorsecondaryparasiteonbeetlesand placed on a shaded bench in a greenhouse.
moths. Pierce (1908) regarded it as an im- Chalcids that emerged from podsin thejars
portant parasite of the cotton boll weevil during fall of 1988 and bruchids that
{Anthonomus grandis Boheman) in Texas, emerged during spring of 1989 were re-
and Ritcher (1936) recorded its parasitism moved, identified,andcountedinJuly 1989.
ofthe larger apple curculio {Tachypterellus Cartons were checked daily through Octo-
quadrigibbus magnus List) in Wisconsin. ber 1989 and chalcids trapped in the vials
This paper records a new host for E. ty- were identified and counted.
lodermatis, presents descriptions of E. ty- In June 1989, green pods containing de-
lodermatis male and female genitalia, and veloping seeds were dissected in order to
describes observations and data regarding make observations on chalcids parasitizing
larvae and adults of E. tylodermatis asso- A. perforatus larvae. Chalcid larvae found
ciated with Canada milk-vetch in eastern parasitizingbeetlelarvaewereplacedin 5-ml
South Dakota. vials and observed daily until adults
emerged.
Materials and Methods
Genitaliawere removed from ten females
In August 1988 and 1989 mature seed and ten males ofE. tylodermatis. Illustra-
pods (Fig. 1) of Canada milk-vetch were tions were made for both sexes and data
VOLUME 93, NUMBER 1 97
Fig. 2. Papercarton rearingcontainer.
(mean of 30.5 for 10 specimens); spines
widely spaced in laminated bridge region,
close together near fulcral plate region; ful-
cral plate (Ful.Pl.) attachment nearnotched
area (Ful.Pl.Not.) offulcral plate; outerovi-
positorplate(Ops.Ot.Pl.)fusedwith 8thter-
gite (8-Teg.); 8th tergite with row of setae
(8-Teg.Set.) ranging from 41 to 51 (mean
of46.3 for 10specimens),setaecountbegins
with first seta anterior to cercus (Ce.); setae
single adjacent to cercus becoming paired
towardattachmentofouterovipositorplate
and fulcral plate; selal region plated, bor-
Fig. 1. PodsofCanadamilk-vetch{Astragaluscan- dered by dark line that divides fused outer
adensis L.).
ovipositor plate into light and dark pig-
mentedareas; apex of8th tergite with series
of long setae similar in structure to other
were recorded for number of rami spines 8th tergite setae [these setae associated with
andeighth tergite setae ofthe females. Mor- epipygium (Ep.)]; cercus with 5 setae ofdif-
phological terminology is that ofSnodgrass ferent sizes and shapes. Inner ovipositor
(1941). plate (Ops.In.PI.) separated from 2nd val-
vifers (Vf2) by darkened region that con-
Results and Discussion
nectsapodemesofouterandinnerramiand
The following is a description of female the groove in which the fulcral plate fits
and male reproductive structures based on along with monitoring spines (rul.Pl.Sp.);
the20adultsobtainedfromlaboratoryrear- innerovipositorplatewith platedregionex-
ings. tendingtoregionoffusedovipositorsheaths
Fetnale (Fig. 3): 2nd Valvifers (Vf2) (Ops.Sh.); ovipositorsheath notarticulated,
(semicircular sheaths) with two setae near containing the ovipositor sheath ligament
apodemes of laminated bridge (Lam.Br.); (Ops.Sh.Lg.) which connects sheaths in
ramus spines (Ra.Sp.) range from 23 to 35 which the ovipositor is held; ovipositor
on right valvifer (mean of29.6 for 10 spec- sheaths lightly striated with typical series of
imens), and from 25 to 36 on left valvifer eurytomid setae at apex.
98 PROCEEDINGS OFTHE ENTOMOLOGICAL SOCIETY OFWASHINGTON
mereplatesetae(Par.Pl.Set.)locatedonout-
ermarginofcurvedparamereplate(Par.Pl.);
posterior paramere plate setae longer and
larger than anterior paramere plate setae;
anterior paramere plate setae located adja-
cent todigitiapodemes(Dig.Apd.); apex se-
tae similar in size to latter paramere setae;
digitiwithtwofinger-liketeethandaround-
ed projection; each digitus with two pores
on base; digital apodemes short (Fig. 5),
fused to aedeagal apodemes (Aeg.Apd.); ae-
deagalapodemesprotrudefromcaulis(Ca.);
paramereplates(Par.Pl.)andVolsellarplates
(Vos.Pl.) fused to caulis with pigmentation
being darker on the sides of reproductive
apparatus and lighter in the center; caulis
forms opening below digiti in which aedea-
gal apodemes are connected to muscles of
the 8th tergite. There is a narrow nonpig-
mented membraneconnectingtheaedeagus
totheepipygiumand8thtergite. Thismem-
brane is beset with small spine-like setae.
