THE LARVA OF PELECINUS POLYTURATOR (DRURY) (HYMENOPTERA : PELECINIDAE)

5 Pages·1999·2.4 MB·

PROC. ENTOMOL. SOC. WASH.
101(1). 1999, pp. 64-68
THE LARVA OF PELECINUS POLYTURATOR (DRURY)
(HYMENOPTERA: PELECINIDAE)
Norman F. Johnson, Luciana Musetti, James B. Johnson, and Kerry Katovich
(NFJ, LM) Department ofEntomology, The Ohio State University, 1315 Kinnear Road,
Columbus, OH 43212-1192, U.S.A. (e-mail: [email protected];[email protected].
ohio-state.edu); (JBJ) Division of Entomology, Department of Plant, Soil, and Entomo-
logical Sciences, University of Idaho, Moscow, ID 83844-2339, U.S.A. (e-mail:
[email protected]); (KK) Department of Entomology, 237 Russell Laborato-
ries, University of Wisconsin, Madison, WI 53706, U.S.A.
—
Abstract. The first instar larva and exuviae of the last instar larva of Pelecinus po-
lyturator (Drury) are described, illustrated, and compared with published descriptions of
other larvae of Proctotrupoidea.
Key Words: larval morphology, Pelecinidae, Proctotrupoidea
The application ofcharacters from larval with a diversity of forms without any un-
morphology to the study of relationships derlying organizing principle.
within the Hymenoptera is very uneven. The superfamily Proctotrupoidea s. str. is
There are some good examples of the use- comprised of ten extant families of internal
fulness of immatures as an additional parasitoids. The hosts for three of these
source of data (e.g., Evans 1987), but for (Renyxidae, Austroniidae, and Peradeni-
many superfamilies little or nothing is idae) are unknown, and only a bare mini-
mum
known. Progress in this area is hindered for of information is available for the
several reasons. Most Apocrita are parasit- Monomachidae and Roproniidae. The only
oids of other insects, and the hosts for a families for which immature stages have
number of groups are very poorly known. been described are the Diapriidae (a large
Many species are internal parasitoids; thus group of nearly 2,000 recognized species),
it is difficult to obtain early instars and of- Proctotrupidae (331 described species), and
ten the larvae are highly simplified in struc- Heloridae (a relict group of 10 extant spe-
cies). In total, the larvae ofonly six species
ture.
Within the Hymenoptera a remarkable ar- from this complex have been described. We
ray of larval body plans is found. Clausen report here on the larvae of another family,
(1940) outlined fourteen types among the the Pelecinidae, a small group (only one
parasitic Hymenoptera alone. Some ofthese species currently recognized) of uncertain
are highly simplified, "embryonic," forms, affinities (Rasnitsyn 1980, Dowton et al.
1997).
while others possess well-developed, ex-
aggerated mandibles and caudal appendag-
Materials and Methods
es. Later instars usually converge upon a
generalized, hymenopteriform type. Little Five parasitoid larvae were dissected
phylogenetic pattern has been found amidst from larvae of Scarabaeidae (Coleoptera),
this variety; at present we are confronted and preserved in ethanol. The specimens
VOLUME 101, NUMBER 1 65
were found in the posterior two-thirds of mx) supported anteriorly by narrow stipital
the abdomen of the host. Three final instar sclerite, otherwise lobelike, membranous;
exuviae were found attached to scarab re- maxillary palp, labium, and labial palp un-
mains from which Pelecinus had pupated. differentiated; head supported internally by
Specimens are stored in the collections of extensive, strongly pigmented tentorium
JBJ; the Ohio State University; the Insect (Fig. 4, tn) in shape of central plate with
Research Collection, University ofWiscon- anterior extensions continuous with labral
sin; and El Colegio de la Frontera Sur, San sclerite, lateral arms surrounding base of
Cristobal de las Casas, Chiapas. Illustra- mandibles, and broad posterior bilobed
tions were made using a camera lucida of plate in labial region, a central ovoid fora-
whole specimens under alcohol and exuviae men visible, anterior to this with more
in temporary slide mounts in glycerine jel- strongly pigmented triangular prominence,
ly- anterior apex of triangle produced into
small costa extending into labrum; no pro-
Pelecinus polytur—ator (Drury) legs visible; body with indeterminate num-
Material examined. USA. Michigan, ber of segments, without setae, apex of ab-
Newaygo Co., 18 April 1974, host in soil domen acute; no spirac—les visible.
