THE CANADIAN ENTOMOLOGIST 347 



attached to their victims, finally killing them. There are many 

 kinds of parasitic insects, some, the Tachina Flies, resembling- 

 very closely house-flies; others, the Ichneumon-flies, Chalcis-flies, 

 etc., resembling wasps. Some of the Ichneumon-flies are quite 

 large and sometimes haveavery long ovipositor or egg-laying appara- 

 tus, while the Chalcis-flies and Proctotrupids may be extremely 

 small, so small in fact, that one can scarcely see them with the 

 naked eye. Some of these very small parasites attack insect eggs, 

 laying their own eggs in these. A single tiny egg is large enough 

 to supply all the nourishment necessary to carry one of these 

 little creatures through all its stages to maturity. Some parasites 

 lay their eggs on the back of their hosts, but many lay them inside 

 the body. A few species deposit not eggs, but living maggots 

 upon or near the victims. The larvae of a parasite does not, as a 

 rule, kill the thing it feeds upon until it is itself full grown and 

 ready to transform into an adult. 



How useful parasites are can be seen when we remember the 

 severe outbreak of the Army Worm last summer. Towards the 

 end of this outbreak examination in the field showed that there 

 was scarcely one of these caterpillars that was not parasitized. 

 This year I have seen only one Army Worm. Now, the parasites 

 may not be the only cause of the disappearance of this pest, but 

 they are certainly one of the great causes and probably the chief 

 one. 



There are many useful predaceous insects, but I shall mention 

 only two: namely, Ladybird beetles and Syrphus-fly larvae. Every- 

 one knows the pretty little Ladybird beetles with their hemi- 

 spherical shape and often brilliant colours. The larvae of these 

 look like little alligators and are just as fond of destroying other 

 insects as are the adults. Syrphus-fly adults usually resemble 

 small bees or wasps, but they have only two wings. They may 

 often be seen feeding upon flowers or hovering above them. Their 

 larvae are legless, taper towards one end and are stout and usually 

 grayish or brown in colour. The Ladybird beetles and the 

 Syrphus-fly larvae are the two most helpful insects we have in the 

 control of aphids or plant lice. Without their aid it would often 

 be almost impossible to save our crops from these prolific and 

 very destructive little pests. This is, however, only a single il- 



