Picromerus bidens

Bidentate thorn bug ( Picromerus bidens )

The bidentate thorn bug or bifurcated bug ( Picromerus bidens ) is a bug from the family of stink bugs ( Pentatomidae ).

Features

The bidentate thorn bug reaches a body length of 10 to 14 millimeters. Their color is dark brown, on the neck plate it carries two red dots. The German name from the way the two sharp, black-brown spines on the sides of the pronotum. These are not yet developed in the nymphal stages. The species is airworthy.

Occurrence

The species occurs in Europe and northern Asia to Japan before. It is found in deciduous and mixed forests as well as in gardens and prefers moist locations, for example at the edge of the forest or in heath and dune landscapes where food plants of many caterpillars and beetle larvae are found.

Way of life

Development

The bidentate thorn bug is univoltine, every year there is only one generation. The females lay the eggs on the top of the leaves, where they overwinter. The larvae hatch in the spring and have five molts survive to grow until the summer to imagos can. The rate of development is dependent on the temperature and lasts up to 20 ° C under laboratory conditions just 64.5 days. Of these, responsible for the development of an ice approximately 23 days. Are the days in the period after the development of the mature animal long and the nights short, then finds the first egg-laying take place only after some time. This prevents that the young hatch too early and then have to survive the winter as nymphs without food supply. Only in southern areas where the days are shorter in the summer and where not a particularly hard winter reigns, the females begin to lay eggs the same. There the nymphs can overwinter case by case basis.

Nutrition

The bidentate thorn bug is predacious caterpillars, beetle larvae and aphids. The nymphs live on the same prey as the Imagines. On the nature nettle caterpillars of the peacock butterfly captured, for example, on the old man herbs Jakobskrautbär of the subfamily of the tiger moths. Among the beetle larvae are leaf beetles preferred prey. The choice of prey is also dependent on the seasonal availability of food. For example, it feeds in the early autumn of caterpillars of the marsh fritillary butterfly and other Melitaeinae when other prey is unavailable. Iridoid glycosides, which are in the food plants of these butterflies, eg Succisa pratensis, formed and absorbed by them shall, inter alia because of their bitter taste of the chemical defense against predators. The bidentate thorn bug is not deterred by these substances. Whether the bugs can use for chemical defense against predators, these substances itself, is not yet clear.

Bidentate thorn bugs eat two to five prey per day and are therefore used for biological pest control. Since the bugs and their nymphs are resistant to some pesticides such as spinosad or methoxyfenozide, they can play a role in integrated pest management.

Bidentate thorn bugs can be a regulatory factor in the population dynamics of many species of butterflies. Both the nymphs and the adult animals feed on, among other caterpillars. It does not matter if the caterpillars move freely or are protected by a cocoon. With the help of her proboscis, in which the mandibles bear stinging appendages, they penetrate the tissue and skin of the caterpillars. The bugs make then a few steps back so that the suction pipe anchored in the skin of the caterpillar and large prey can not wrest. It can also be attacked adult butterflies when they have caught as in a spider's web or are prevented by other circumstances on the fly.