A close look at an Alder spittlebug

This cold Alder Spittlebug, Aphrophora alni, sat on a rose leaf, cold and reluctant to fly, so I decided to give it a session on the white bowl, and it graciously obliged. The Alder Spittlebug is one of the largest British froghoppers (9-10 mm), so called for their - alleged - resemblance to a frog and their ability to jump. Unlike the Common Froghopper, which is smaller and on close inspection covered on fine hairs, the Alder Spittlebug has fine dark punctures and is less variable in colour. They also have a distinctive keel in the middle of the thorax, visible in the photo below. They are sap feeding insects, both nymphs and adults, and they feed on a range of plants. Adults are usually found in trees, but they descend to lower vegetation to lay eggs. 
 Froghoppers are the fastest jumping insects, outperforming fleas: they can jump up to 70 cm in the air, with an acceleration equivalent to 550 times gravity. Their hind legs - tucked underneath their wings in the photos - are powered by huge muscles in the thorax and the catapult-like jump is effected by elastic energy stored in a membrane. Another fascinating aspect of their behaviour is sound communication. Froghoppers and other small homoptera have a repertoire of vibrational drumming sounds - inaudible for us - which transmit through the substrate where they sit and that individuals use in communication. Songs can be territorial, regulating the distance between feeding individuals, or involved in attracting a mate, emitted by males and to which females respond, and they also sing as a form of fighting when two males are close together or when in distress.

More information
Burrows M (2009). Jumping performance of planthoppers (Hemiptera, Issidae). The Journal of experimental biology, 212 (17), 2844-55 PMID: 19684220 Tishechkin (2003). 

Tishechkin, D.Y. (2003). Vibrational communication in Cercopoidea and Fulgoroidea (Homoptera: Cicadina) with notes on classification of higher taxa Russian Entomology, 12, 129-181

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.