Last instar larva of Microstigmus nigrophthalmus Melo - SciELO

4 downloads 59 Views 911KB Size Report
ABSTRACT. The last instar larva of MicrostiglllLlS nigroplllllllimus Melo, 1992 is described. It markedly differs from that of M. comes Krombein, 1967 the on ly ...
Last instar larva of Microstigmus nigrophthalmus Melo (Hymenoptera, Crabronidae, Pemphredoninae), with notes on biology Sandor Christiano Buys

1

ABSTRACT. The last instar larva of Mi crostiglllLlS nigroplllllllimus Melo, 1992 is descri bed. It markedly differs from that of M. comes Krombein, 1967 the only other species in the genus whose mature larva have been described, for features as follows: presence of spinnerets: setae on the labrum, maxillae and labium; mandibles with tridentate apex and a bidentate lateral projection; lack of the conical supranal process. Notes on habitat, structure, and content of nests are also presented. KEY WORDS. M icrosriglllus Iligrophrhallllus , sphecoid wasp, morphology, larva. biology, behaviour, Brazil

Microstigmus Ducke, 1907 is a Neotropical genus with 29 described species (MELO & MATTHEWS 1997). This genus seems to be unique among sphecoid wasps in presenting species with eusoc ial behavi our (M ATTHEWS 1968). The mature larva of only one species was described in detail: Microstigmus comes Krombein , 1967 (EVANS & MATTHEWS 1968). Microstigmus nigrophthalmus Mel o, 1992 is a recentl y described species that progressively provision its nests with Cicadellidae nymphs (MELO 1992). Herein the last larval instar of this species is described and biological notes are presented. The description presented below is based on two last instal' larvae collected on the National Park of Floresta da Tijuca, Rio de Janeiro State, Brazil , 3-VI-2000. However, the morphometric features were measured in on ly one specimen. Others nests were found on the National Park of Serra Orgaos, also in Ri o de Jane iro State, January, 2000. The techniques for study ing larvae of Apoidea have been discussed by MICHENER (1953) and EVANS & LI N ( 1956). Voucher specimens have been deposited in the collection of Department of the Zool ogy of the Uni versidade Federal do Ri o de Jane iro. RESULTS

Microstigmus nigrophthalmus Melo, 1992 Last instar larva (Figs 1-5)

Body. Fusiform, white, 7 mm long and about 1.5 mm in maximum width (on the thorax). Pleural lobes undistingu ished on thorax , sma ll and poorly distingui shed on abdomen. Integument smooth , without setae or spi nes. Spiracles unpi gmented , inconspicuous; 20 to 25 ~m in diameter, en larging more or less progress ively toward the anterior portion of the body. 1) Laboratorio de Entomologia, Departamento de Zoologia, Universidade Federal do Rio de Janeiro. Caixa Postal 68044, 21944-970 Rio de Janeiro, Riode Janeiro, Brasil. Revta bras. Zoo!. 19 (3): 677 - 679, 2002

Buys

678

1

':

., ;"

., :: "

• ;;-Y'

3

5

Figs 1-5. Microstigmus nigrophthalmus, last instar larva. (1) Body, lateral view; (2) head , frontal view; (3) labrum and epipharynx, frontal view; (4) mandible as seen in frontal view of the head ; (5) dissected mandible , frontal view.

Head. Unpigmented, except for the mandibul ar teeth , including th ose o n the lateral proj ecti on; 570 iJm wide and 535 iJm lo ng. Antennal orbits c ircul ar, 20 iJm in di amete r; ante nn al pap ill ae conical, about 38 iJ m long. Parieta l bands and coronal suture not visible. Mouthparts . Labrum semicircular; 55 iJm in he ight; w ith a few sensi ll a near the margin and scattered setae. Epipharyn x with minute spines sparsely dis tributed on the marginal portio n. Mandibles 2 10 iJm long and 125 iJm in maximum width; broad basally, abruptl y tapering to a u'identate apex; with a bidentate latera l projecti on. M ax ill ae with two setae, each seta about 12 iJm long; max ill ary palpi conical, about 37 iJ m long. Galeae absent, but a pair of sma ll sens ill a present in the sa me pos iti on. Lac ini al area with small , sparse ly di stributed sp in es. Labial pa lpi conical, abo ut 25 iJm long. Spinnerets truncate apically, abo ut 30 iJm lo ng. Bi o logy. The nests were found suspended under the roof of houses in areas with adjacent Atlantic forest. They consist of a g lobul ar sac made of small frag me nts of wood aggregated with silk. A petiole made of si lk alone, w ith 7-18 mm lo ng (n = 3), attaches the nest to the substrate. More rarel y othe r pl ant deb ri s, as stame ns and leaf fragments , are fo und o n the nest formation. The wasps e nter the nest th ro ugh an oval opening near the base of the peti ole. The internal nest surface is coated w ith Revta bras. Zool. 19 (3): 677 - 679,2002

Last instar larva of Microstigmus nigrophthalm us ...

