Megaselia scalaris
(Diptera: Phoridae) is regarded as a medically important insect worldwide
because it is the source of different myiasis diseases. Therefore, it should be
controlled for human welfare and for economic reasons. Accordingly, the larvicidal activity of six plant essential oils was
determined against M. scalaris and their impacts on proteins and
isozymes were also estimated in whole body homogenate of the third larval
instars. The tested essential oils were chamomile (Matricaria chamomilla),
clove (Syzygium aromaticum), orange (Citrus sinensis), rosemary (Rosemarinus
officinalis), spearmint (Mentha spicata) and sweet basil (Ocimum
basilicum). Results exhibited that the clove oil had the highest larvicidal
activity, LC50 is 2.38 ml/100g media, whereas, chamomile oil was the
least one, LC50 is 5.37 ml/100g media. Significant
concentration-mortality responses of the treated larvae were observed towards
all tested oils. Concerning protein estimation, the control protein content was
12.80±2.68 mg/g tissue, and the oil application produced an elevation in total
protein contents in treated larvae. This elevation was significant (p<0.05)
with clove, orange and spearmint oils amounted to be 92.19, 70.31 and 57.58%,
respectively, compared to that of the control larvae, but insignificant (p>0.05)
with chamomile, rosemary and sweet basil oils. The electrophoretic study
revealed that the maximum number of native protein bands was seven at
approximately rate of flow ranging between 0.14 to 0.72 in the control and
clove, orange, spearmint and sweet basil treatments. One newly formed protein
band was observed in whole body homogenate of clove, orange, rosemary,
spearmint and sweet basil treatments. The profiles of β-esterase,
alcohol dehydrogenase and aldehyde oxidase showed the same patterns in both
control and treated larvae. On the other hand, there was a reduction in the
isozymes amount percent in the treated larvae as compared with the control
values. The biochemical changes in native proteins and isozymes could be used
as a biochemical indicator of toxic stress.