of oak forest, ex Phyllophaga, one first in- Final instar (Fig. 5). Head capsule with
star; Branch Co., 23 May 1974, hosts in soil posterior sclerotized, pigmented band, oth-
of oak-hickory forest, four first instars, erwise largely membranous; mandible (md)
three from large 5 cm long larvae, probably very small, weakly articulated with head;
Phyllophaga, one from small 2.5 cm larva, antenna, labrum, maxilla, maxillary palp in-
possibly Serica sp. Wisconsin, Marquette distinguishable; labium (lb) visible as me-
Co., 11 August 1992, in sandy soil offorest dial triangular raised surface behind man-
meadow, ex larva of Phyllophaga drakei dibles, with large circular field correspond-
(Kirby) one final instar exuviae; Jackson ing to each labial palp (//?), a small central
Co., 4 June 1992, ex P. drakei, one final area presumably representing opening ofla-
instar exuviae; Oconto Co., 28 May 1996, bial gland (Ig) between palpi; mouthparts
ex Phyllophaga rugosa (Melsheimer), one unsupported by sclerotized pleurostoma or
final instar exuviae. MEXICO. Chiapas, Te- hypostoma; body with 7 pairs of spiracles
nejapa, Balun Canal, 2,300 m, 14 February visible; tracheae well-developed.
1997, ex Phyllophaga obsoleta (Blanchard)
Discussion
third instar, one final inst—ar exuviae.
First instar (Figs. 1-4). Length 3.3-5.3 The exuviae of the last instar larvae are
mm; mandibulate larva (Clausen 1940); associated with pharate adult Pelecinuspo-
head capsule well-developed, covering dor- lyturator, and their identity is unequivocal.
sal and lateral sides ofhead, margins darkly The early instar larvae, however, are strik-
pigmented, sclerotization extending beyond ingly divergent in structure from the exu-
margins, gradually disappearing posterior- viae. Our determination of them was based
ly; epicranial suture (Fig. 2, es) well-devel- on the fact that they were internal parasit-
oped; no indication of eyes; antenna (Figs. oids dissected from larvae of Phyllophaga
1-3, a) indicated by small paired submedial Harris (Coleoptera: Scarabaeidae), the only
papilla; clypeolabral area (Fig. 3, cl) largely recorded host in the United States and Can-
membranous, supported by ovoid sclero- ada. The specimens also were collected in
tized ring, dorsal portion of this ring some- an area in which Pelecinus was very abun-
times incomplete; labrum with two medial dant. Muesebeck (1979) recorded Tiphia
tubercles (Fig. 1, It); mandible (Figs. 1, 3, berbereti Allen, T. tegulina Malloch, T.
md) strongly developed, falcate, bearing a transversa Say, T. vulgaris Robertson, and
small subapical tooth; maxilla (Fig. 1, 3, T. intermedia Malloch (Tiphiidae); Myzin-
PROCEEDINGS OF THE ENTOMOLOGICAL SOCIETY OF WASHINGTON
66
Figs 1-5 Pelecinuspoh'turator, larva. 1-4, Head of first instar 1. Lateral view. 2, Dorsal view. 3. Frontal
view, specimen with mandibles closed. 4, Frontal view, specimen with open mandibles exposmg tentonum. 5
Mouthparts from final instar exuviae, right mandible detached. Abbreviations: a = antenna; cl - clypeolabral
area; es = epicranial suture; lb = labium; Ig = opening of labial gland; Ip = labial palp; It = labral tubercle;
md = mandible; mx = maxilla; tn = tentorium. Scale in mm.
