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The External Morphology and Life-history of the Coccid Bug, Orthezia urticœ Linn.



All stages of the Coccid Bug, O. urticœ, were collected and bred in the laboratory to investigate the number of instars and the morphology.

The first and second instar larvæ are sexually indistinguishable. The male has two larval, two nymphal, and a winged adult stage. The female has three larval and a wingless adult stage.

Breeding and growth take place rapidly between May and the end of August. The males attain the adult stage in March, and are found in very small numbers until the middle of June. The females begin to form their brood-sacs in May or June, and reproduce throughout the summer months. From the beginning of September to the end of January the insects hibernate.

The occurrence of O. urticøE in its different instars is summed up in the table see (p. 303), from the events noted during the time I have had the Coccids under observation.

In the external morphology it is noticeable that there is a breaking-up in the wax plates to coincide with the segmentation of the insect, and extra intermediate blocks are cut off from the originally-placed main blocks. The glandular setæ become more numerous from the first to fourth instar of the female, and the outline of the insect becomes almost circular, the abdomen shortening considerably in the adult stage. The male nymph of the third and fourth instars possesses external wing-stumps on the mesothorax, and an indication of metathoracic halteres is seen on the fourth instar nymph. The adult male has a pair of mesothoracic wings, but flies very little and only lives for a few days.

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