Is there enough circumstantial evidence as to the plausibility of T. limbatus
life cycle and corresponding ID?
I would be happy to send adults or larvae to interested persons.
I will try to collect pupae in cocoons, maybe April - June?
Adults of Trigonorhinus limbatus
, documented on Sneezeweed, Helenium autumnale
, and larvae, perhaps T. limbatus
, feeding on Sneezeweed
Click photo for more
Partial life cycle: larva in cocoon and adult reared (from another cocoon)
Click photo for more
BG Info: Trigonorhinus limbatus
Food “T. l. limbatus feeds on pollen of various composites, especially Helenium (sneezeweed), Coreopsis, and some similar daisy-like flowers, and the larvae bore in the flower receptacle and stem. (Barry Valentine, pers. comm.)”
Identification: of the larva
Rearing: in order to see the larva in a tightly woven cocoon, the cocoon must be cut/torn open, sometimes, darn, squishing the larva. But even if the larva is live, intact, and well, can it really be expected to have the energy to re-weave a cocoon AND emerge as an adult? Therefore one specific larva tied to a resulting adult is difficult. Hence there are a couple of pieces missing in these partial life cycles.
However, sometimes incomplete and unsuccessful rearings can help and in this case they offer a bit more information.
In checking the various rearing vials from Sneezeweed collected in February 2018, again found larvae (dead) in cocoons on the surface of the receptacle, but also one larva (dead) in a receptacle and an adult (dead), just poking out from a cocoon.
It is somewhat difficult to differentiate the cocoon, woven on the surface of the receptacle, from the surrounding plant material. Larvae found in the fall are in the flowers only later must they feed in the receptacle. They then weave their cocoons on the surface of the receptacle, perhaps because there is a lot more plant parts/debris to weave into the cocoon.
There is also a lep larva found in/on Sneezeweed. It’s cocoon is on the surface of the receptacle but made differently for that of the beetle. The plant debris is of finer bits and pieces.