VOLUME 101, NUMBER 1 67
um quinquecinctiim (Fabricius) (Tiphiidae); scribed in H. anomalipes, B. tritoma, and
and Ophion nigrovarius Provancher C silvestril. Phaenoserphus viator lacks a
(Ichneumonidae) as parasitoids of Phyllo- coinplete head capsule, but does have a
phaga. Woodruff and Beck (1989) listed a sclerotized ring surrounding the mouth-
second species of Ophion as well as a num- parts. Distinct antennal lobes are found in
ber ofadditional species oftiphiids and sco- the helorid, Basalys spp. and the proctotru-
liids. We ruled out the aculeates because pids, larger and more prominent than the
they are external parasitoids. Ichneumo- structures found in Pelecinus. We observed
noids usually are characterized by the pos- no prolegs on any of the first instar larvae;
session of a hypostomal spur (Short 1978), these structures have been reported for H.
a structure that was not observed in these anomalipes, P. viator, B. parvulus, and an
specimens. unidentified proctotrupid (Clausen 1940;
Determination ofthe number oflarval in- presumably Nothoserphus scymni Ash-
stars of internal parasitoids requires large mead). Two of our specimens have paired,
numbers of observations of cohorts of nipple-like protuberances beneath the pos-
known age in order to detect structural terior portion of the head capsule (visible
changes associated with molting. This has in Fig. 1). Because of their position, we
not been done yet for any species of proc- hesitate to call these prolegs or to homol-
totrupoid, and no one has yet been able to ogize them with the labial palpi. The num-
rear Pelecinus through its life cycle. We ber of observed spiracles reported varies
could not determine the age ofthe observed from three {B. tritoma, C. silvestrii) to ten
larvae directly or infer their age from pub- pairs {P. viator).
lished observations ofrelated species. Clau- The most striking feature we observed in
sen (1940) stated that the characteristics the first-instar larva was the large tentorial
that set apart mandibulate larvae are lost at endoskeleton. A similar structure was very
the first molt. This was confirmed by Clan- briefly described in P. viator by Eastham
cy (1946) in his studies ofHelorus, another (1929), suggesting that it may not have
proctotrupoid. Therefore, we concluded that been as apparent or strongly pigmented as
the larvae dissected from the hosts must be in Pelecinus. The tentorium is not men-
late first instars. tioned in the other descriptions.
Very little information on the immature The larval specimens were dissected
stages of proctotrupoids exists to form a from hosts in the spring (18 April, 1974; 23
context in which to discuss the structural May, 1974) in Michigan. Therefore, it ap-
features ofPelecinus. Larvae have been de- pears that the species overwinters as late
scribed and illustrated for Helorus anom- first instars within the Phyllophaga larvae.
alipes (Panzer) (Heloridae; Clancy 1946), No more than a single larva was found in
an unidentified species of Basalys West- any one host. Three specimens were recov-
wood (Diapriidae; Simmonds 1952), Basa- ered from large (5 cm) hosts, presumably
lys tritoma Thomson (Diapriidae; Wright et the final instar of the beetle. A fourth was
al. 1946), Coptera silvesthi (Kieffer) (Dia- found in a much smaller larva, either a
priidae; Pemberton and Willard 1918), Par- much younger specimen or a different ge-
acodrus apterogynus (Haliday) (Proctotru- nus, perhaps Serica MacLeay (Coleoptera:
pidae; Zolk 1924), Phaenoserphus viator Scarabaeidae). Host size may contribute to
(Haliday) (Proctotrupidae; Eastham 1929), the large variation in size of adult Peleci-
and Brachyserphus parvulus (Nees ab nus.
Esenbeck) (Proctotrupidae; Osborne 1960).
Acknowledgments
Large, sickle-shaped mandibles have been
reported in the first instar for all these spe- Thanks to Lorena Ruiz-Montoya (San
cies. A sclerotized head capsule was de- Cristobal de las Casas, Mexico) and Daniel
68 PROCEEDINGS OF THE ENTOMOLOGICAL SOCIETY OF WASHINGTON
K. Young (Madison, WI) for the loan of Institution Press, Washington, DC. Vol. 1, 1198
specimens. This material is based in part pp.
upon work supported by the National Sci- Osborne, P. 1960. Observations on the natural enemies
of Meligethes aeneus (F.) and M. viridescens (F.)
ence Foundation under Grant No. DEB- [Coleoptera: Nitidulidae]. Parasitology 50: 91-
9521648. 110.
Pemberton, C. E. and H. F Willard. 1918. A contri-
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