ENTOMOLOGICAL SOCIETY OF ONTARIO. 



31 



pairs of wings ; respiration by means of tube-like structures (tracheal), simple and 

 compound eyes and jointed limbs. Most insects undergo metamorphosis^-that is, pass 

 through a series of well marked changes in their development from the egg to the adult 

 condition. 



Among insects we find two typical mouths : the masticatory or biting, characteristic 

 of beetles and the larvae of many insects ; and the suctorial or sucking, represented 

 in butterflies and plant-lice. A knowledge of these facts becomes of importance in the 

 application of insecticides. Insects with masticatory mouths . can be readily poisoned by 

 applying some poison, such as Paris green, to their food ; but those possessing a suctorial 

 mouth must be treated with a substance that kills by contact and not by being introduced 

 into the digestive system. Such insecticides as Kerosene Emulsion and Pyrethrum powder 

 are suitable for this mode of treatment. Thus, by knowing the nature of mouths, we are 

 •able to suggest what substance is likely to be effective in destroying insects. 



Fig. 21. 



.Fig. 22. 



The development of an insect is represented by four stages — egg, larva, pupa, imago 

 The following figures illustrate the different stages of the Archippus butterfly, a red 

 ;and black species which is familiar to every one. Fig. 22, a represents an egg, highly 



magnified, and c the egg of the nat- 

 ural size on the underside of a milk- 

 weed leaf; b shews the head and 

 anterior segments of the caterpillar 

 before its last moult, at d are the 

 long fleshy horns, which at this stage 

 are tucked under the skin ; e and / 

 shew the arrangement of the bristles 

 on the segments. 



Fig. 23 represents the caterpillar 

 which is handsomely marked with black, yellow and white transverse stripes. 



Fig. 



Fig. 24. 



Fig. 25. 



Fig. 24, shews the caterpillar at a suspended from a little button of silk preparatory 

 to changing into a chrysalis ; at b and c it is making further developments, till it 

 ibecomes a lovely green pupa decorated with a band of golden spots, Fig. 25. 



