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Comprehensive Description

provided by Smithsonian Contributions to Zoology
Hylomesa anomala

This small species shares with H. ugandensis (Turner) the distinction of having the only females of the genus in which both the dorsum of the pronotum and of the first abdominal tergum lack a transverse anterior ridge. It differs from H. ugandensis in having the posterior fourth of the sixth tergum shagreened rather than polished, in having the mesopleural disk strongly produced in middle, and in having the anterior half of dorsal surface of pronotum coarsely and contiguously punctate in longitudinal rows.

The male of H. anomala lacks an anterior ridge on the pronotum but has a well-developed transverse ridge at base of disk of first abdominal tergum. It shares with H. dimidiaticornis (Bingham) the distinction of being the only Hylomesa male with specialized dense vestiture on any of the abdominal sterna. This is present on the fifth and sixth sterna in H. dimidiaticornis but on only the sixth in H. anomala.

The three males were captured while flying around a standing dead trunk in a wooded ravine through which a small stream flowed. The single female was taken while flying around a fallen dead trunk in a similar area about a kilometer away.

HOLOTYPE.—, Sri Lanka, Kandy District, Thawalamtenne, 8 Sep 1980, K.V. Krombein, P.B. Karunaratne, T. Wijesinhe, L. Jayawickrema, V. Gunawardane (USNM Type 100283).

MALE.—Length 9.7 mm, forewing 6.8 mm. Black, head except tip of mandible, ocellar triangle, hypostomal area, and last eight flagellar segments light red, abdomen with faint blue reflections; basal third of forewing clear, apical two-thirds infuscated and with blue reflections.

Clypeal keel strong, present on basal three-fifths, median lobe of clypeus with a narrow shallow emargination separating the 2 weak teeth; distance from apex of frontal platform to occiput 0.93 times the width across eyes; front with mostly contiguous to subcontiguous pits; vertex with quite scattered, smaller punctures; ocellocular distance 1.5 times the postocellar distance and 0.8 times the ocelloccipital distance; occipital carina complete; median flagellar segments 1.3–1.4 times as long as wide.

Pronotal disk not ridged anteriorly, the anterior half with elongate pits arranged more or less in transverse rows, posterior half with scattered small punctures; scutum and scutellum with coarse, shallow contiguous to subcontiguous pits; mesopleuron with coarse to larger subcontiguous pits; metapleuron with coarse, relatively close longitudinal ridges; propodeal dorsum with a narrow depressed median channel laterad of which are irregular pits, apex with strong transverse ridge; lateral surface anteriorly with ridges continuing from metapleuron, posteriorly with subcontiguous pits; posterior propodeal surface with smaller, closer pits.

First tergum with strong transverse ridge anteriorly, behind this the disk with scattered large to small punctures; sterna 3–5 with scattered small punctures which are more concentrated anteriorly and bearing short suberect hair; sternum 6 with a patch of dense longer suberect setae on posterior two-thirds extending almost to sides; genitalia (Figure 40) with gonostyle more slender, most of inner surface bare except for a row of close long setae near dorsal edge, cuspis narrower and densely setose on inner surface, digitus extremely slender and with very few setae on inner surface.

ALLOTYPE.—, same label data as holotype except 740–760 m, 16–18 Sep 1977, K.V. Krombein, P.B. Karunaratne, T. Wijesinhe, M. Jayaweera (USNM).

FEMALE.—Length 13 mm, forewing 9 mm. Black, head except apex of mandible, hypostomal area, and flagellum light red, abdomen with weak, metallic blue reflections; basal third of forewing lightly infumated, apical two-thirds infuscated and with bronze to blue reflections.

