Corporate insiders sell their own companies' stock for a number of reasons. 

They might need the cash for a big personal purchase such as a new house or yacht, or they might need the cash to fund a charity. Sometimes they sell as part of a planned selling program that they have put in place for diversification purposes, which allows them to sell stock in stages instead of selling all at one price.

Other times they sell because they think their stock is overvalued and the risk/reward is no longer attractive. Some even dump their own stock because they have inside knowledge that a competitor is eating their lunch and stealing market share. 

But insiders usually buy their own shares for one reason: They think the stock is a bargain and has tremendous upside.

The key word in that last statement is "think." Just because a corporate insider thinks his or her stock is going to trade higher, that doesn't mean it will play out that way. Insiders can have all the conviction in the world that their stock is a buy, but if the market doesn't agree with them, the stock could end up going nowhere. Also, I say "usually" because sometimes insiders are loaned money by the company to buy their own stock. Those loans are often sweetheart deals and shouldn't be viewed as organic insider buying.

At the end of the day, it's institutional money managers running big mutual funds and hedge funds that drive stock prices, not insiders. That said, many of these savvy stock operators will follow insider buying activity when they agree with the insider that the stock is undervalued and has upside potential. This is why it's so important to always be monitoring insider activity but twice as important to make sure the trend of the stock coincides with the insider buying.

Recently, a number of companies' corporate insiders have bought large amounts of stock. These insiders are finding some value in the market, which warrants a closer look at these stocks.

Tangoe

One technology player that insiders are loading up on here is Tangoe (TNGO) , which provides connection lifecycle management software and related services to enterprises and service providers worldwide. Insiders are buying this stock into major weakness, since shares have dropped sharply by 47.8% over the last six months.

Tangoe has a market cap of $276 million and an enterprise value of $212 million. This stock trades at a premium valuation, with a forward price-to-earnings of 18.2. Its estimated growth rate for this year is -42.9%, and for next year it's pegged at -5%. This is not a cash-rich company, since the total cash position on its balance sheet is $36.56 million and its total debt is $5.04 million.

A beneficial owner just bought 2,557,478 shares, or about $18.31 million worth of stock, at $7.16 per share.

From a technical perspective, Tangoe is currently trending below both its 50-day and 200-day moving averages, which is bearish. This stock is spiking notably higher on Wednesday with decent upside volume flows. This move to the upside is now quickly pushing shares of Tangoe within range of triggering a near-term breakout trade above some key overhead resistance levels.

If you're bullish on Tangoe, then I would look for long-biased trades as long as this stock is trending above $6.50 a share and then once it breaks out above both its 20-day moving average of $7.59 and its 50-day moving average of $7.66 a share with high volume. Look for a sustained move or close above those levels with volume that hits near or above its three-month average action of 384,585 shares. If that breakout takes hold soon, then this stock will set up to re-fill some of its previous gap-down-day zone that started near $8.80 a share. Any high-volume move above $8.80 would then give this stock a chance to attack another gap-down-day zone from August that started near $11.50 a share.

Hershey

Another stock that insider are in love with here is Hershey (HSY) - Get Report , which manufactures, imports, markets, distributes and sells confectionery products. Insiders are buying this stock into notable weakness, since shares have fallen by 10.8% over the last six months.

Hershey has a market cap of $18.4 billion and an enterprise value of $20.8 billion. This stock trades at a fair valuation, with a trailing price-to-earnings of 37.5 and a forward price-to-earnings of 19.1. Its estimated growth rate for this year is 3%, and for next year it's pegged 8%. This is not a cash-rich company, since the total cash position on its balance sheet is $343.91 billion and its total debt is $2.77 billion. This stock currently sports a dividend yield of 2.7%.

A beneficial owner just bought 190,000 shares, or about $15.92 million worth of stock, at $83.82 per share.

From a technical perspective, Hershey is currently trending below both its 50-day and 200-day moving averages, which is bearish. This stock has been downtrending badly over the last month and change, with shares falling sharply off its high of $97.40 to its recent low of $83.04 a share. During that downtrend, shares of Hershey have been consistently making lower highs and lower lows, which is bearish technical price action. That said, this stock has now started to spike higher off that $83.04 low and it's beginning to move within range of triggering a near-term breakout trade.

