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Abstract. Monogeny, the production of unisexual broods by individual females, is widely recorded in gall midges (Diptera: Cecidomyiidae). Theoretical models propose that the adjustment of offspring sex ratio by females may pre-dispose the evolution of monogeny in gall midges however empirical studies in this field are superficial. Expressed more simply, monogeny may enable individual female gall midges to decrease or increase the number of male and female progeny they produce in response to changes in environmental conditions. Host quality/size is repeatedly reported to influence sexual investment in insects in terms of sex ratio adjustment. In this paper, we examined the sex ratio of the offspring of the monogenous predatory gall midge Aphidoletes aphidimyza attacking low and high abundances of the cotton aphid, Aphis gossypii. Two consecutive generations of female gall midges were presented with either a low or high abundance of aphids in each generation and the sex ratio of their progenies determined. There was no difference between the sex ratio of the progenies that developed on the high or low abundance of A. gossypii in the two generations. Apparently, the females did not regulate the number of female and male progenies, or adjust the numbers of male or female's eggs they produced in response to the changes in the abundance of prey. Results of this study do not support the theory of sex ratio regulation proposed for monogenous gall midges. It is likely that the skewed sex ratio in most species of monogenous gall midges is a consequence of differential mortality of male and female progenies under harsh conditions. The finding that male and female larvae did not differ in the number of aphids they require to complete their development supports this claim.

Summary. -Cucumber mosaic virus (CmV) is one of the most important legume-infecting viruses, which is transmitted effectively by pea aphid Acyrthosiphon pisum (harris) (hem: Aphididae). Transmission efficiency of two CmV isolates (As and Kh from cowpea and bean hosts, resp.) by red and green color morphs of pea aphid were evaluated on bean plants. Triple-antibody sandwich elisA (TAs-elisA) using CmV-specific monoclonal antibodies revealed that both CmV isolates belonged to the serotype ii. bean plants inoculated by viruliferous aphids were assayed by double-antibody sandwich elisA (DAs-elisA) at 16 days post inoculation (dpi). The results showed that the transmission rate of CmV-As by the red morph was significantly higher than by the green morph, resulting in significantly higher transmission rate of the virus (As + Kh) by the red morph than by the green morph, with p≤ 0.1. similarly, the efficiency of CmV transmission by the red morph of A. pisum was higher than the efficiency of transmission by the green morph. The higher transmission rate and efficiency of CmV by red pea aphid would be important in the epidemiology. based on these results, we hypothesize that the transmission efficiency of CmV is affected more by the difference in transmission determinants of A. pisum color morphs than by the sequence of virus coat protein determinants.Keywords: Aphididae; bromoviridae; color polymorphism; transmission efficiency * Corresponding author. e-mail: adizaji@ut.ac.ir; phone: +98-26-32818705. Abbreviations: CmV = cucumber mosaic virus; CP = coat protein; DAs-elisA = double-antibody sandwich elisA; dpi = days post inoculation; Dsmz = Deutsche sammlung von mikroorganismen und zellkulturen; mAb = monoclonal antibodies; PbsT = phosphate buffer saline-Tween; PmV = pea mosaic virus; PVP = polyvinyl pyrolidone; TAs-elisA = triple-antibody sandwich elisA

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