Sphex funerarius Gussakovskij 1934

Sphex obscurus (Fabricius)

Sphex hirtipes Fabricius, 1793, whose type depository is unknown, was listed (Vecht, 1961:32) as a questionable senior synonym of S. obscurus. I do not believe, however, that this synonymy is correct because Fabricius described S. hirtipes as being as large as S. ichneumoneus (Linnaeus), a much larger species than S. obscurus.

This is the smallest species of Sphex (, 12–17 mm long) known from Sri Lanka. In addition to its size, it is easily recognized by the black body and appendages, strongly yellow wings except apices, and the dense, appressed, silvery vestiture on the clypeus and propodeum. It has been collected at only a few localities, mostly in the Dry Zone, although it occurs commonly in the Colombo area in the Wet Zone. It is found in open areas with herbaceous vegetation from sea level to a couple of hundred meters in elevation, and with average annual rainfall of 1500 to 2600 mm. Bohart and Menke (1976:115) noted that it occurs also in India.

COLLECTION LOCATIONS AND DATES.—NORTH CENTRAL PROVINCE. Anuradhapura District: Padaviya, 18–19 May.

EASTERN PROVINCE. Trincomalee District: China Bay Ridge Bungalow, Trincomalee, 13–17 May, 24–25 Jul. Amparai District: Lahugala Sanctuary, 13–14 Jun.

WESTERN PROVINCE. Colombo District: Colombo, 17–23 Feb, 23 Jun, 8 Jul, 29, 30 Oct; Ratmalana, near airport, 13 and 19–21 Jan, 15–17 Feb, 8 May, 6 Jun, 29 Sep.

Dates of capture in and near Colombo suggest that S. obscurus may breed throughout the year under favorable conditions. All of our behavioral observations were made during January and February 1975 in a field across the airstrip from the Zoo Farm at Ratmalana.

FIELD OBSERVATIONS.—The soil had areas of both sand and sandy loam and was rather sparsely vegetated. Bembix orientalis Handlirsch and B. borrei Handlirsch were also nesting commonly in the field. We revisited this site several times in later years and captured a few specimens of S. obscurus in May, June, and September. We did not observe any nesting during these visits because the field had become densely overgrown with vegetation.

The following account is based on notes 11975 A, C, E, and F; 12175 A and B; and 21575 B, F, H–M, Q, and R. We observed nesting first on 19 January, excavated two of the nests on that date, and marked two that we dug up two days later. We noted ten nests on 15 February, dug up four of them on that date, and marked six that we dug up two days later.

Nest Construction: The nests were begun on bare, flat ground, usually in sand or sandy loam, and frequently adjacent to a grass tuft or small plant. The burrows were constructed at angles ranging from 45° to the horizontal to perpendicular and had a diameter of about 10 mm. The wasp brought the sandy soil to the surface between her head and forelegs, and then scraped it backwards beneath her to form a spoil heap. The spoil heap was low, flat, rounded, and eventually covered an area as much as 5 cm wide and 5 cm long behind the burrow entrance. When a wasp first began a nest she dug in the burrow for only 8–10 seconds before backing out with a load of soil and raking the soil backward over the surface for a few seconds. As the burrow lengthened she spent up to 30 seconds digging and then raked the soil backward beneath her to enlarge the spoil heap.

I was unable to ascertain the time required to dig a burrow and prepare the cell, but it must be lengthy. I saw one female (21575 B) enter a burrow at 0913 on 15 February, emerge a minute later, leave the burrow open, make a brief orientation flight, and then leave. She returned half a minute later, flew around for a few seconds, reentered the burrow and began to excavate, but was disturbed by us and flew off in a few seconds. She returned at 0920, entered the burrow, came out, and then went back inside several seconds later. She then began to excavate sandy loam as detailed above. I spent the next three hours visiting a series of nests, but returned occasionally and noted that 21575 B was still excavating soil at 0937, 0955, 1006, 1100, and 1125. She was not there at 1140 but had left the burrow entrance open, suggesting that the nest had not been completed. At 1200 she returned, entered the nest and then came out, and repeated this sequence several times until I frightened her. The burrow was still open at 1245 and 1535 but the wasp was not there either time. She was completing a final closure of the nest between 1755 and 1815 on 17 February. The fully stocked cell contained a half grown wasp larva and the remains or complete specimens of four prey.

