Sitona lineatus
A very common weevil and one we see within the Garden frequently. They are good fun to observe as they plod about in that weevil-like fashion. Often appearing almost inquisitive, but more often very quick to hide/disappear.
Adults feed on the leaves of peas and beans, whilst the larvae do likewise on the roots of the same plants. Some websites state they have little negative impact on the food plant and are therefore not usually considered a pest within the UK, although in some countries it can become a serious threat to crops.
The adults you see in spring have likely overwintered down amongst the grass / clover stems and mate in spring, producing eggs up until mid-summer when the current generation dies off. The new generation then gets on with the business of feeding, the larvae burrowing into the soil looking for the roots of its food plant. Several weeks later and the much larger larvae pupate and a couple of weeks later the next generation of adults emerge. Quickly getting down to the business of feeding before they too consider finding a good spot to see the winter through before mating begins afresh the following spring.
We don’t actually have any legumes growing in the Garden. So assume the adults are popping in on their way to potential food sources elsewhere.
Identification can never be certain from observations in the field as other species of Sitona are similar and microscopic examination is needed for absolute confirmation. However, S. lineatus is the most common species, and the stripes and blunt, almost rectangular snout are indicative of this species.
DC: 07.05.2024
Wildlife Garden 