Description of the insect

• The eggs of Eupoecilia ambiguella are slightly larger in diameter than the eggs of eudemis (0.6-0.9 mm). The distinction between the 2 species is however only reliable after a few days of incubation. The cochylis eggs then take on an orange color (figure 1). The patterns of the chorion (outer wall of the egg) resemble a kind of much looser net in cochylis.
• The caterpillars  of cochylis have a dark brown head, almost black (Figure 2). Their body is orange in color with setae set in rows of dark brown verrucosities. Its behavior is characterized by the almost absence of reaction of the caterpillar to contact. It is much less agile and faster than that of eudemis.
• Five larval stages occur before pupation. For the same stage, the size of the caterpillar can vary depending on the quantity and quality of food available. The head capsule, however, is the most constant part of the body. The widest part is measured in order to characterize the larval stages (figure 3). For this, it is necessary to have a micrometric measurement system associated with a binocular magnifying glass for example.

Measurements of the cephalic capsules of the different larval stages of Cochylis.

These measurements are average measurements commonly used as a reference.

• The pupae measure between 5 and 8 mm and are of a uniform light reddish brown color, a little dark towards the head. They have a collected appearance with an obtuse, truncated end. The rings of the abdomen are furnished with a double row of very fine thorns.
• The adults  of the cochylis are easily distinguished because a black-brown chevron (the broadest base of which is located on the upper costal edge) is present on its forewings which are of a predominantly ocher-yellow hue (Figure 5). The butterfly measures 12 to 15 mm in wingspan. The wings folded over the abdomen at rest show a rather characteristic abrupt projection, a sort of "rooster tail".

Some identification criteria for the 3 main grape budworms are presented in the table in figure 7.