P. Fernando observed another female digging in a burrow at 1100 on 21 January. She continued digging intermittently until 1400, when she flew away leaving the entrance open. We dug up this nest at 1745 and noted that the burrow was perpendicular and ended at a depth of 7.5 cm where the wasp encountered hard-packed soil and abandoned the nest. The lower 5 cm of the burrow was in damp sand. We noted three other burrows that had been abandoned at depths ranging from 2.5 to 10 cm because the wasps came to an impervious stratum. The top 3 cm or so of two burrows had been filled loosely with sand, and the third burrow was left open.

Temporary Nest Closure: On 19 January at 1340 I found wasp 11975 C making a temporary closure. She raked sand from the spoil heap backward beneath her into the burrow entrance, then turned around, entered the burrow headfirst presumably to compact the sand with her head. The plug must have been fairly deep for she was out of sight while inside the burrow. She remained inside about 10 seconds, then emerged and spent 5 seconds throwing sand backward into the entrance. She continued this sequence for 18 minutes, gradually raking the sand from farther and farther away from the entrance and throwing it in the general direction of the burrow. Then she came closer to the entrance, threw the sand inside and entered the burrow to compact it. At 1358 she left the area, leaving the upper 3.2 cm of the burrow empty. She had not returned to the nest when we excavated it at 1640. The burrow was at an angle of 70°, was 10 cm long, and the bottom 7 cm had been plugged with soil. This was just a temporary closure because the cell contained only two prey and neither bore an egg although one should have been laid on the first prey brought in.

I observed a second female (21575 R) bringing a prey into her nest at 1427 on 15 February. She remained inside the nest with the grasshopper for 20 minutes, emerged headfirst, ran about for a few seconds, re-entered the burrow, came out almost immediately, flew off and returned at 1449 and went inside the burrow. She came out almost immediately and proceeded to make a temporary closure as described above. We dug up this nest at 1530 after the wasp had left and found the upper 25 cm empty, then a plug of mixed dry and wet sand 2.5 cm thick along the vertical axis, and finally a horizontal plug for 7.5 cm to the cell. The latter contained a single prey bearing the wasp egg.

Final Nest Closure: I first saw wasp 21575 Q at 1350 on 15 February when she was filling in her burrow in the manner described in “Temporary Nest Closure” (above). She completed filling the burrow at 1445 after some interruptions, and then began to scrape sand from the shallow depression, 15 cm wide, in which the nest was made in order to make the surface more nearly level. She stopped this process every few minutes to fly onto one of the small adjacent plants to clean her antennae and legs, and perhaps to inspect the area to ascertain whether the nest entrance was adequately concealed. She completed distributing the sand over an area of several square centimeters by 1504, and even dragged in small pebbles and placed them randomly around the entrance. We dug up the nest and found that the entire burrow, 18 cm long, was plugged. The cell had been completely provisioned and contained a large wasp larva, one whole prey, a partly consumed prey, and fragments of two other prey.

P.B. Karunaratne observed final closure of the nest by 21575 B on 17 February. I had noted nest excavation by this female on the 15th. The nest entrance was open at 1630 on the 17th, and still open at 1700. However, by 1755 the burrow had been filled except for a small depression at the top. The wasp returned, filled the depression with loose sand, concealed the entrance with a few bits of dried leaves, and left the area at 1817. The entire length of the burrow was filled with compacted earth to a depth of 17.5 cm. The cell was about 3.7 cm from the burrow axis and contained a half grown wasp larva and four prey (two whole specimens and fragments of two others).

We observed a third female (21575 I) on 15 February making a final closure as described above for 21575 Q. We dug this nest before the wasp had plugged the upper 3.7 cm, and found the burrow firmly plugged with earth to a depth of 15 cm. The cell contained a wasp egg almost ready to hatch and six prey.

On 15 February at 1140 I observed another female (21575 K) excavating her nest. We marked the location and returned on the 17th. There was no trace of a nest at 1645, and the area around the entrance was covered with loose sand and scattered leaf fragments. The burrow was firmly plugged with earth to a depth of 25 cm. The cell contained a wasp egg and four prey.

