Therophilus javanus

3.1. General Morphology of Therophilus javanus Female Reproductive System.

The T. javanus female reproductive system consisted of a pair of globular-shaped ovaries housing several ovarioles, a spermatheca, a Dufour’s gland, a venom gland, composed of a venom duct and two venom gland filaments, and the wasp ovipositor ( Figure 2 View FIGURE 2 ).

3.2. Impact of Host Quality on the Number of Ovarioles per Female. The mean number of ovarioles per female was found to be significantly influenced by host age at the moment of oviposition (GLM: 𝜒 2 = 3.6358, df =2, 𝑝<0.05) ( Figure 3 View FIGURE 3 ). In general, the number of ovarioles varied between the three females categories and was increased as the host caterpillar increased in size at the moment of oviposition. The average count in one-day-old females emerging from L1 two days old, L1 three days old, and L2 four days old is 38.36 ± 4.42 (𝑛=31); 38.16 ± 3.20 (𝑛=31); and 40.87 ± 3.15 (𝑛=31), respectively.

3.3. Egg Development within the Ovariole. Therophilus javanus ovarioles belong to the polytrophic meroistic type. Egg development occurred anteriorly to posteriorly along the ovariole, with two distinctly recognizable regions: the germarium and the vitellarium. The germarium contained a number of spherical cells observed as either free or clustered ( Figure 4 View FIGURE 4 (a)). Cell nuclei size increased as they progressed along the germarium. The vitellarium is the posterior region of the ovariole, where egg chambers (follicles) are formed and grown. In T. javanus vitellarium, nurse cells were disposed at the top of the oocyte, all being surrounded by a sheath composed of follicular cells ( Figure 4 View FIGURE 4 (b)). During progression of the follicles from the anterior to the posterior part of the vitellarium, vitellogenesis takes place and the size of the oocyte increases ( Figure 4 View FIGURE 4 (c)). A cross-section of the entire ovary shows that egg chambers were in different maturation stages within and between ovarioles ( Figure 4 View FIGURE 4 (d)). Well-differentiated oocytes (with chorion) displayed an ovoid shaped form and had a slender tapering stalk at their posterior end. Mature eggs measured 160.9 ± 6.9 𝜇m (𝑛=20) in length with widths ranging from 25.3 ± 2.6 𝜇m (𝑛=20) (anterior pole) to 9.4 ± 1.3 𝜇m (𝑛=20) (posterior/basal pole) ( Figure 4 View FIGURE 4 (e)).

3.4. Impact of T. javanus Female Age on the Number of Eggs. The number of eggs (both immature and mature) per female ranged from 1 to 88 and from 349 to 476 in 12-hour-old and 72-hour-old females, respectively. The overall mean number per female increased with the female age (GLM: 𝜒 2 = 6481.2, df = 1, 𝑝 <0.001). The number of eggs ranged from 0 to 6 and from 3 to 21 per ovariole, 12 hours and 72 hours after female emergence, respectively ( Table 1 View TABLE 1 ). As expected, the number of eggs per female was found to be significantly influenced by the total number of ovariole per female (GLM: 𝜒 2 = 233.4, df =1, 𝑝<0.001).

3.5. Impact of Host and Female Wasp Age on the Egg Load. Overall, the mean number of mature eggs per female was found to be significantly influenced by host age (GLM: 𝜒 2 = 44.4, df = 1, 𝑝 <0.001) and parasitoid female age (GLM: 𝜒 2 = 16600.9, df = 4, 𝑝<0.001). Females that emerged from four-day-old host caterpillar at oviposition had a higher mean number of mature eggs. ( Figure 5 View FIGURE 5 ).