This study was supported by the major scientific and technological innovation project (2020CXGC010802).

NOTE: Pay attention to safety measurements before trapping wild-type migratory insects, it is suggested to wear safety gear (gloves, long-sleeved shirts, and goggles). Also, turn off the trap when not in use to avoid other safety hazards and overheating the light. It is important to follow safety protocols before dissection, such as wearing gloves, goggles, and lab coat to prevent exposure to body fluids and chemicals.
1. Trapping of migrant insects
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	<li>Begin this prot...

Dissection for Identifying Migratory Insects via Ovarian Reproductive Analysis

Ovarian analysis methods are routinely used in plant protection, to elucidate the movement of insect flight and population for forecasting19,20,21 and to elaborate on the physiological variations in insects. It has been noticed that the unique migration and rapid dispersion ability of common agricultural pests, such as bollworm, armyworm, taro caterpillar,&#160;and beet moth, make it difficult for prediction from other regions. ...

Migration of insects plays a vital role in population dynamics of global insect distribution for insects like Helicoverpa armigera - the cotton bollworm, Mythimna separate - the oriental armyworm, Spodoptera litura - the taro caterpillar, Spodoptera exigua - the beet armyworm, that have been reported as serious pests in China1,2,3,4. The long travel distances, seasonal movements, high fecundity of migratory pests, and ecological factors have brought great difficulties in the prediction, forecast, and control of these pests5. Pest migration monitoring is required to reveal the adaptability and behavioral changes that facilitate migratory pests according to climate changes or cycles6. To sustain their growth, reproduction, and survival, insects have acquired sequential adaptability during evolution; this series of adaptive life has generated many changes in the reproductive system, such as migratory strategy leading to control of ovarian development in the long migratory process.
Ovarian development is common in migratory pests, which affects the growth of their population7. Therefore, ovarian development has been a hot topic of migratory pest research for a long time. A series of studies have led to several ovarian development indicators and classification strategies. Until now, several methods have been used to analyze ovary development, e.g., Loxostege sticticalis - the meadow moth- ovary development which includes the initial feathering stage, the early spawning period, the spawning period, and the end of oviposition8. Some researchers divide ovarian levels on the bases of yolk color development in migratory Lepidopteran pests, such as S. exigua - the beet armyworm, Pseudaletia unipuncta - the true armyworm, and Cnaphalocrocis medinalis- the rice leaf-folder, etc.9,10,11,12. In previous studies, the ovarian development levels for pests, such as cotton bollworm and rice leaf roller, were divided into five stages: yolk deposition stage, egg grain maturity stage, mature waiting for birth, peak ovogenesis period, and end spawning stage13,14. The ovarian development of the European corn borer was divided into six developmental stages: yolk deposition stage, egg maturation, pre-eggs dispositioning, peak spawning stage, and end-spawning stage15.
Moreover, insects of the same genus have different stages of development, such as ovarian development levels of Spodoptera frugiperda - the fall armyworm - falls into four levels: yolk deposition stage, mature waiting for delivery, peak ovi-positivity, and end spawning stage16. On the other hand, ovarian development in Spodoptera exigua - the beet moth - has five levels: transparent, vitellogenesis, maturation of eggs, egg release, and late egg-laying levels17.
Former studies can only classify development from single to multiple ovarian development levels using color maturity of yolk, oviposition, and egg developments, but classification cannot be done based on anatomy of the reproductive system. The development of an ovary based on the morphogenesis anatomy is a less studied area. Here, the dissection method was designed to predict migratory females in the population using two ovarian tissue types, to elaborate their reproductive dynamics based on the anatomical morphogenesis of -ovarian development stage and mating sac- providing direct evidence to distinguish migratory wild-type females.
Some studies have found that, migratory Noctuidae insect species were frequently captured by searchlights18. The ovary of most migratory Noctuidae insect species is in the early stages of development during the initial stage of migration and the ovarian level increases with the migratory progress. In this study, the dissection method for ovarian development grades is described, to study the two reproductive tissues of different female population pests, captured by search light. This method not only advances the research to understand the migratory dynamics, but also facilities in insect classification, insect physiology study, pest prediction, and forecasting of female pest species.