Nests 21575 I and K described above show clearly that S. obscurus is a mass provisioning wasp, i.e., that an egg is laid on the first prey and that the cell is completely provisioned before the egg hatches. However, mass provisioning is occasionally delayed because of weather, lack of prey, or other reasons, so that the egg hatches and the larva begins feeding before the cell is completely provisioned. It appears that nests 21575 Q and B described above are examples of delayed mass provisioning and not of progressive provisioning as is true in S. subtruncatus krombeini Vecht.

Nest Dimensions: The burrows ranged from perpendicular to an angle of 45° to the horizontal, had a diameter of about 10 mm and varied in length from 10 to 28 cm. Occasionally the burrow curved around a root or other obstruction, but then continued downward along the same axis. Invariably, the cells were in damp sand, horizontal and constructed at the end of the burrow, although occasionally they were made at the end of a short horizontal section of the burrow. The cells were usually ovoidal and 1.3 to 2.5 cm long and 1 cm wide, but occasionally they were almost spherical.

Prey Identification: This population of Sphex obscurus preyed upon three species of long-horned grasshoppers, Conocephalus (Tettigoniidae, Conocephalinae). They used both sexes of nymphs and adults of C. maculatus (Le Guillou) and the brachypterous C. signatus Redtenbacher, and only one specimen of C. longipennis (Haan). We did not observe prey hunting and capture, but presumably the wasps hunted for their prey in the rather dense herbaceous vegetation surrounding the sparsely vegetated, sandy loam field where nesting occurred.

I observed prey transport and storage only once. The female (21575 R) flew in with her paralyzed prey at 1427 on 15 February. She set the grasshopper on the ground with its head near the entrance, entered the burrow headfirst, came to the entrance headfirst, reached out to grasp the prey and dragged it into the nest.

Fully stored cells contained 4 to 6 prey (average 4.6), usually a mixture of two species and both sexes of nymphs and adults. Altogether we recovered 11 C. maculatus (4 nymphs, 5 females, 2 males), 14 C. signatus (7 nymphs, 4 females, 3 males), only one female C. longipennis, and fragments of one specimen that could be identified only to the genus Conocephalus. The prey ranged from 7 to 21 mm in length, but the inedible tegmina extend well beyond the abdomen, so that total body length available to the wasp larva usually did not exceed 11 mm exclusive of the inedible ovipositor.

Immature Stages: Three wasp eggs were recovered from nests of 21575 I, K, and R. Unfortunately none remained attached to the prey. It is presumed that the wasp would have laid the egg transversely on the thoracic sternum of the first prey brought into the cell, with the cephalic end glued between the fore and mid coxae. The eggs were slightly curved, 3.0 mm long, and 0.5–0.6 mm wide. No data were obtained on duration of the egg stage, but presumably the egg hatched within two days after oviposition.

We opened two nests, 11975 C and 12175 B, each of which contained two prey but no egg. It is possible that in each case the egg may have been dislodged during our excavation of the nest for the egg does not seem to be attached firmly to the prey.

We obtained half- to full-grown larvae from a number of cells but did not try to rear any. I presume that the wasp larva reaches maturity within 3 to 4 days after hatching and then spins a cocoon from which an adult will emerge in several weeks.

Male Activity: We observed no activity by males either during nest construction or during prey transport. Perhaps in this species mating precedes any nesting activity by females.

Parasites: The only parasites I noted were three Miltogramminae (Sarcophagidae) on 15 February. The first was a female of Protomiltogramma seniorwhitei (Verves), which perched on a grass stem near the burrow while wasp 21575 H was digging its nest at 1025. Later in the afternoon at 1425 wasp 21575 R carrying prey flew toward its nest, followed closely by two miltogrammine flies. I captured one male, 5.5 mm long, as it alighted on the ground near the entrance. It too was a specimen of P. seniorwhitei.

Inasmuch as Sphex obscurus is not a progressive provisioner as is S. subtruncatus krombeini Vecht, it is probable that parasitism of the nest by P. seniorwhitei would result in the death of the wasp larva from lack of food. A wasp that practices progressive provisioning would bring in enough prey so that both the wasp and fly larvae would reach maturity as I found in S. subtruncatus krombeini.

Sphex funerarius, the golden digger wasp, is a species of digger wasp of the family Sphecidae.