679

silk. The bottom is divided in up to ten cell s, all of them with about the same size. Prey remains were not fo und in the cell s. The nest found in the National Park o f Floresta da Tijuca had the fo ll owing content: one egg attached to the bottom o f the cell ; two immature larvae ; th ree las t instar larvae; three pupae; and one empty cell.

DISCUSSION The mature larva of M. nigrophthalmus di ffe rs markedl y fro m that of M. comes in several features: presence of spinnerets; setae on max ill ae, labium and more rarely on labrum ; mand ibles with tridentate apex and a bidentate lateral projection; a pair of sensilla in the position usuall y occupied by the galeae in other Hymenoptera; lack of the conical supranal process. The presence of spinnerets in M. nigrophthalmus is surpri sin g, since thi s species does not spin cocoons. MELO & EVANS ( 1993) comment that the larvae of M. xylicola Melo, ) 993 and M. similis Melo, 1993, two closely related species, have spinnerets and spin cocoons. On the other hand, M. comes apparently has no spinnerets and does not spi n cocoons (EVANS & MATTHEWS 1968). Microstigmus nigrophthalmus seems to be in an intermediate evoluti ve stage between the species with fu nctional spinnerets, that spin cocoons, and spec ies without spinnerets. Possibly the spinnerets are not functional in M. nigrophthalmus, but it is necessary a bi ological survey to evaluate the possibility that this species use the spinnerets in ac ti vities other than spi nnin g cocoons. Ev ANS & MATTHEWS ( 1968) suggest that the spin ul ose lobe on the in ner margi n of the mandibles o f M. comes may be an adaptation for feedi ng upon Collembola. In fact, the mandib les of M. nigrophthalmus lack thi s structure. On the other hand , they have a bidentate lateral projection which may be correlated with the habit of this spec ies feed ing upon Cicadellidae. ACKNOWLEDGEMENTS. I thank Cinara Silva and Marcello Giffoni for helping to collect the wasps and their nests and Marcio Felix, Alexandre Rosas, and two anonymous referees fo r comments on the manuscript.

REFERENCES EVANS, H.E. & R.W. MATIHEWS. 1968. The larva of MicrostiglllllS comes, with comments on its relationship to other genera (Hymenoptera, Sphecidae). Psyche 75 (2): 132- 134. EVANS, H.E & C.S. LIN. 1956. Studies on Ihe larvae of digger wasps (Hymenoptera: Sphecidae). Part I. Trans. Amer. En!. Soc. 81: 131-153. MATIHEWS, R.W. 1968. MicrostifilllllS comes: sociality in a sphecid was p. Science 160: 787-788. MELD, G.A.R. 1992. Duas novas especies de MicrosliglllllS Ducke, 1907 (Hymenoptera, Sphecidae). Revta bras. Ent. 36 (3): 663-670. . MELD, G.A.R. & H.E. EVANS. 1993. Two new MicrostifilllllS species (Hymenoptera, Sphecidae), with description of their parasite, GOlliUZllS lIIicrostifi llli sp. n. (Hymenoptera, Bethylidae). Proc. En!omol. Soc. Wash. 92 (2): 258-263. MELO, G.A.R. & R.W. MATIHEWS. 1997. Six new species of Microstigl1llls wasps (Hymenoptera: Sphecidae), with notes on biology. Jour. at. Hist. 31: 42 1-437. MICHE ER, C. D. 1953. Comparative morphological and systematic studies of the bees larvae with a key to the families of hymenopterous larvae. Vniv. Kansas Sci. Bull. 35: 987- 11 02. Rece ived in 03.VII1.2001 ; accepled in 1S.VII .2002.

Revta bras. Zoo I. 19 (3) : 677 - 679, 2002