LAYING AN EGG. After digging a burrow and a nest chamber at its end, hunting, paralyzing and returning to the burrow with one or two cicadas and positioning them in the nest chamber, the female wasp lays a 4-5 mm long egg on a cicada. She always lays the egg on the ventral thorax under the left or right second leg. Fabre also noted the extreme constancy of egg placement on the prey of several French sphecids and ascribed it to the necessity of keeping the egg and young larva safe from the occasional twitching of the paralyzed prey's legs and mouthparts. The picture on the right shows an egg laid on a cicada placed in an artificial burrow by a wild cicada-killer. As noted on the previous page, a female spends about 45 minutes laying an egg and closing the nest chamber with the spoils from the digging of a new nest chamber; then she hunts again.

HATCHING. The egg begins to develop soon after it is laid and, in the laboratory at 18-24 degrees centigrade, the larvae complete their growth and are ready to spin a cocoon in 5-8 days. The picture on the left is of a young larva which has just completed its first molt and is ready to chew a hole in the arthrodial membrane of the cicada's second coxa. Having gained entry into the cicada's body, the larva extends its head into the cicada and begins to eat its internal organs. Fabre notes that the developing wasp larvae of French sphecids spare the prey's nervous system as they eat; presumably this allows the prey to live longer and not spoil, a condition which often kills the larva, as shown in the picture on the right. The pictures below show a series of stages in the continued development of a larva over a six-day period in the lab (the white paper scale bar is 3 mm wide in each picture). On the far right are shown male and female larvae (their heads are down in this picture). The male larva was given two paralyzed cicadas on which to feed, but it ate only one, while the female larva ate both of the cicadas made available to it.

While they are eating their cicadas (524 KB Quicktime movie of feeding) the larvae make interesting peristaltic movements of their bodies, a process which may help distribute nutrients thoroughout their body cavities and help to bring wastes to the excretory structures. This peristalsis is shown here in a 224 KB QuickTime movie; it was also noted in French sphecid larvae over 100 years ago by Fabre.

SPINNING A COCOON. In the wild, after the larva finishes eating, it begins to spin a cocoon. The glass culture dishes in which my larvae were reared were not suitable for cocoon spinning and the larvae spent much time moving along the bottom of the dish, perhaps looking for something resembling the tactile sensations of the spherical earthen nest chamber in which they normally develop. A substitute for the tactile sensations of a nest chamber was provided to one larva in the form of a 2-cm high paper cylinder of a 3-cm diameter. This larva began spinning a cocoon (here's a 1.1 MB Quicktime movie of it beginning to weave) and appeared to successfully complete it. However, the larva died and the cocoon was very thin and did not appear normal, lacking what appears to be the mud coating and several "vents" of a normal cocoon. The picture on the left below shows this cocoon dissected to reveal the position of the larva inside it; the other two pictures below show ventral and lateral views of a male wasp which was nearly ready to hatch.

HATCHING. Larvae overwinter in diapause and pupate in the spring. Using cocoons obtained from the trap nests shown on the bottom of the preceeding page, I have begun to study the factors controlling the timing of hatching. Very preliminary data on two cocoons point to ground temperature as one of the cues. So far I have only had two of four wasp cocoons overwinter and hatch in the lab. The cocoons were taken down to a temperature of five degrees centigrade in three-degree "steps" lasting 5-7 days each in a laboratory incubator, held at five degrees over the winter, and their temperature was raised at three-degree intervals (lasting 3 to 7 days each; one began warming on 2/16/92 and the other on 3/13/92). These two male wasps hatched 108 and 95 days, respectively, after the temperature increase had begun.

In middle July through middle August at Lafayette developing wasps chew the tops off of their cocoons and emerge. A newly emerged male is shown in the picture on the right. This male hatched from a lab-reared cocoon 108 days after it began warming from 5 degrees centigrade to room temperature in the experment mentioned in the paragraph above; note that its antennae are much shorter than normal. On emerging the wasps defecate a large amount of a white, pasty meconium which is probably rich in urates and other water-saving nitrogenous wastes; this can be seen in the picture. After hatching, the larvae dig vertically from their nest chambers, reach the soil surface and emerge to begin their brief lives above ground.