1917] Pacific Coast Species of Xylococcus 151 



developed free legs and antennas (PI. XIII, Fig. 7), and the 

 adult male (PI. XIII, Fig. 8) issues from the anterior end, 

 escaping from the cocoon through a small circular aperture. 

 The male is a beautiful insect with two abdominal brushes 

 composed of brittle wax rods produced from groups of pores on 

 the dorsal surface of the sixth and seventh abdominal segments. 

 These brushes are longer than the insect. 



The observations on the life history have been made from the 

 trees where the material was collected and from branches 

 brought into the laboratory and kept alive in water. The 

 different stages were collected throughout the year. The males 

 appear to issue during autumn and early winter and females 

 with eggs are found during winter and spring. The larvae 

 from the eggs of one adult hatch over a considerable period of 

 time. In the laboratory I have had them hatching successively 

 from the same mass of eggs for over six weeks and in the field I 

 found similar conditions. 



The biology of these insects was admirably written up by 

 Mr. H. G. Hubbard (6) in 1898, but a few more facts can now 

 be added. In the adopous stages no external traces of the 

 legs remain, but the antennae are represented by microscopic 

 chitinous discs bearing a few long and a few short hairs. The 

 pigmented eye spots that disappear on boiling the specimens 

 in KOH, are situated near, but not contiguous to these antennal 

 discs. The insects have ten pairs of spiracles, two pairs on the 

 thorax and eight pairs on the abdomen. Those on the abdomen 

 have large simple openings, and within the body form stigmatal 

 tubes with an anterior constriction in which there are one or 

 two rings of pores according to the instar. The thoracic 

 spiracles have no stigmatal tubes. In the active stages their 

 openings are marked by a small group of pores, and in the 

 apodous stages these pores are wanting. In the successive 

 apodous instars an increasing development of the anal tube is 

 visible and this is one of the means of' distinguishing them. 

 Mr. Hubbard laid stress on the unusual life history of Xylococcus 

 betulce Perg. and pointed out many peculiarities of structure, 

 showing parallels to them in several species of Coelostoma Mask. 

 {Coelostomidia Ckll.) and of Mar gar odes Guilding. He sug- 

 gested that these belonged to a hitherto unrecognized sub- 

 family of the Coccidce. Since that time Xylococcus and five 

 other genera. Mar gar odes, Coelostoma, Callipappus, Kuwania 



