Description of pupal instars of Kermes quercus (Linnaeus, 1758) (Hemiptera: Kermesidae)

The third instar male (prepupa) and fourth instar male (pupa) of Kermes quercus are described and illustrated, with the differences between them being indicated. The prepupa has a broadly oval, membranous body, with indistinct segmentation, 9-segmented antennae, 3-segmented legs, anterior wing-buds extending to about the base of the metathoracic legs, and a broadly rounded medial penial lobe. The pupa has an elongate oval body, with more distinct segmentation and more strongly developed appendages: 10-segmented antennae, 5-segmented legs, wing-buds extending laterally past the coxa of the metathoracic legs, and a long, triangular penial lobe.

Developmental stages in the Digenea

The naturally oviposited egg of Dasymetra conferta is fully embryonated and it hatches only after it is ingested by the snail host, Physa spp.Hatching appears to be in response to some stimulus supplied by the living snail. The stimulus causes the larva to exercise a characteristic series of body movements and to liberate a granular sustance (hatching enzyme) from the larger pair of its cephalic glands. This enzyme reacts with the vitelline fluid to create pressure within the egg capsule, and with the cementum of the operculum, so that it may be lifted away. The larva's escape from the shell, therefore, is due to a combination of pressure and body movements.The hatched larva has a membranous body wall, supporting six epidermal plates, an apical papilla, two penetration glands and a central matrix (the presumptive brood mass).It lives for about an hour within the snail and during this time there is a reorganization of the central matrix which terminates in the formation of an 8-nucleated syncytial brood mass.The miracidial ‘case’, consisting of the body wall and the epidermal plates, ultimately ruptures to liberate the brood mass. Once the brood mass is free it penetrates through the gut wall in an incredibly short time.

Corrosion Inhibitors for Steel★

Many inhibitors, added to water or chloride solution in amounts insufficient to stop attack altogether, produce localized attack, which is more intense than the general corrosion met with in the absence of an inhibitor. Inhibitors which are free from this danger are, in most cases, inefficient. It is believed that the danger is connected with the formation of blister-like membranes over the sensitive points, which prevent the access of the inhibitor to those very points where it is required. By using, suitable mixtures of phosphate and chromate (or phosphate and persulphate), so that any substance precipitated will not be ferrous phosphate but ferric phosphate a crystalline non-membranous body), the danger can be avoided. Even if the mixture is added to an amount too small to stop corrosion altogether, no intensified corrosion or pitting is observed.