S. myopaeformis is a medium sized species (14–26 mm). The fully black wings and the red band on the abdomen –which is very narrow in the males– are typical of this species. The base of the wings is not diffusely covered with orange-red scales as in S. culiciformis which is often confused with this species. The female is similar to the male but lacks the slender abdomen. The palps are ventrally pure white in the males and brown to black in the females which is another very useful characteristic distinguishing it from S. culiciformis. In the latter, the palps are ventrally bright orange. The proboscis is well developed and functional.
The males are freely attracted to the pheromone developed for this species and are best lured in early afternoon, although the optimal time span is very weather dependent.

The egg is elliptically shaped and light orange-brown.

The caterpillar is off-white but is often found almost 'swimming' in sap of the tree. In these cases, the colour of the caterpillar can be more or less pink. The prothoracic shield is light brown and the head is darker brown. As in all Sesiidae, the prolegs have a double wreath of crochets.

The larva makes irregular galleries and is often found in a flat mine containing a lot of sap from the hostplant.

The caterpillar pupates in a cocoon made of spun small gnawed plant particles and a silken lining on the inside. The pupa is yellow-brown with a somewhat darker head.

The eggs are deposited in crevices in the bark near cankerous swellings, grafts or wound edges. The larva lives between the wood and bark often at the transition zone between dead and living tissue, often in a flat mine that is very moist because of the abundant plant juice. This sap frequently colours the larva with pink and brown stains. In Belgium, the larva of S. myopaeformis usually hibernates once but in unfavourable conditions a second wintering is possible. After wintering, a cocoon is constructed from gnawed plant particles spun together and with a silken lining. It is not uncommon for the cocoon is be located under semi-erect bark pieces.

The larva lives under the bark of old fruit trees of the Rosaceae family, especially Apple, Malus domestica, but also other Malus species, Prunus spp., Crataegus spp., Sorbus spp. and Pyrus spp.

S. myopaeformis finds its optimal living conditions in old apple orchards, but is found also in orchards with low-stem trees, and sometimes in isolated fruit trees in gardens or along roads.