Head elongate, width across eyes equal to length from antennal insertions to occiput, sides parallel behind eyes; clypeal keel weak, present only on basal two-thirds; clypeal margin with median teeth weak, slightly separated; median frontal sulcus extending halfway to anterior ocellus; lower half of front with punctures somewhat more separated than in H. longiceps, upper half of front with widely separated punctures; vertex with very few scattered punctures behind ocelli, virtually impunctate elsewhere; ocellocular distance 2.2 times postocellar distance and 0.58 times ocelloccipital distance; anterior ocellus slightly closer to antennal tubercles than to occiput; head beneath with rounded posterolateral angles; distance between occiptal and hypostomal carinae subequal to length of hypostoma.

Anterior margin of pronotal disk not ridged, anterior two-thirds with coarse, confluent punctures arranged in longitudinal rows, the rows becoming more separated at sides, posterior third with scattered small punctures; scutum with coarse punctures, separated anteriorly by about the diameter of a puncture and contiguous posteriorly; scutellum with more separated punctures; mesopleural disk produced anteriorly in middle beyond concave anterior face of sclerite, discal punctures separated by about half the diameter of a puncture but more crowded posteriorly; inferior surface of hind femur sharply right-angled near apex; apex of hind tibia on inner surface without heavy, flattened short setae; small close punctures on dorsal surface of propodeum adjacent to median cuneate space, larger and more scattered elsewhere and contiguous along hind margin; posterior surface of propodeum with confluent to subconfluent pits.

Disk of first tergum not ridged anteriorly; last tergum shagreened on apical fourth.

PARATYPES.—2, same label data as holotype (USNM). One paratype has been placed in the National Museums of Sri Lanka (Colombo).

The paratypes are 11.2 and 13.0 mm long and agree in all essential details with the holotype.

This peculiar subfamily with highly modified, wingless, antlike females and slender, winged males is represented in Sri Lanka by Karlissa Krombein with a single species, typical Methocha Latreille with three species, and Methocha subgenus Dryinopsis Brues with four species. Most species are known at present only from Sri Lanka, but M. (M.) litoralis, new species, occurs also on the east coast of South India.

So far as known all species of Methocha parasitize the larvae of cicindelid beetles dwelling in perpendicular burrows in the ground. Adlerz (1903, 1905) was the first to observe that the female Methocha approaches the entrance to the tiger beetle burrow, allows the beetle larva to clasp its mandibles around the constricted part of her thorax, and then paralyzes the larva by stinging it in the neck. Subsequently, the larva is dragged to the bottom of the burrow, and the wasp deposits an egg on the venter of the abdomen. The wasp then plugs the cell and fills the top part of the burrow with soil.

The host of Karlissa is unknown, but almost certainly it is the larva of one of the arboreal cicindelids which dwell in cavities in twigs and branches. The single known female of Karlissa was crawling on the trunk of a tree nearly a meter above the ground; an adult flightless cicindelid, Tricondyla coriacea Chevrolat, was captured elsewhere on the same tree. Shelford (1905, 1907) described the larva and its burrow of Neocollyris emarginata (Dejean), another arboreal cicindelid from Java. He surmised that the adult female Neocollyris oviposited through the woody outer tissue of the coffee twig into the central pith. When the egg hatched, the young larva excavated a burrow in the pith with an opening to the outside through the woody tissue. The mouth of the burrow was countersunk, and Shelford opined that the lower surface of the Neocollyris head completely plugged the burrow with its mandibles protruding into the countersunk area. Several taxa of Neocollyris occur in Sri Lanka. If the burrows of all genera of arboreal cicindelids are of similar construction, this may account for the remarkable mandibular development of female Karlissa (cf. Figures 22, 25). The two teeth at the apex of each mandible could be applied to the anterior margin of the cicindelid head in such a way that the head could be pried upward, thus exposing the beetle's neck to the wasp's sting.

Most of the Methocha males were captured in Malaise traps and were observed very infrequently around foliage or on the ground. We noted males entering traps as early as 6 A.M. at China Bay, Trincomalee, and one was attracted to an ultra-violet light trap. Some males entered traps later on cooler, windier days. Females were found crawling on the ground, usually in the vicinity of tiger beetle burrows. We noted mating or attempted mating three times by M. litoralis in the intertidal zone at Pesalai beach between 9:30 A.M. and noon.

