DESCRIPTION OF THE DEVELOPMENTAL STAGES OF THE MITE PREDATOR , OLIGOTA OYIFORMIS CASEY , WITH NOTES ON THE OSMETERIUM AND ITS GLANDS ( COLEOPTERA : STAPHYLINIDAE ) BY

Oligota ovi[ormis was described by Casey in 1893. Quayle (1912, I913) called attention to the fact that both larvae and adults were predaceous on spider mites and consequently beneficial in orchards where mites were a pest. Quayle partially outlined the life history of O. ovi[ormis but was unable to, induce pupation. Ewing (I914) and Essig (1926) reviewed Quayle’s work. Badgley and Fleschner (I956) were able to induce pupation by providing a floor of sand in which pupation took place. However, little detailed description of the early stages was provided. A brief account of the osmeterium of the larva and its protective opercula was given by Badgley and Fleschner. The osmeterium is o,f particul’ar interest as its occurrence appears to be widespread anaong the Aleocharinae, although it has been misinterpreted (Badgley and Fleschner, I956).

(I956) were able to induce pupation by providing a floor of sand in which pupation took place.However, little detailed description of the early stages was provided.A brief account of the osmeterium of the larva and its protective opercula was given by Badgley and  Fleschner.The osmeterium is o,f particul'ar interest as its occurrence appears to be widespread anaong the Aleocharinae, although it has been misinterpreted (Badgley and Fleschner, I956).

Larva of Oligota oviformis Casey
Length 2.1 mm (mature larva).Body elongate, subcylindrical, tapered at each end; integuments soft, not chitinize.d,without dis- tinct sclerites; pale testaceous with the opercula of the osmeterium piceous, darkest along the posterior margin of eighth tergite, os- meterium bright orange.Head oval, about as wide as long, with a single ocellus on each side behind the antennal tossae.Epicranial suture absent.Antennal fossae located at sides of head outside the bases of the mandibles.Antennae three-segmented; first segment about as long as wide; second segment narrower than first, a little more than twice as long as wide, with two long setae near the middle and a modified "acorn seta" without obvious articulation at base; third segment about half as wide as second and a little more than twice as wide, with two long setae at apical third and a shorter       rowed in apical two-fifths, arcuate externally, pointed at apex.Maxillary palpus three-segmented; first segment somewhat longer than wide, narrowed to apex; second segment a little narrower than apex of first, almost twice as long as wide, nea.rly paraliel sided; third segment narrower at base than apex o.f second, almost four times as long as wide, gently arcuate, gradually pointed to apex.Labial palpus two-segmented; first segment about as long as wide.; second segment narrower than first, a little more than twice as long as wide, slightly arcuate, gradually narrowed and pointed to apex.
Pronotum wider than head, narrowed in front, wider than long, with a row of our setae along front margin, a pair of setae on disc, four setae along lateral margin, two setae in sub-lateral series and six setae along posterior margin.Mesonotum about as long and a little wider than pronotum, with no setae at anterior margin, six transversely arranged on disc, two in the lateral series and six in the basal series.Metanotum about the same size and shape as meso- notum with chaetotaxy the same.Abdomen.First abdominal seg- ment about as wide as metanotum and half as long as metanotum; without setae at anterior margin; with two transverse rows of discal setae, the first of two setae and the second of ten setae, with ten setae along the posterior margin and three or four irregularly placed setae at each side.Second abdominal segment about as wide as first and ahnost as long a.s metanotum; with setae arranged almost as on first segment except the setae are moved forward so that there are two discal series of eight setae each and none along the posterior margin.Third through seventh segments very similar in all respects to s'ecend except the seventh is narrower than the sixth and the two anterior setae are lacking on all but the first two segments.Eighth segment narrower than seventh but about as long; with two dark conjointly oval opercula in the middle near the posterior margin, divided longitudinally so that the anterior operculum is the largest; with chaetotaxy as on seventh segment.Ninth segment narrower than eighth, about as long as wide; with two.discal setae and about eight or ten setae along the posterior margin; the outer apical angle produced on each side in a pointed fleshy urogomphus which ap- parently has no basal articulation and is unsegmented.Pseudopod produced between and beyond urogompi.Spiracles present at the outer margins of the mesothorax and the first seven abdominal seg- ments with much the appearance of empty hair follicles.
The larva of Oligota ovi[ormis is similar to that of O. flavicornis Boisduval and Lacordaire as described and illustrated by Paulian (I94I).The two species differ in that in O. ovi[ormis the "acorn seta" of the second antennomere is almost as long as the third seg- ment and has no distinct articulation at its base whereas Paulian's illustration of O. flavicornis shows two very small "acorn setae" with distinct articulations at the base.In O. ovi[ormis the uro- gomphus is an extension of the .eighthsegment without articulation or segmentation.In O. flavicornis it is distinctly two-segmented.
Pupation takes place in cocoon in which the pupa is quite loose.The cocoon is formed of sheets of silk to which grains of sand adhere.In one instance the cocoon was formed in part of several sheets of silk extending like short walls perpendicular to the axis of the pupa.

Pupa of Oligota oviformis Casey
Pupa exarate, pale yellow, ovid, about one and one-hal times as long as wide, not chitinized in any part, without tubercles.Head ventrally reflexed so that none o it is visible rom above; with a single dark eye spot on each side; with two long setae above each eye spot.Ironotum hemispherical, wider than long; with a row of setae along the anterior margin, the two outer and -he middle setae distinctly longer than the other six.Elytra each about as long as wide, about as long as pronotum, with outer apical angles broadly rounded and inner apical angles narrowly rounded.Wings as seen rom below .almosttwice as long as elytra.Abdomen apparently eight-segmented as viewed along the side margins of the paratergites; segmentation of tergites and sternites indistinct; segments two through seven each with a short seta on each side of side margin; eighth segment with a diaphanous bidentate process at apex each toot'h of which is swollen at tip.Three specimens reared rom larvae collected at Riverside, River- side County, Ca.lii:ornia., 2z April 975, lemon leaves, Ian Moore collector.This is the/rst description of a pupa .of a member o: this genus.

Osmeterial Glands
Through the transparent integuments o the,.larvae o O. ovi- [ormis there are visible on each side o the area o the osmeterium a pair of tubular coil'ed structures which appear to be connected to the osmeterium by convoluted material.These would seem to be glands so it may be reasonable to call them osmet,e:rial glands.If the osmeterium gives off an offensive odor these could be its source.