Genesis of the Lower Hymenoptera (Phytophaga)
It is important to discuss to what extent the conclusions drawn in the previous chapter are in agreement with the facts observed in the life and behaviour of the present-day Hymenoptera. Inevitably, however, it is the difference and not the similarity which first strikes the eye. Whereas, on the one hand, the hypothetical mecopteroid ancestors of the Hymenoptera laid their eggs in cracks and crevices in the soil, that is in a substrate devoid of food, and their larvae were compelled because of this to lead a wandering life and to seek food by their own efforts, on the other hand, no such ‘geobiont’ terrestrial and wandering larvae of this type are known among the Hymenoptera. The Hymenoptera themselves (the most primitive members of the order are, of course, the only ones which can be compared here) are, however, ‘phytobionts’, always laying their eggs on a food-containing substrate, mainly on seed-bearing plants and only occasionally on ferns or horsetails, on which the emerging larvae feed. Correspondingly, as mentioned earlier, the first of these groups are saprophagous in their food habits, while the second group are phytophagous, feeding entirely on living plants. Despite this vast difference between the two, however, remarkable features of similarity are also found, and we shall discuss these presently.
KeywordsPermian Foam Gall Jurassic Bark
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