The locust plague and its suppression / by Æneas Munro.

  • Munro, Aeneas.
Date:
[1899]
Catalogue details

Licence: Public Domain Mark

Credit: The locust plague and its suppression / by Æneas Munro. Source: Wellcome Collection.

    62/388 page 38
    to a short strong square trunk or thorax; four wings, two antennae, six legs, and a long segmentary abdomen (Fig. 4). 86. The ground colour of the locust is generally brownish—straw - or red—but the colour varies somewhat, according to the particular company or season of the year, or some other unknown circumstance, such as that connected with the hatching, or age or food, or some pro- vision of nature by which they are made to resemble the leaves, grasses, or pastures in which they exist for the time being, for purposes of protection or warning—probably the former, but which variation does not probably signify any great change in the species.1 That is to say, that locusts of one particular colour, as observed by us at any one time, may become themselves changed in colour, or give birth to a generation which presents to us a somewhat different shade of colour when seen by us at another time. Therefore in one year you may see a flight of locusts of a more marked red colour than the brown or pale- straw of the previous year, and vice versa. Mere ground colour is immaterial, and does not signify another species. Three distinct ground colours have been observed—namely, yellow, red, and grey. Upon these ground colours may be found markings of a black, white, or coffee colour, which conveys to the eye the general impression which characterises the particular company in question. It may be that the nature of the food, or the age and condition of the insect, or the influ- ence of the sun, in some occult way may make or account for the difference in colour; but at anyrate, so far as can be detected from the habits of the species so far as the different varieties of colour are con- cerned, in other respects they are precisely the same. It is probable 1 Mr. Bruner (p. 9 of Report) says : “Thus we find that the same insect exhibits three distinct colour-variations during its life as a Voladora. Similar colour-variations have been reported in the Old World Peregrina, as seen in different regions, at times visited by it. But we do not recall any record of an attempt at an explanation for these variations in the insect. Similar but less decided variations in colour have been observecf-by us in wintering locusts in North America. In fact, most of the brown or yellowish-brown locusts become more or less tinged with red late in fall, after they have been several times exposed to frosts.” On page 18 he says : “ These invading swarms are usually composed of insects that have wintered as Voladoras in the ‘ Chaco,’ as is the almost general feeling here in Argentina. They are, as a rule, of the dark or reddish form. This, as shown in a preceding page, indicates that they are old locusts, which have wintered over.” On pa|je 85, at the close or sum- mary, he says: “That it winters as a Voladora in the vicinity of the 30th degree of south latitude ; and also that the freshly-winged, the wintering, and the egg-laying insects can each be recognised by their prevailing colours. In other words, these three stages in the insect’s career are to be known by special colour-characteristics we have ascertained, or believe we have,” etc. The late Professor Drummond, in that interesting chapter on Mimicry in his Tropical Africa, says: “A still more elaborate set of forms are those which represent leaves. These belong mostly to the mantis and locust tribes, and they are found in all forms, sizes, and colours, mimicking foliage at every stage of growth, maturity, and decay.”
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