1921 ENTOMOLOGICAL SOCIETY. 21 



It is no wonder that these breeding grounds become literally packed with 

 eggs, yet it seems remarkable that the lands so close around should be practically 

 without them. I have observed places where it was impossible to stick the point 

 of a knife into the ground without revealing a sac of eggs. In others I counted 

 fully 3,000 eggs to a square foot of sod. 



As noted above, these breeding places become very much denuded of vegeta- 

 tion, and they are, consequently, easily noted even at a distance. This fact has 

 been of great value to us in scouting for eggs, as it has enabled us to drive quickly 

 over the country and pick out the infested places from a motor car. We have also 

 been able to make practical recommendations to the farmers for dealing with these 

 egg areas. 



Apart from the two main locusts mentioned before, we have had several others 

 of less importance. In some districts the Two-striped locust occurred in large 

 numbers and its egg masses of sixty or more eggs were not uncommon last fall. 

 The Bed-legged locust was also present in all parts and was especially noticeable 

 late in the season due to the fact that it appears later in the spring and is conse- 

 quently later in maturing. This last insect inhabits rather wetter ground than 

 does atlanis. 



The natural control of locusts involves many factors, some at least of which 

 are imperfectly understood. That dryness favours the insects' increase, is generally 

 acknowledged, just as wet seems to produce a contrary effect, but we have 

 yet to learn when these factors come most into play. My own experiments go to 

 show that cold in itself does not affect the eggs but that heat does. Thus eggs 

 exposed to all the vicissitudes of "winter on top of the ground came through 

 without important mishap while similar ones exposed to the sun in April and 

 May were nearly all destroyed. Eggs exposed in September in the same way 

 also lost their vitality. 



The most interesting part of the work, in my estimation, has been that of 

 watching for the causes which must eventually reduce the pest to insignificance. 

 They are undoubtedly at work around us now, but so many circumstances arise 

 in connection with them that it is very difficult even at this time, to accurately 

 forecast what agencies will ultimately bring the insects under control. 



In 1919 we had reason to expect that flesh flies, among which Sarcophaga 

 kellyi was prominent, would prove an important factor in the locusts control, but 

 unfortunately the large increase of the previous year was not maintained in 1920. 



The common fungus disease, Bmpusa grilli, did much in restricted areas, and 

 took locusts sparingly nearly everywhere in both 1919 and 1920. It is one of 

 those diseases that appears with great suddenness over large sections of the country 

 but is checked with equal rapidity. 



Locust mites (Trombidium sp.) have increased enormously and during the 

 present year fully seventy per cent, of the species of Melanoplus were heavily 

 infested. Their presence on the locusts, however, appeared to produce little effect 

 and when they dropped off in the course of a few weeks, the locusts went about 

 their work apparently none the worse for the experience. 



It is interesting to note here, that the Road-side locust escaped these mites 

 almost entirely even when the two genera intermingled. 



While mites appear to play but a minor part in reducing the adult locusts 

 it is possible that they are of more importance as destroyers of locust eggs. I 

 found them not uncommonly in egg sacs of Melanoplus where they appeared to 

 be doing excellent work, but here again Camnula escaped their attack. 



