Fat lily beetle larvae

While checking the underside of my lily leaves for lily larvae I found this giant on the 22 of June. A fully developed larvae, no longer protected by its own poo, but ready to drop to the pot soil to pupate. Still haven't found any pupa, might try later in the year when I repot some congested lilies.

Larvae in a poo costume

Of all insect larvae I have come across, these have been the trickiest to spot. Red Lily Beetle adults were mating and laying eggs on my Asiatic lilies this afternoon. I was sitting next to the lilies and I was intent on spotting the larvae. It took a while. They look exactly like wet caterpillar poo. 

The bright orange eggs are laid in rows under the leaf, and when the larvae hatch they stay together and start eating the leaf where they have been born, their slimy droppings are deposited on their back, forming a faecal shield which grows in size with the larvae. The faecal shield disguises the larva, presumably helping to protect them from predators. When small, larvae fed on the underside of the leaf, leaving the upper leaf surface withered. As they grow they disperse from their siblings and they may move to the upper side of the leaf, eating the whole leaf or flowers as they grow. If they feel disturbed, they completely retreat inside their fecal shield, when they relax, their shiny black head and short legs are visible (above). The fully developed larvae drop to the soil where they make a white cocoon. There is a single generation a year, the new generation of beetles emerges and feeds before overwintering in the soil.

A string of lily beetle eggs

A cluster of young larvae - the leaf has been turned upside down to take the photo. The withered end of the leaf can be seen in the background

Chirping lily beetles

The sun shone in all its glory to end this most rainy April. Many insects came out of their temporary hiding places to dry out and enjoy the warmth. Some of these were Scarlet Lily Beetles. I wasn't sure if I had an infestation, as I had collected just a couple of adults in the last few weeks, but today I found 12, the first ones were a mating couple. As I found them I placed them in a plastic pot, and while I was carrying it I noticed a faint chirping call. I thought that there must be a nest nearby with calling chicks, but then I realized that the sound was actually coming from the pot: the disturbed Lily beetles were stridulating! when I touched them, they chirped repeatedly. You can watch this short clip of them in the pot, as I push them inside the pot, they chirp - I was trying to place the camera on the pot opening to improve the sound recording, but they kept climbing up the pot.



The first description of the stridulation of this beetle was written by the early entomologist René Antoine Ferchault de Réaumur in 1737:

when one holds it, it lets a little cry be heard, produced by the friction of its last abdominal segments against the elytra, the more one presses the elytra against the body, the louder it cries

More recent studies have confirmed this description, and also shown that stridulation is common in the Lily Beetle subfamily (Criocerinae). The stridulatory apparatus consists on a file on the last tergite - the dorsal end of the abdomen - made of microscopic parallel ribs, which are scraped by files of sharp denticles in the underside margins of the elytra. The sound is produced while the abdomen contracts, and these contractions can be amazingly rapid, up to 200 times per minute and is loud enough to be heard if the beetles are less than 30 cm from your ear. The high variability of the chirps and the situations in which they are produced suggest that this behaviour is a defence mechanism: the beetle will chirp if captured and the sound can startle the potential predator to release the beetle before swallowing it. In other beetle species chirping is used in intraspecific communication, with the lily beetle, is is yet another way of avoiding being eaten.

More information
Michael Schmitt & Dieter Traue. 1990. Morphological and Bioacoustic Aspects oî Stridulation in Criocerinae (Coleóptera, Chrysomelidae). Zool. Anz, 1990, 225: 225-240.

A beautiful pair, but not for the lilies!

This pair of Scarlet Lily Beetles, Lilioceris lilii, was mating on my Asiatic lilies a couple of days ago. These shiny leaf-eating beetles have emerged from the soil, where they overwinter, just when lily shoots and leaves are well developed. Both adults and larvae are voracious and can quickly defoliated plants. I have posted on this species before, but you can submit your records to the RHS Lily Beetle Survey, where there is more information on the species.

A red lily beetle

I spotted a handsome, bright scarlet beetle, hiding under a lily leaf. It didn't take long to identify it as the red lily beetle, Lilioceris lilii, with its long antennae and black legs and head. I took it to the white bowl and it showed two behaviours that may have helped this species expand its range from Asia to many temperate areas following horticultural Asiatic lilies: it plays dead when handled or disturbed and flies readily. The adult and larvae feed on lilies and fritillaries of many species and they can defoliate the plants very quickly. They have a single generation per year: the adults emerge in september and overwinter in the leaf litter. When the lily leaves appear the adults wake up and mate. They lay bright red eggs in lines underneath the leaves and the larvae, which are also red, disguise themselves on their own fecal matter, so that they resemble fragments of dirt.

The species was first introduced in the UK in 1943 and has recently expanded quickly in range. Now is present all over England, and parts of Wales and Scotland. Two species of parasitoids have followed the expansion of the beetle into the UK.

More information

The red Lily beetle website.