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A NEW SPECIES OF PARAPHELINUS, PERK., FROM BRITISH GUIANA, 

 WITH A DISCUSSION OF THE GENUS AND THE ALLIED 



APHELINUS, DALM. 



By James Waterston, B.D., B.Sc, 

 Imperial Bureau of Entomology, London. 



During the past summer (1916) Mr. C. B. Williams has, on behalf of the Depart- 

 ment of Agriculture, Trinidad, been engaged in investigating the natural enemies 

 of Tomaspis and its allies, in the hopes of finding some effective means of controlling 

 the froghopper, Tomaspis saccharina, Dist. , which in recent years has caused consider- 

 able damage to the sugar plantations of Trinidad. With this object Mr. Williams 

 has made collections of minute parasitic Hymenoptera in the Island and the adjacent 

 mainland of British Guiana, and this material has from time to time been forwarded 

 to me for study. Mr. Williams has from the first been fully alive to the importance 

 of securing any specimens of the egg-destroying Paraphelinus, Perk. , and I am glad 

 to find species of this interesting genus in the gatherings from both Trinidad and 

 British Guiana. The literature dealing with Paraphelinus is scattered and perhaps 

 inaccessible to those to whom it is most likely to prove serviceable. I have therefore, 

 in some introductory notes, recapitulated the main facts in the life- history and host 

 attachment and added a bibliography to the present paper. 



As an economic insect Paraphelinus owes its importance to the fact that while 

 most Aphelininae attack Aphids, Coccids, and Aleurodids, this genus destroys the 

 eggs of Xiphidium and Tomaspis. Although the genus is of comparatively recent 

 erection, it is likely, as Dr. Perkins pointed out in his original description, that 

 Agonioneurus locustarum, Giraud, bred from the eggs of a grasshopper, Xiphidium 

 fuscum, is really a Paraphelinus. P. xiphidii, Perkins, is an efficient controller 

 (Swezey, 2, 4) of Xiphidium varipenne, Swez. The parasite was first observed in 

 March, 1905, in the grounds of the Hawaiian Sugar Planters Association's Experi- 

 ment Station, Honolulu, where it had almost certainly been introduced. 



The eggs of the Xiphidium are laid in clusters just beneath the leaf -sheath of the 

 sugar-cane, where they are attacked by the parasite ; 7-14 examples of Paraphelinus 

 may emerge from a single egg and occasionally the whole cluster of eggs (2-15) is 

 affected. Like many species of which several imagines emerge from a single host, 

 all the individuals in a brood of P. xiphidii use the same hole of emergence, which is 

 gnawed by the first to hatch out. The aperture is circular, and when the host egg is 

 closely pressed against the leaf- sheath, the latter as well as the egg-shell may be 

 gnawed through. If the Xiphidium egg is examined in balsam after the parasites 

 have emerged, the empty pupal envelopes of the Paraphelinus may be seen, together 

 with numerous darker granules within the shell. These granules are the accumulated 

 foecal matter which is discharged by the insect shortly after emergence. Para- 

 sitised eggs are bluish-black in colour. The life-cycle of Paraphelinus varies from 

 20-31 days, that of the host being three months ; the parasite is thus placed at a 

 distinct advantage, and shortly after it was first noted, proof of its beneficial work 

 was given by the rapid disappearance of Xiphidium in some districts. 



