1917] Pacific Coast Species of Xylococcus 149 



former in California and the latter in Japan, Xylococcus macro- 

 carpcB Cole, infesting the Monterey Cypress, and Xylococcus 

 alni n. sp., infesting alder trees. From this list it is seen that 

 not only are those insects widely distributed geographically, 

 but they are found on widely separated species of host plant. 

 Nothing is known as to how the trees have become infested, or 

 how the insects penetrate into the lower layers of the bark, 

 where they are found surrounded by secretions of wax. 



It is of peculiar interest that the Monterey Cypress, the host 

 of Xylococcus macrocarpce Cole. (PI. XII, Fig. 1), is indigenous 

 to a single area in California known as Del Monte Forest and 

 extending for a few miles along the Pacific Coast in Monterey 

 County. While collecting my specimens I found the insects 

 on old and young trees alike. The infestation is not evenly 

 distributed in the forest and the most heavily infested trees are 

 easily distinguishable even at a distance by their black colour, 

 due to the grow^th of a sooty mould fungus in the honey dew 

 exuded by the insects. 



Xylococcus quercus Ehrh. (PI. XII, Fig. 2) I have collected 

 from oak trees (Quercus chrysolepis Liebmann) in Permenente 

 Creek Canyon, Santa Clara County. There is a slight growth 

 of sooty mould fungus on these infested trees also. 



These insects infest the trunk and older branches of the trees, 

 and their presence is indicated by numerous filaments of wax 

 protruding from crevices in the bark and bearing drops of honey 

 dew. There is great variety in the length and appearance of 

 these filaments, some being straight, others wavy and almost 

 spiral. This filament is a capillary tube issuing from the 

 posterior end of the body from a chitinous organ called the anal 

 tube, and formed by an extension of the outer walls of circles 

 of chitinous spinnerets, that open into and surround the posterior 

 end of the alimentary canal. Gross dissection shows the 

 insects imbedded between the layers of the bark with their 

 mouth-parts penetrating more deeply. They are surrounded by 

 a homogeneous layer of wax that is given off from pores scattered 

 over the body (PI. XIII, Fig. 1). The apodous stages of the 

 insect are found in greatest number and in the case of Xylococcus 

 macrocarpce Cole, the characteristic position is in groups varying 

 in number (PL XII, Fig. 3). Xylococcus quercus Ehrh. 

 (PL XIII, Fig. 2) and Xylococcus alni n. sp. (PL XIII, Fig. 3), 

 are seldom found in groups and their pits are more or less 