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	<tbody>
		<tr>
			<td>Digital camera</td>
			<td>Canon ( China ) co., LTD</td>
			<td>EOS 800D</td>
			<td></td>
		</tr>
		<tr>
			<td>Dropper</td>
			<td>Qingdao jindian biochemical equipment co., LTD</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Ethanol absolute (99.7%)</td>
			<td>Shanghai Hushi Laboratory Equipmentco., LTD</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Forceps</td>
			<td>&#160;Vetus Tools co., LTD</td>
			<td>ST-14</td>
			<td></td>
		</tr>
		<tr>
			<td>GT75 type halogen headlamp (1000 W)</td>
			<td>Shanghai Yadeng Industry co., LTD</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Helicoverpa armigera, Mythimna separate, Spodoptera litura, Spodoptera exigua</td>
			<td>Jiyang district, Jinan city, Shandong province, China</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Measuring cylinder, beaker, flask</td>
			<td>Qingdao jindian biochemical equipment co., LTD</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Net bag&#160;</td>
			<td>Qingdao jindian biochemical equipment co., LTD</td>
			<td></td>
			<td>0.5 m&#160;</td>
		</tr>
		<tr>
			<td>Net cages&#160;</td>
			<td>Qingdao jindian biochemical equipment co., LTD</td>
			<td></td>
			<td>30 cm x 30 cm</td>
		</tr>
		<tr>
			<td>Petri dishes</td>
			<td>Qingdao jindian biochemical equipment co., LTD</td>
			<td></td>
			<td>&#160;60 mm diameter</td>
		</tr>
	</tbody>
</table>

dissection and grading of ovarian development in wild-type female insects

Migratory insect pests pose serious challenges to food production and security all over the world. The migratory pests can be monitored and captured using searchlight traps. One of the most important techniques for migratory pest forecasting is to identify the migratory species. However, in most cases, it is difficult to get the information just by appearance. Therefore, using knowledge acquired by systematic analysis of the female reproductive system can help to understand the combined anatomic morphology of the ovarian mating sac and ovary developmental grading of wild-type migratory insects captured with searchlight traps. To demonstrate the applicability of this method, ovarian development status and egg grain development stages were directly assessed in Helicoverpa armigera, Mythimna separata, Spodoptera litura, and Spodoptera exigua for the ovarian anatomy, and the ovarian mating sacs were studied in Agrotis ipsilon, Spaelotis valida, Helicoverpa armigera, Athetis lepigone, Mythimna separata, Spodoptera litura, Mamestra brassicae, and Spodoptera exigua, to explore their relationships. This work shows the specific dissection method to predict wild-type migratory insects, comparing the unique reproductive system of different migratory insects. Then, both tissues, namely, the ovary and mating sacs, were further investigated. This method helps to predict the dynamics and the structural development of reproductive systems in wild-type female migratory insects.

Author Spotlight: Analysis of Ovarian Anatomy in Migratory Insects to Overcome Experimental Challenges 

Dissection and Grading of Ovarian Development in Wild-Type Female Insects

We aim to apply easy and this newest method for migratory pest, in describing the ovarian anatomy of migratory females. This information will be useful to analyze similar individual species. To predict migratory female insects is pretty challenging.Therefore, visualization of ovarian anatomy is quite easy and very useful.

Development of the eggs 
The above protocol was applied to analyze the development of eggs in the ovary. For this purpose, firstly, eggs were classified generally into four stages to distinguish early and mature stage of egg development among all species e.g., bollworm, armyworm, taro caterpillar, and beet moth. Here, the early stage of feathering (milky white transparent stage) was observed. Figure 2A shows that ovaries have not yet begun to develop, the ovarian duct i...

Watch this Scientific Journal Video about Analysis of Ovarian Anatomy in Migratory Insects to Overcome Experimental Challenges at JoVE.com

The protocol demonstrates a simple and easy dissection method, suitable for wild-type migratory female insects captured with searchlight traps. This technique can significantly clarify the same species by comparing both reproductive tissues, namely the mating sac and ovarian development of wild-type female insects.

Migratory insect pests pose serious challenges to food production and security all over the world. The migratory pests can be monitored and captured using ...