418 



Heikertinger (F.). Bestimmungstabelle der Halticinengattung- 

 Psvlliodcs aus dem palaarktischen Gebiete mit Ausschluss Japans 

 und der Kanarischen Inseln. [A Key to the Halticine Genus 

 Psvlliodcs from the Palaearctic Region, excluding Japan and the 

 Canary Islands.] — Kolcopt. Rundschau, Vienna, ix, no. 1-3,. 

 30th March 1921, pp. 39-48. 



The title of this systematic paper indicates the nature of its contents. 



Paoli (G.). Considerazioni sui Rapporti biologic! fra le Cavalette ei 

 loi'O Parassiti oofagi. [Considerations on the biological Relations 

 between Locusts and their oophagous Parasites.] — Riv. Biologia,, 

 Rome, ii, no. 4, July- August 1920, pp. 387-397. [Received 

 1st July 1921.] 



The work here described was carried on for three years at Foggia 

 to ascertain why the oophagous enemies of Dociostaurus viaroccantis, 

 Thunb., are not so efficient as their numbers would warrant. 



In Italy the locust eggs are destroyed by a Mylabrid beetle, 

 Mylahris [Zonabris) variabilis, and by two Bombyliid flies, Systoechus 

 ctenopterus and Mitlio obscurus. These parasites do not interfere 

 with each other, and their biology is similar in manj^ ways. In the 

 summer each newly hatched larva enters a recently deposited egg- 

 case and begins feeding on the eggs. At the end of the season or early 

 in autumn it emerges from the egg-case and burrows into the ground. 

 (In the case of Mylabris the larva hibernates as a pseudo-pupa,, 

 becoming mobile again in the spring.) It rises to the surface in the 

 spring, pupates and transforms into the adult. 



The adiilts appear in the areas in which the locust eggs were laid 

 in the preceding year shortly after dispersal of the locusts of 

 the current year. They obtain their food from flowers, in search 

 of which they gradually scatter. The locusts remain in dense swarms, 

 and though they always meet with some enemies, the latter are much 

 more widely distributed. 



Locust outbreaks are the outcome of a progressive increase during 

 a series of years, and their termination is due to a considerable extent 

 to these oophagous enemies and others. 



M. variabilis can parasitise other locusts, such as Calliptamus 

 italicus, besides D. maroccanus, and this seems to appl}' to the two 

 Bombyliid flies also. Moreover, some of the individuals of the three 

 parasites remain in the larval stage for longer than a year. Owing to 

 these circumstances the preservation of their species is assured. 



The percentage of parasitised egg-cases may vary considerably 

 within a distance of a few score yards, but the author's estimate is 

 25-30 per cent, for 1917, while of 5,659 egg-cases examined in 1919, 

 27-9 per cent, were parasitised. 



Other estimates show wide variations, such as from 5-6 to 

 73-3 per cent, in one and the same zone. In a given area the high 

 percentages occur where the egg-cases are few. The general 

 parasitism diminishes as the distance from the original centre of the 

 parasites increases. 



As these observations refer to indigenous insects, the service they 

 render cannot be increased artificially. The only possible way of 

 decreasing the number of locusts by means of oophagous enemies 

 would be by the introduction of such enemies from other countries. 

 The following are some of the species : in Algeria, a Bomb\liid fly^ 



