485 



were prevented from hatching at a cost of about I65. per milUon. 

 This figure is double the amount estimated by Lunardoni in 1911, a 

 difference that is accounted for by the higher costs at the present time. 

 As the eggs destroyed only represented a portion of those laid in 1917, 

 work against the hoppers was also necessary. Hatching began on 

 17th April and continued until 4th May, owing to the alternating sunny 

 and dull weather. The hoppers were sprayed with sodium arsenite, 

 the strength of which was at first just under 1 per cent, and was then 

 gradually increased to 2 per cent. , as they grew older. The best result 

 was obtained by spraying the insects themselves instead of the grass, 

 Spraying is not a suitable method where the work is on a small scale, 

 owing to the expense of moving the plant, and in such circumstances 

 a poison-bait was used. It was made either of damaged grain, maize 

 cobs (after the maize had been removed) or bran. FuU details are 

 given of the quantities and costs. Against the full-grown locusts a 

 poison-bait was the means used, and it was found to possess a great 

 advantage in that the mortality among the females was much greater 

 than among the males. Whereas the females only numbered from 

 15 to 30 per cent, of the total in a swarm, some 50 per cent, of the in- 

 dividuals kiUed by poisoning were females, which are constantly 

 feeding in order to mature the eggs. It is estimated that the cost of 

 dealing with the adults was sufficiently low to be economically prac- 

 ticable. Two parasites, Tephromyia lineata, Fall., and T. grisea, 

 Meig., attacked many females and rendered them incapable of deposi- 

 ting eggs. The egg-masses were attacked by a Coleopteron, Mylabris 

 variabilis, PaU., and by two Diptera, Cytherea (Mulio) obscura, ¥., and 

 Sysfoechus ctenopterus, Mikn., which were jointly responsible for the 

 destruction of 15-20 per cent, of the eggs. Another fly, Anastoechus 

 nitidnlus, F., was also found, but was very rare and therefore of little 

 importance. This was the first time it has been noticed in Italy, the 

 previous records being from Astrakan [R.A.E., A, ii, 718 ; iii, 636]. 



Details are given regarding the various baits. It was found that 

 crushed grain absorbs 30 per cent, of its weight of hquid, bran 70-90, 

 ground maize cobs 125, slices of dried beet up to 300, white sawdust 

 nearly 100, brown sawdust 70, crushed olive stones 35. To ensure 

 that the bait contained 4 per cent, of its dry weight of sodium arsenite, 

 the solutions had to contain varying strengths of the poison, approxi- 

 mately 13 pe» cent, for grain, 5 for bran, 3"2 for cobs, 1'3 for beet, 4 for 

 white sawdust, 5 for brown sawdust, and 11 '4 for crushed olive stones. 

 It was found that neither grain nor maize cobs alone were suitable for 

 strewing, and therefore use was made of a mixture of grain 7 parts by 

 weight, bran 1|, and maize cobs 1 ; the sodium arsenite solution was 

 diluted accordingly. Bran requires the hquid to be added and stirred 

 in with great uniformity, otherwise lumps are formed, and waste 

 occurs in spreading it. Of the other baits employed, maize cobs, 

 slices of dried beet, and sawdust proved satisfactory. As regards 

 cost, white sawdust was the cheapest ; next came brown sawdust, 

 followed by cobs, beet, bran, crushed olive stones, and crushed grain, 

 There are however other important factors — the capacity for absorp- 

 tion, and the capacity for sweUing, the latter determining the quan- 

 tity of dry substance needed for a wet bait to cover a given area. An 

 equation is given to assist in comparing various baits with due regard 

 to the different factors involved. The addition of molasses, oranges. 



