August, ’24] 
HAMLIN: PRICKLY-PEAR CONTROL 
455 
danger of introducing to Australia many detrimental soil organisms. 
Sterilized sphagnutn moss was found to fill all needs most excellently. 
Figure 2, Plate 7 shows sphagnum being prepared for moistening before 
packing. 
By packing as outlined the cases weighed when full about 200 
pounds, of which about 140 pounds was cactus. 
The consignments of the first eighteen months were sent as excess 
baggage, and shipments were accompanied to San Francisco and seen 
properly placed aboard. This procedure, while essential at first, was 
very expensive. Subsequently the shipments were sent by express, un¬ 
escorted. 
Permission was kindly granted for the shipping cases to be placed on 
the forward end of the bridge deck of the steamer. Here they were 
sheltered behind an equipment house which protected them against 
spray and high waters. They were roped securely in place, and a canopy 
of canvas protected them from excessive sunlight. The removal of this 
covering for two hours during the morning and afternoon permitted the 
entry of sufficient sunlight. 
Success in establishing North American insects in Australia was 
found to depend to a marked extent upon the time of year when 
the shipment was forwarded. Consignments sent in summer or 
winter are immediately subjected to reversed seasons upon arrival in the 
southern hemisphere, and this change renders establishment more 
difficult. It would appear, then, that shipment during the change of 
seasons would be most satisfactory since these changes are simultaneous 
in the northern and southern hemispheres. In other words, a given 
generation having passed through an American summer would, by 
shipment in the fall, continue through the summer conditions in the 
tropics and reach Australia at the beginning of the Australian summer, 
thus experiencing a continuance of unchanging seasons. This expedient 
of prolonging the American season does not hold for consignments dis¬ 
patched in the spring because the winter conditions cannot be prolonged 
by virtue of the necessity of passing through the tropics. That this line 
of reasoning is correct is evidenced by the greater success attendant 
upon fall shipments than spring shipments. The most favorable period 
of shipment from the southern United States to lands across the equator 
extends from September to December. Shipment before September 
allows a touch of winter upon arrival in Australia, while shipment after 
December usually allows the same at this end. 
