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Immature Stages of Eurytomidae


Immature stages of Eurytomidae were discussed in detail by Clausen (1940), as follows:


There is a considerable degree of uniformity in the eggs of the known species of the Eurytomidae.  In the majority of cases, the egg is oblong in form with a somewhat col­lapsed stalk at the anterior end and a flagellum of varying length at the opposite end.  The stalk may range in length from half that of the egg body to five or 6X its length, as in Macrorileya oecanthi.  In this species, the stalk is much more slender than usual, being virtually a filament.  In some species, the posterior flagellum is greatly reduced or lacking.  In the externally deposited eggs of Eurytoma, the chorion exhibits a distinct sculpturing which, in E. pissodis Gir., is described as a black pubescence, while in others it is stated to consist of short but strong "spines" (Fig. 89A).  These spines are densely placed and give the egg a color ranging from brownish to black.  The stalk and flagellum lack this sculpturing.  The ovarian egg of E. oophaga Silv. has reticulate markings on the chorion; after deposition, this sculpturing is in the form of fine spines.  The egg of E. curta is cylindrical and mea­sures 0.4 by 0.07 mm.; the stalk is 1.1 mm. in length, and the chorion is unsculptured.  Eggs of Macrorileya and Archirileya likewise lack the surface sculpturing.


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                           Fig. 89


The first‑instar larvae of the family are broadly oval to elongated in form, with 13 distinct body segments and a relatively large, hemispherical or conical head.  The head bears a number of sensory setae which, in E. appendigaster, are very large.  The sensory setae, of which there are four pairs on each thoracic segment and three on the abdomen, may be minute, as in E. curta, or may exceed the length of a segment, as in E. robusta and E. parva.  The integumentary setae are abundant in Eurytoma and may completely clothe the body or occur as a band on each segment.  The larva of A. inopinata is apparently devoid of setae.  In E. rosae Nees (Fig.  89B) and E. parva, a pair of small, sclerotized processes of unknown function is found on the venter near the median line of the first thoracic segment.  The normal equipment of spiracles in the family is four pairs, situated on the mesothorax and the first three abdominal segments.  E. parva has five pairs, the additional one being on the metathorax. E. curta is provided with 10 pairs, on the second and third thoracic and the first eight abdominal segments.  A. inapinata has eight pairs, situated on the mesothorax and the first seven abdominal segments.


The second‑instar larva has been described for only a few species; it differs from the preceding instar mainly in the reduction of the sensory setae.  E. oophaga still has the four pairs of spiracles situated as in the first instar; in E. parva the number is increased from five to nine and in A. inopinata from eight to nine.  They are situated on the last two thoracic and the first seven abdominal segments.  E. dentata Mayr has eight pairs, that on the second thoracic segment being absent.


Five larval instars have been distinguished in a number of species, and this is presumably the normal number for the family, though only four are indicated for E. oophaga.  In this species the full complement of nine pairs of spiracles appears first in the third instar.


The mature larva of Eurytoma is more robust than the preceding instars.  The sensory setae are usually small, though they are relatively long in E. dentata and E. masii Russo (Fig. 89C).  Cuticular spines are minute or lacking.  The larvae of Archirileya (Fig. 89D) and Macrorileya differ markedly from those of Eurytoma, being cylindrical, with the caudal segments broad and the last one broader than those pre­ceding it and forming a disk or sucker.  There are 12 apparent body segments rather than the usual 13, and the anterior ventral region of the abdomen is appreciably distended.  Intersegmental welts occur dorsally from the first thoracic to the sixth abdominal segments.  The larvae of Axima and Conoaxima have large median dorsal welts on the thoracic and the anterior abdominal segments.  The nine pairs of spiracles, on the second and third thoracic and the first seven abdominal segments, occur in all genera, though E. curta is stated to have an additional vestigial pair on the eighth abdominal segment.


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