A small selection of insects that use thistles.
With the massive decline in insects and pollinators it's worth looking at one of our common native wildflower families - the Thistles.
Thistles are considered to be a plant pest where agriculture is concerned and there are even laws in France to hold people responsible for removal from their land or at least preventing them from setting seed and yet they are incredibly important for bees about which we hear so much. Creeping thistle in our fields buzzes with bees when they are in flower and a picture of a bee on a thistle was even used in a French Government brochure about “saving our bees”.
It is however an unfortunate fact that Government Departments all inevitably have their own agenda and the Department that represents the environment and conservation of wildlife is always the poor cousin that doesn’t get much say where agriculture and countryside management are concerned due to the fact that there is no obvious economic value to be obtained.
Anthidium cingulatum and Anthidium florentinum are two of the species of carder bee that are present in France. Female Carder bees use existing holes or crevices to make their nests that are lined and sealed with dense velvety hairs from the leaves of certain plants. Males patrol and guard territories where there are suitable plants for the females in the hope that they will be the one that gets to mate with them.
The Buff tailed Bumblebee is one of the commonest Bumble bees in France and usually the first to be seen in late winter / early spring. As the Latin name Bombus terrestris implies it is a species that tends to make its nest in the ground using an existing tunnel or cavity, frequently in the base of a stone wall in France where mice have created a tunnel. Colonies can contain several hundred bees and only young newly fertilised Queens over winter hibernating somewhere dry and not too cold.
The Holly blue, Ilex aquifolium, butterfly is widespread in France with two generations a year. As the name implies the caterpillars are frequently found on Holly although Bramble, Spindle, Ivy and Gorse are equally popular. There are two generations a year and they over-winter as pupa often suspended under a leaf.
Eristalis-tenax is one of the more common hoverflies in France and the larva are the rat-tailed maggots that live and develop in drainage ditches, pools around manure piles, sewage, and similar places containing water badly polluted with organic matter. The larvae leave the water to pupate and once hatched the adults feed on the nectar from a number of flowers; again the Apiaceae (or Umbelliferae) are often favoured. They mainly over winter as adults in cavities and other sheltered places.
Halictus-scabiosae is a common mining bee that nests in hardened bare or sparsely vegetated soil, footpaths or poor lawns would be typical. Females make vertical shafts with galleries to place their eggs in. It’s an interesting solitary species in so much as more than one female may share the same tunnel. The nests are susceptible to Sphecodes gibbus a cuckoo bee that puts its eggs in the solitary bees nest.
The Brown Hairstreak is the largest hairstreak in France and a species that tends to occupy the same area year after year where it is established providing its larval food plant, principally Blackthorn, is present and not over managed. They spend a lot of their time basking high up in trees. There is one generation a year which can be seen from the start of July and the species winters in the egg stage.
Andrena flavipes is one of our more common mining bees to be found in a variety of open habitats. They nest singly or more likely in congregations giving the appearance of a colony. Nests are made in clay or sandy soils in open or sparsely vegetated sunny situations. First generation can be hatched as early as the end of February in mild regions with a second generation from the end of June.
The Carpenter bee Xylocopa violacea is the largest solitary bee in Europe and despite their scary size they are really quite timid. Unusually both males and females over winter and then breed in May / June. Females make their nest in degraded old logs, dead trees and branches etc. and normally an existing hole is used. A single entry hole leads into multiple galleries into which the female lays her eggs, each one blocked in with a pellet of pollen which provides nutrition for the larva. The adults emerge in late summer.
The Swallowtail butterfly can be found in a huge range of habitats in France including in towns and cities. Caterpillars feed on many species of the Umbelliferae with carrot and fennel leaves being top of the list in gardens where they don't eat enough to cause harm. They over-winter as pupa.
Carpocoris purpureipennis is a shield bug that is usually found in natural meadows and grasslands on thistles and Apiaceae (or Umbelliferae), commonly known as the celery, carrot or parsley family.
The Map butterfly is best-known for having two distinctly different forms, levana and prorsa that represent the spring and summer generations. Spring form - levana are primarily orange in colour, giving them the appearance of a small fritillary, whereas the summer form - prorsa individuals look more like a very small White Admiral. Caterpillars feed on Stinging nettle and over-winter as pupa.
Something that is a little different and may go unnoticed but this species of gall fly requires that the thistles are left to stand overwinter.
Urophora cardui or the Canada thistle gall fly is a fruit fly which, contrary to its common name, is indigenous to France and Central Europe but is named after the host plant, the Canada or creeping thistle (Cirsium arvense),
Life Cycle: Overwintering: Urophora Cardui overwinters in the third instar, mature larva, within a stem gall on Canada thistle.
Egg Stage: One to thirty eggs are laid in stems during the warm, growing season of the plant.
Larval Stage: First instar larva stay in the egg. In the second instar eat into the stem and cause the formation of a gall (swelling). The larva grow during this time. When the insect goes to the maturation stage, the larva molt and achieve 98% of their body weight. That is their third instar. After overwintering the larva pupate and soon appear as a fly inside the gall.
Pupal Stage: The larva pupate in early spring for 24 to 35 days. They are then reddish-brown in color and stay inside the gall.
Adult Stage: Possibly oxygen stimulates the appearance of the adult fly from the gall during gall deterioration. The fly enters through a tunnel formed from the gall to the outside. This happens during June to October. Adult flies have black W-markings on their wings and are about the size of a house fly
Thistles also provide valuable nutritious food for seed eating birds in autumn and winter which is very important given the declines we have witnessed in their numbers since the intensification of agriculture. They also come in many varieties with different shapes, sizes and colours. Of course the common species aren't in any danger and it isn't being suggested that they should be tolerated or allowed to grow inappropriately but they definitely should form part of any wild areas we create.