The membranous portion ofthis structure
surrounds the aedeagus and contains two
acorn-like setae. This structure is attached
Fig. 3. OvipositorofEurytomatylodermatisAshm. to the aedeagus and apparently plays a role
Abbreviations:(Lam.Br.)Laminatedbridge;(Ra.)Ra-
mus;(Ra.Sp.)Ramusspines;(Vf2)2ndValvifer(Semi- in exsertion and retrieval ofthe entire male
circular sheet); (FuLPLSp.) Fulcral plate spines; reproductive apparatus as well as the ae-
(Ful.Pl.Not.)Fulcralplatenotch;(Ful.Pl.)Fulcralplate; deagus.
(Ops.In.Pl.) Ovipositor inner plate; (Ops.Ot.Pl.) Ovi-
positorouterplate;(Ops.Sh.Lg.)Ovipositorsheathlig- Parasitic Behavior
ament; (8-Teg.) 8th tergite; (8-Teg.Set.) 8th tergite se-
Information on behavior of E. tyloder-
tae; (Ops.Sh.) Ovipositor sheath; (Ce.) Cercus; (Ep.)
Epipygium. matislarvaewasobtainedbysplittinggreen,
well-developed seed pods along their septa
to expose seeds in the chambers ofeach of
Male(Figs. 4, 5): reproductive apparatus the two locules. On July 18, 1988, we
with 4 dorsal aedeagal sensory pores observed a pinkish-white larva that was
(Aeg.S.Por.); aedeagal striae (Aeg.Str.) ex- feedingon an/I.perforatuslarva. Agrayish-
tend from posterior aedeagal sensory pores black, pubescent hatched egg, which resem-
to beyond anterior aedeagal sensory pores; bledE. tylodermatiseggs (Pierce 1908), was
aedeagal sensory pores may be paired or attached to the bruchid larva. The pod loc-
staggeredondorsal surfaceofaedeagus(Fig. ulecontainingtheparasiticlarvaanditshost
4); ventrally apex ofaedeagus with five sen- was placed in a 5-ml vial and stored at
sory pores on each side; these smaller than room temperature. Dailyobservationswere
dorsal pores; aedeagus (Aed.) elongated ca- made and on July 22 the parasitic larva
pableofextendingbeyond digiti (Dgi.); par- crawled out of the locule, defecated, and
amereswiththreesetae;apexsetaenormally pupated. By July 26 the pupa had become
hidden between digiti and aedeagus; para- solid black except for prominent reddish-
VOLUME 93, NUMBER 1 99
_AegS Por
Aeg
__ParPI Set
Dgi
Par PI Set
Dgi Apd
F Par PI
.Vos PI
Aeg Apd
Figs. 4, 5. Male reproductive apparatus ofEurytoma tylodermatisAshm., dorsal and ventral, respectively.
Abbreviations: (Aeg.) Aedeagus; (Par.Pl.Set.) Paramere plate setae; (Par.Pl.) Paramere plate; (Aeg.S.Por.) Ae-
deagalsensorypores;(Aeg.Str.)Aedeagalstriae;(F.Par.Pl.)Fusedparamereplate;(Ca.)Caulis;(Vos.Pl.)Volsellar
plate; (Aeg.Apd.) Aedeagal apodemes; (Dgi.) Digiti; (Dgi.Apd.) Digiti apodemes.
brown compound eyes. On July 30 an adult outnumberedfemalesby67%whilefemales
female oiE. tylodermatis emerged and was of E. tylodermatis outnumbered males by
one ofthe ten females studied forthe struc- 52%. The number of A. perforatus adults
ture of the genitalia. These observations reared in 1988 was 70, indicating that ap-
made it possible to recognize E. tyloder- proximately 35 and 24% ofthe beetles were
matislarvae in subsequent pod dissections. parasitized by D. acutus and E. tyloder-
NumbersofadultE. tylodermatisandthe matis, respectively. Since D. acutus out-
pteromalid Dinarmus acutus Thomson numbered E. tylodermatis by approximate-
reared from inflorescences ofCanada milk- ly 50%in 1989 rearings, thepteromalidwas
vetch in 1988 and 1989 are presented in the more predominant parasite of A. per-
Table 1. Total numbers recorded of each foratusin thisstudy. Thesedataagreeclose-
specieswere 68 and 1 12 forE. tylodermatis ly with a previous study on the effects of
and D. acutus, respectively. Male D. acutus parasitism by D. acutus on Canada milk-
100 PROCEEDINGS OFTHE ENTOMOLOGICALSOCIETY OF WASHINGTON
Table 1. Numbersofparasiticchalcidsrearedfrom
Canada milk-vetch pods infested with the bruchid
Acanthoscelidesperforatus.
