THE CANADIAN ENTOMOLOGIST. 



57 



AN IMPORTED RED SPIDER ATTACKING FRUIT 



TREES. 



BY L. CAESAR, PROVINCIAL ENTOMOLOGIST, GUELPH, ONT. 



For some time the writer had suspected that the Red Spider 

 so common on fruit trees in Ontario was not our common species, 

 Tetranychus himacidatus. Accordingly specimens were , sent in 

 September, 1912, to Mr. Nathan Banks of the Bureau of Ento- 

 mology, Washington, D. C, with some details as to the extent of 

 its distribution and the food plants attacked. In reply Mr. Banks 

 stated that the species was Tetranychus pilosus, an European 

 species that attacks fruit trees, and that its relationship to Tetrany- 

 chus mytilaspidis, which feeds chiefly on oranges, was very close 

 and, perhaps, identical. 



Tetranychus pilosus is about the same size as himacidatus, but 

 dififers from it in several respects: — It is more nearly circular in 



outline, somew^hat stouter and has 

 a number .of distinct white tuber- 

 cles on the dorsal surface, with a 

 fine hair arising from each. It is 

 dark red in colour, many specimens 

 being blackish, with the mouth 

 parts and usually a dorsal longi- 

 tudinal area much paler than the 

 rest of the upper surface, whereas 

 the colour of T. himacidatus varies 

 from greenish yellow to red. The 

 latter species feeds largely on the 

 lower surface beneath a fine silken 

 web, in or under the protection of 

 which it lays its eggs; the former 

 feeds and lays its eggs on both 

 surfaces, and makes no web, but fastens its eggs by a few fine 

 silken threads to the leaf or twig on which they are laid. The 

 eggs are uniformly blood red, while those of himaculatus are pearly 

 white. T. pilosus passes the winter in the egg stage, these being 

 deposited in the axils of the twigs and branches. T. himaculatus 

 passes the winter as adults in the ground or in sheltered hiding 

 places. 



February, 1915 



Fig. 5. — Tetranychus Irtitosus. adult female, 



greatly enlarged. 



(Drawn by Miss M. Hearle.) 



