Phratora laticollis

This small (3.7–5 mm) beetle is similar and size and coloration to other species of Phratora. Adults are typically metallic blue or green. In Europe, it is most likely to co-occur on Populus host species with two other Phratora species Phratora vitellinae and Phratora atrovirens. It is larger and more abundant than P. atrovirens and somewhat narrower in body shape than P. vitellinae. Eggs are typically laid in clutches of 8–16, arranged in rows on the underside of the host leaf. Like other Phratora species, eggs are partially covered with a crusty secretion. Larvae feed in groups in early instars (molts), and sometimes show color polymorphisms.

Phratora laticollis has a widespread distribution. In Europe, it is found in Arctic regions and the Nordic countries, the United Kingdom, Germany to Spain, Serbia and Bosnia, and Bulgaria. It is also found in China and elsewhere in Asia. Populations occur at high elevations in parts of central Europe and China.

Lühmann (1939) described the life history of a population in Germany in detail. After overwintering, adult beetles seek mid-sized trees of Populus tremula within aspen groves for feeding, oviposition, and production of the summer generation. When spring arrives, overwintered beetles spend 2–3 weeks feeding and lay up to 250 eggs on the undersides of leaves. After eggs hatched, larvae spent about 5–6 days in the first, second, and third instars before leaving the host plant and making a pupal case. After about six days, adults emerge and remain in the pupal case for an additional two days before emerging. In central Europe, this species can experience multiple generations per growing season (multivoltine), but it appears to undergo only one generation per summer in the Nordic countries or at high elevations. Overwintering was observed under the bark of fir trees near the Populus tremula stand where beetle populations had been found. Van der Laak (1982) investigated the mechanisms of cold tolerance and overwintering success in P. laticollis. These studies revealed that P. laticollis can be 'freeze-tolerant' in summer and winter. Multiple mechanisms influence cold tolerance and it varies over the year partly due to the concentration of metabolic products such as glycerol and other factors.