FEMALES HATCH AND ARE MATED. Females begin emerging onto the lek one to two weeks after the first males appear, late in July in Easton, PA. I have preliminary results which indicate that virgin females emit a pheromone which attracts males to them: when placed on an active lek, screen mesh bags containing virgin females attracted many more males than bags containing males or empty bags (the "male visit ratios" are 8:2:1, respectively for two trials). Here's a picture of the experimental setup. I have seen several mating pairs as they flew away from leks with no other males present, so I presume that the first male which finds the female gets to mate with her if no other males interfere. Lin (1966) has described copulation in the cicada-killer, but he missed the precopulatory behavior noted under "Foreplay" below. As he notes, cicada-killers are the first sphecids to be observed flying united.

Given that there are often several males on a lek when a virgin female emerges, one might think that they would compete to be her mate and sometimes this is the case. I have seen balls of up to 8 wasps on three different leks; these are composed of one female and several males struggling to mate with her, as in the picture on the left. I call such groups of wasps "scrums" and the wasps in them are sometimes gripping each other so tenaciously than the wasps on the inside can't move at all. Occasionally a mating pair will be visited by one or more males which will mount and try to mate with the female, despite the fact that she is already in copulo with another male. The picture below on the right is of such a group. The male on the female's back is shaking her head back and forth with his forelegs (see "Foreplay" below) and the male on his back is shaking his head. The female in the picture eventually fell off of the wall of the aquarium and a scrum formed on the aquarium floor. Later the two unsuccessful males walked away from the still-copulating pair; one of the departing males was still mounted on the other's back and still shaking the walking male's head.

FOREPLAY. Before mating, a male mounts the female and shakes her head back and forth with his front legs and taps the female's antennae with his own. Although described by Reinhard in 1929 (The Wichery of Wasps, Century Press, NY, p. 41), this behavior is not mentioned in the recent literature, even by Lin, who has published extensively on mating in Sphecius. One instance of similar male precopulatory behavior has been reported for Sphecius grandis by Alcock (1975). It has recently been shown that the antennae of male ichneumonid wasps (and, presumably, males of all other wasp families) have glands called tyloids which make a sex pheromone that puts the female in a mood to mate when it is rubbed on her antennae (Bin et al., 1999).

This precopulatory behavior provides the female with ample opportunity to assess the male's weight (she's carrying him) and his strength (he's shaking her head; both activities are shown in the picture at the top of the page and in a 296 KB Quicktime movie available here). If competition between lek males for access to virgin females is common, then one might think that larger or more aggressive males would have an advantage. Joe Coelho and I have conducted experiments to see if this is the case. We have published a paper (J. Insect Behavior 14: 345-351) presenting data which show that, when several males are competing for the same female in the wild, the one which manages to mate with her has a significantly larger percentage of body mass as flight muscle (thorax mass, actually), perhaps indicating a higher degree of fitness in aerial fighting and a better ability to keep other males off of a given area of the lek when virgin females are emerging. However, in laboratory experiments conducted with five males and one virgin female placed in a 5-gallon aquarium, we found that smaller males had a significant advantage in mating, perhaps because they were better able to compete in the scrums which frequently occurred in these experiments.

In situations where a single male is present on the lek, newly-hatched females may not be able to afford to be picky if they wish to mate. Given the vagaries of male and female hatching and male presence on the lek, there are probably many cases when there is only one male available to mate with females which have hatched, emerged and are ready to mate. I simulated this situation in the lab by offering the smallest male wasp I have captured (198 mg, "Tiny Tim") to three different virgin females at one-day intervals. Tiny Tim was readily accepted by all of the females and mounted and mated each one within the first minute of their time together in the container. So, at least in the laboratory and when only one male is available, "It's not the size of the wand that puts the rabbit in the hat, but the skill of the magician." Tiny Tim is shown hanging in there with a small female in the picture of the nuptual couple and two hopeful suitors on the right. In the picture on the left a similar mating in the wild is shown. My thanks to Andrew in Mercer County, NJ, for this picture.

MATING BEHAVIOR DISSECTED. Mating in cicada-killers has several behavioral components which always occur in the order shown below. I have measured the durations of these components in 7 matings observed in the lab in 1999. The behaviors and their durations are as follows:

• Time for male to mount female after his introduction into the mating container: 59 +/- 23 seconds (S.E.M.)
• Time male spent shaking female's head and tapping her antennae with his own: 53 +/- 25 seconds
• Time male spent trying to insert his genitalia into the female: 6 +/- 1 seconds (Here's a 404 KB Quicktime movie of intromission)
• Time in copulo with male on female's back: 20 +/- 10 seconds
• Time male spent trying to walk or fly while tail-to-tail in copulo with female: 24 +/- 10 seconds
• Time spent quietly tail-to-tail in copulo with female: 62.5 +/- 11.3 minutes. NOTE: one male tried to fly or walk three times after quieting down while in copulo; this mating lasted only 36.5 minutes and was the shortest time spent in copulo.
• Total time spent from male mounting to end of copulation: 71.4 +/- 7.9 minutes
• Two of seven males attempted to remount their females and were rebuffed by them.

From these observations we can see that males waste little time attempting to mate with a virgin female, that they are readily accepted by the females and that the vast majority of time in mating is spent quietly in copulo.The long time of quiet copulation may be an example of males guarding their mates from copulation with other males until they have filled their spermathecae with the male's sperm and are no longer receptive to other males' attempts at mating. This kind of "mate-guarding" behavior is known in many other insects. The penes of many male insects lock onto ridges in the female's reproductive tract and this keeps the male and female locked together if other males find the mating pair or if the female struggles to free herself. Presumably, the male decides when copulation will end. As noted by Lin (1966), disturbance of the pair of wasps by other males or by a human observer often results in the mating pair flying off of the lek to a quieter site, where copulation is completed. When mating pairs fly, the larger female pulls the male backwards through the air and the speed of flying is much slower than normal.

POSTCOITAL BEHAVIOR. It is well known that honeybee queens mate with several different males on their orgiastic mating flights; however this in not the case in cicada-killers. After being mated in the laboratory, and, presumably in the wild, females do not allow a second male to mate. On five different occasions in the lab I introduced a second male into the mating container after removing the male which had finished mating with a female. In every case the female raised her abdomen away from the substratum, making it difficult for the second male to mount her; each female also gave a warning "buzz" with her wings. This behavior quickly discouraged the second male from further attempts at mating. The fact that the second males all vigorously attempted to mount the recently mated females is indirect evidence for the existence of a mating pheromone which was still in the container and on the newly-mated female and which undoubtedly stimulated the second males to attempt to mate.

Finally, in mark-recapture studies, I have shown that female cicada-kilers usually leave the area where they hatched and were mated (only 2 of 20 marked and mated virgin females were seen again in 1997, as opposed to 44% of females caught and marked while looking for burrow sites). This may well be a way of ensuring outbreeding and is the opposite of what Lin (1978) found in the cicada-killers he studied for ten years at playing fields in Brooklyn, NY; his marked females returned in what appears to be large numbers (Lin presents no data) to their natal leks a week or so after hatching. Of course, Brooklyn is not noted for having large amounts of habitat suitable for cicada-killer nesting areas, so it may be that Lin's wasps used the only habitat available to them: the one in which they emerged.