The macroscopic Differentiation of Anopheline Eggs according to their Pattern on the Surface of Water

Extract

Thus far nine species of Anopheles have been found in Palestine. These, in order of frequency and importance, are : A. elutus, Edw., A. superpictus, Grassi, A. sergenti, Theo., A. multicolor, Camb., A. claviger, Mg. (bifurcatus, auct.), A. algeriensis, Theo., A. hyrcanus, Pall., A. pharoensis, Theo., and A. coustani, Lav. (mauritianus, Grp.).

The morphological characters of the eggs of these species have been described and are well known. Workers have, however, overlooked the fact that their eggs arrange themselves on water in specific patterns, determined apparently by their structure. Observations made during 1939–41 have shown that, if a number of eggs is placed on a drop of water, they assume a pattern characteristic of the species. This pattern arrangement makes possible a macroscopic differentiation of species in the field.

Observations have been made on ovipositions of all the species, but more particularly of A. elutus (188 ovipositions), A. sergenti (365 ovipositions), A. superpictus (149 ovipositions) and A. multicolor (51 ovipositions). These results indicate that these species arrange themselves into two types of patterns :—

i. Eggs arranged in parallel patterns. To this group belong those species that breed in open unshaded water : A. elutus, A. superpictus, A. multicolor.

ii. Eggs arranged in angular patterns, the eggs lying at an angle to one another, in the form of stars, etc. This group comprises the six remaining species, all of which prefer shaded places for their development.