Females were active during the day in partially or wholly shaded areas, but activity was severely limited in sparsely vegetated areas subject to intense sunlight. An exception to this was where the ground was damp, as in the intertidal habitat of M. litoralis. One damana (small open, sparsely vegetated area) across the Moderagam Aru near Kokmotte Bungalow, Wilpattu National Park, was inhabited by a small population of M. (M.) heveli, new species. On 24 May 1976 we reached the damana at 7:40 A.M. and captured two females on the bare gound at 7:45 and 7:55 A.M.; the ground by then was apparently too hot for further activity. Late in the afternoon females were again active, and we collected four females between 5:20 and 6:20 P.M. On the next day we reached the damana at 6:30 A.M. and collected five females between 6:35 and 7:11 A.M. We may have collected all of the adult females by that time, for we found none active between 5:10 and 6:25 P.M. We set small Malaise traps among shrubbery on the periphery of the damana but did not collect any males.

We followed Methocha females for lengthy periods at several locations but were unable to obtain a great deal of information. Our most successful observations were made at Pannika Villu, Wilpattu National Park, on the sand near the edge of the large villu (pond) on 1 November 1977. At 8:15 A.M., P.B. Karunaratne noted a small female of M. (Dryinopsis) taprobane, new species (11177 A; my code number, signifying month, day, and year), struggling with a tiger beetle larva at the burrow entrance of the latter. It appeared that the tiger beetle had grasped the wasp which allowed itself to be pulled into the burrow. The wasp came out almost immediately. It then walked around the burrow vicinity for more than five minutes. It went into the burrow at 8:16 A.M. and finally emerged at 8:37 A.M. Then it began to take in a grain of sand at a time. After several such trips we captured the wasp and excavated the burrow. The diameter of the perpendicular burrow was 2 mm at the entrance, and it narrowed to 1 mm farther down. At a depth of 42 mm there was a narrow, lump of dry sand. The entire burrow length was 78 mm, and the beetle larva was at the bottom with its head upward. It had a small egg on the venter of the abdomen opposite the dorsal hump. The egg was covered with a few grains of dry sand. The sand in which the burrow was excavated was very damp immediately below the surface. We put the larva in a cell in damp sand in a pill box for rearing. The wasp larva matured and spun an ovoid cocoon of delicate silk 5.5 mm long. Sand grains and chitinous parts of the host larva adhered to the outer surface of the cocoon. The adult wasp escaped when it eclosed but was probably a female.

At Ekgal Aru Reservoir on 22 February 1977, P.B. Karunaratne observed another small female M. (D.) taprobane (22277 A) on the sunny hard-packed earth of the drive near the Wildlife Department Circuit Bungalow. The wasp was plugging the burrow of a cicindelid larva and had filled the burrow to within 2 mm of the surface when we captured it. The plug was 5 mm thick of compacted earth. The next 45 mm of the burrow was empty, then there was a soft compacted thin plug directly on top of the head of cicindelid larva. The larva was in a nearly vertical cell at the bottom at a depth of 55 mm. We could find no egg on the larva, and it could not have been dislodged, because the excavation was made very carefully. We placed the beetle larva in a tin ointment box in damp soil, but no parasite developed.

