I have a Malaise trap set up in woods behind the Penn State Arboretum to capture fresh Conostigmus specimens for DNA. Today I went through the first week’s sample and found 6 Aphanogmus, 4 Ceraphron, 1 female Lagynodes….and no Conostigmus. Of course.
But wait a minute– a female Lagynodes, in a Malaise trap? The females of this genus have no wings, and are thought to live in the ground. So what would a tiny, wingless wasp like this be doing in a trap intended for flying insects?
It is possible that female Lagynodes are phoretic, climbing onto larger insects and catching a ride from them. This could be a means of dispersal for a tiny wasp with no wings, but there is probably more to this behavior than wanderlust.
Parasitoid wasp hitchhikers may cling to larger female insects and wait for them to lay their eggs. At this point, the hitchhikers can then climb off and lay their own eggs on or inside the eggs laid by their ride. Thus, the female parasitoid can find hosts for her offspring to parasitize, all without having to fly herself.
But how does such a small wasp catch a ride as a hitchhiker? (They can’t just stick out a thumb by the side of the road and wait.)
The answer is to go where the other insects go. Female Lagynodes could climb up plants and sit on flowers, waiting for whatever insect they parasitize to come by. If they climb onto a male of their target species, they could wait for the male to mate and use that opportunity to jump ship and transfer to the female. After then, it’s only a matter of time waiting for the female to lay eggs that can then be parasitized.
So what insect could female Lagynodes be phoretic on? Unfortunately, there are no host records for Lagynodes. We typically find females in leaf litter or ground-related samples, but Dessart 1990 did report that for the species Lagynodes luciae, males were found in pitfall traps and females were found in flight interception traps.
The female Lagynodes I found was floating freely in my Malaise sample among many other insects, from Phoridae (Diptera) to Braconidae (Hymenoptera) to Noctuidae (Lepidoptera). Since it was not found clinging to anything, there’s no telling what it is phoretic on, if it is phoretic. What do you think?
Dessart, P. (1990). À propos de Lagynodinae nouveaux ou peu connus. (Hym. Ceraphronoidea Megaspilidae) 1) Lagynodes luciae n. sp., première espèce de la sous-famille découverte en Afrique noire et 2) Lagynodes obscuriceps Dessart, 1981: première espèce connue à mâle trimorphe. Bulletin de l’Institut Royal Des Sciences Naturelles de Belgique, Entomologie 60, 77–83.