18 THE CANADIAN ENTOMOLOGIST. 



Both species pass through five immature stages, and attain wings at 

 the fifth moult. Under natural conditions the time required for the nymphs 

 to reach maturity varies considerably with the weather. In the Cornell 

 Insectary, which is heated by steam, H. malinus required about 35 days, 

 and Z. viendax about 37 days. Under these conditions each stage lasted 

 about one week. A longer time is required in the orchard. 



The young nymphs of the two species are quite similar. Those of Z. 

 7nendax may be distinguished by their brighter red colour, the absence of 

 dusky markings on the thorax, and by having the body clothed with fine 

 short black hairs. The nymphs of this species retain their bright colour 

 until fullgrown, while those of H. jnalinus become nearly black on the 

 thorax after the third moult. In the nymphs of Z^ vialinus the beak is 

 dusky, while in the other species it is nearly colouiless, with a black tip. 



Description of the Nymph al Stages. 

 H. malinus. 

 Stage I. — Length, 1.2 mm. General colour a light tomato red. 

 Each segment of the thorax has a large, transverse, medially interrupted 

 dusky area, the one on the metathorax being smaller than the others and 

 obliquely truncate laterally. Head dusky, with two oblique light lines, 

 which on the vertex meet the median line of the thorax. Legs, antennae 

 and beak slightly dusky, the antennae yellowish-red at the joints. As 

 growth takes place the first and second abdominal segments shorten and 

 the constrictions become deeper. 



Stage II. — Length, 1.7 mm. Head dusky reddish. Thorax with the 

 median line and the posterior margin of the pro- and mesothorax red, the 

 rest dubky over a red ground colour. Abdomen tomato-red, with irregular 

 lighter markings towards the sides ; first segment with a broad transverse 

 dusky spot, the second with a smaller one, the next six segments each 

 with a very small spot, and the ninth with a large dusky area. Legs and 

 antennae dusky over a red ground colour. Beak dusky. Under parts 

 tomato-red, except a small dark area just above the base of each leg. 



Stage III. — Length, 2.2 mm. Head and thorax dull reddish. A 

 small white area below and behind the eye. The wing-pads begin to show 

 on the mesothorax. Abdomen with a median row of dull reddish spots, 

 those on the first, second and ninth segments the largest. General colour 

 of abdomen bright red, variegated with white laterally, the white markings 

 more pronounced anteriorly. Narrow posterior margin of first and second 



