35 



the penultimate larval stage ends and the final stage begins. Of this, 

 however, we are certain, that there is an inactive period, or at least 

 what we may consider such, although neither larva nor pupa is truly 

 quiescent, of at least two weeks during which the larva remains in its 

 pupal cell. 



The entire cycle from the date of laying of the eggs to the issuance 

 of the first adult was between eight and ten weeks. 



From the above data the approximate life cycle for the first spring- 

 generation may be deduced as follows: 



Days. 



Egg period, from laying to hatching 12-18 



Active, feeding stage of larva 24-31 



Inactive or nonfeeding larval stage 14 



Pupal stage 6-7 



Entire life cycle 56-70 



NATURAL ENEMIES. 



As only a single lot of this species was used in rearing, no parasites 

 were developed. In one instance, however, an adult fly, not yet 

 mature, was found to have succumbed to mites and it has already been 

 stated that eggs were destroyed by red spiders. No larvae died as far 

 as noticed, although the first generation was exposed to a temperature 

 which was below freezing out-of-doors and not much higher in the 

 rearing jar, which stood near an open window in an unheated room. 



REMEDIES. 



The violet sawfly is amenable to the same remedies that have been 

 found most useful against the greenhouse leaf-tyer in greenhouses. 

 Hand-picking of the larvae has been employed with some success by 

 Mr. Dorsett and others, but is too slow to be entirely satisfactory and 

 the larvae are difficult to discover. Extract of tobacco diluted at the 

 rate of 1 part extract to 30 parts of water was also effective when 

 applied as a spray, but florists are opposed to the use of tobacco on 

 violets owing to its tendency to weaken the plants and to bring on 

 the condition known as "spot." The main reliance at present is in the 

 hydroeyanic-acid-gas treatment, as described in the foregoing article 

 on the greenhouse leaf-tyer. 



THE TWO-SPOTTED RED SPIDER. 



(Tetranychus bimaculatus Harvey.) 



Perhaps the most troublesome of greenhouse pests, everything con- 

 sidered, are minute reddish spider-like creatures known popularly as 

 "red spiders." They often do very considerable damage in flower 

 and vegetable gardens, but in greenhouses they attain their greatest 

 destructiveness, and are particularly injurious to violets and roses, as 

 well as to a great variety of other plants. 