We made a few observations on a small number of M. (M.) ubiquita, new species, females at Thawalamtenne on 18 February 1977. This was a flat area at mile post 30 on the Kandy-Mahiyangana Road. The locality had very low vegetation consisting mostly of grasses and prostrate broader leaved plants with occasional shrubs. The Methocha could not have been a very effective parasite, judged from the relatively small number of females compared with the numerous cicindelid burrows. At 10:12 A.M., I watched a female M. ubiquita (21877 A) on a bare spot in the meadow. In a minute it came to a spot that may have marked the plugged burrow of a small cicindelid larva. She began to burrow vertically, removing small grains of soil or sand 1–2 mm from entrance. In three minutes the burrow went downward the length of her body. She continued to back out of the burrow, sometimes pushing the soil behind her with her hind legs, sometimes carrying a grain or two out in her mandibles. This excavation went on till 10:25 A.M. At 10:38 A.M., I probed the burrow with a grass stem to a depth of 3/4 inches, but there was no reaction. We dug the burrow at 10:45 A.M. and found the Methocha about an inch below the surface with a plug of soil above her, and she was still digging. We did not find a beetle larva when we excavated deeper.

P.B. Karunaratne followed another M. ubiquita female (21877 B) for an hour-and-a-quarter. At about 10:45 A.M. she entered a large cicindelid burrow but was scared off by the larva in about half a minute. We dug up the burrow and found the beetle larva at a depth of 10 cm in rather heavy loam soil. There was no wasp egg on it.

At 1 P.M., D.W. Balasooriya found another M. ubiquita female (21877 C) digging as recorded above for 21877 A. She abandoned the burrow in a few minutes and started searching elsewhere. The burrow was only 2.5 cm long, and there was no sign of a beetle larva. This digging activity by 21877 A and C is certainly very puzzling, for there was no sign of a beetle larva in either case.

Several of the M. ubiquita females captured at Thawalamtenne had lost part of or all of their antennae. Quite likely these may have been amputated by a cicindelid larva when the Methocha probed the burrow.

Specific hosts are unknown for any of the Ceylonese Methochinae, but it is most unlikely that any of them are host specific. I believe that methochine females are highly opportunistic and will prey successfully upon any species of ground-dwelling or arboreal tiger beetle, provided that the host larva is neither too small nor too large. During my field work we collected Cicindelidae at every locality where they occurred. This enables me to suggest putative hosts for Ceylonese Methochinae as follows:

M. (M.) litoralis, new species—Cicindela biramosa Fabricius, C. distinguenda Dejean, C. sumatrensis Herbst

M. (M.) heveli, new species—Cicindela cancellata Dejean, C. ceylonensis ceylonensis W. Horn, C. c. diversa W. Horn, C. haemorrhoidalis Wiedemann, C. sexpunctata Fabricius, C. sumatrensis

M. (M.) ubiquita, new species—C. biramosa, C. cancellata, C. catena Fabricius, C. ceylonensis diversa, C. discrepans Walker, C. distinguenda, C. dormeri W. Horn, C. haemorrhoidalis, C. labioaenea W. Horn, C. sexpunctata Fabricius, C. sumatrensis, C. undulata Dejean, Prothyma paradoxa W. Horn

M. (D.) taprobane, new species—C. cancellata, C. c. ceylonensis, C. c. diversa, C. discrepans, C. distinguenda, C. dormeri, C. haemorrhoidalis, C. labioaenea, C. lacunosa Putzeys, C. sexpunctata, C. sumatrensis, C. undulata, P. paradoxa

M. (D.) kandyensis, new species—C. cancellata, C. c. diversa, C. discrepans, C. distinguenda, C. dormeri, C. labioaenea, C. lacunosa

M. (D.) ceylonica, new species—C. biramosa, C. cancellata, C. c. diversa, C. discrepans, C. distinguenda, C. dormeri, C. labioaenea, C. lacunosa

M. (D.) anomala, new species—C. cancellata, C. c. diversa. C. discrepans, C. distinguenda, C. dormeri, C. labioaenea, C. lacunosa Karlissa rugosa—Tricondyla coriacea Chevrolat, ?Neocollyris species.
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bibliographic citation
Krombein, Karl V. 1982. "Biosystematic Studies of Ceylonese Wasps, IX: A Monograph of the Tiphiidae (Hymenoptera: Vespoidea)." Smithsonian Contributions to Zoology. 1-121. https://doi.org/10.5479/si.00810282.374