If you're in the bull camp on Hershey, then I would look for long-biased trades as long as this stock is trending above its recent low of $83.04 a share and then once it breaks out above some near-term overhead resistance levels at $86 to $87 a share with volume that registers near or above its three-month average action of 1.25 million shares. If that breakout gets started soon, then this stock will set up to re-test or possibly take out its next major overhead resistance levels at its 20-day moving average of $88.22 to its 50-day moving average of $91.38 a share.

SolarCity

One alternative energy player that insiders are active in here is SolarCity (SCTY) , which designs, manufactures, installs, maintains, monitors, leases and sells solar energy systems to residential, commercial, government, and other customers in the U.S. Insiders are buying this stock into massive weakness, since shares have plunged by 56.9% over the last six months.

SolarCity has a market cap of $2.6 billion and an enterprise value of $4.7 billion. This stock trades at a fair valuation, with a price-to-sales of 7.13 and a price-to-book of 3.11. Its estimated growth rate for this year is -108.5%, and for next year it's pegged at -7%. This is not a cash-rich company, since the total cash position on its balance sheet is $418.37 million and its total debt is $2.45 billion.

A director just bought 198,615 shares, or about $5.25 million worth of stock, at $26.45 per share. That same director also just bought 307,152 shares, or about $7.78 million worth of stock, at $25.20 to $25.40 per share.

From a technical perspective, SolarCity is currently trending below both its 50-day and 200-day moving averages, which is bearish. This stock has been downtrending badly over the last three months and change, with shares falling sharply off its high of $61.72 to its recent low of $24.07 a share. During that downtrend, shares of SolarCity have been consistently making lower highs and lower lows, which is bearish technical price action. That said, this stock has now started to spike higher off that $24.07 low and it's beginning to move within range of triggering a near-term breakout trade.

If you're bullish on SolarCity, then I would look for long-biased trades as long as this stock is trending above its recent low of $24.07 a share and then once it breaks out above some near-term overhead resistance levels at $28 to $28.11 a share with high volume. Look for a sustained move or close above those levels with volume that hits near or above its three-month average volume of 3.55 million shares.

If that breakout hits soon, then this stock will set up to retest or possibly take out its next major overhead resistance levels at its 20-day moving average of $31.07 to $31.89 a share. Any high-volume move above those levels will then give this stock a chance to re-fill some of its previous gap-down-day zone from October that started near $40 a share.

Aegerion Pharmaceuticals

A biotechnology stock that insiders are jumping into here is Aegerion Pharmaceuticals (AEGR) , which develops and commercializes therapies for patients with debilitating rare diseases in the U.S. Insiders are buying this stock into large weakness, since shares have dropped sharply by 48.7% over the last six months.

Aegerion Pharmaceuticals has a market cap of $288 million and an enterprise value of $471 million. This stock trades at a reasonable valuation, with a price-to-sales of 1.13 and a price-to-book of 1.89. Its estimated growth rate for this year -47.4%, and for next year it's pegged at 23.6%. This is not a cash-rich company, since the total cash position on its balance sheet is $71.74 million and its total debt is $253.96 million.

A beneficial owner just bought 40,100 shares, or about $439,000 worth of stock, at $10.96 per share.

From a technical perspective, Aegerion Pharmaceuticals is currently trending below both its 50-day and 200-day moving averages, which is bearish. This stock has been downtrending badly over the last few weeks, with shares falling off its high of $16.63 to its recent low of $8.89 a share. During that downtrend, shares of Aegerion Pharmaceuticals have been consistently making lower highs and lower lows, which is bearish technical price action. That said, this stock has now started to bounce off that $8.89 low and it's now quickly moving within range of triggering a near-term breakout trade.

If you're bullish on Aegerion Pharmaceuticals, then I would look for long-biased trades as long as this stock is trending above its recent low of $8.89 a share and then once it breaks out above some near-term overhead resistance levels at $10.34 to $11.23 a share with high volume. Look for a sustained move or close above those levels with volume that registers near or above its three-month average action of 790,308 shares. If that breakout fires off soon, then this stock will set up to retest or possibly take out its next major overhead resistance levels at $12 to its 20-day moving average of $13.37 a share.

Pozen

One final stock with some large insider buying is pharmaceutical player Pozen (POZN) , which develops products for the treatment of acute and chronic pain, and pain-related conditions in the U.S. and internationally. Insiders are buying this stock into notable weakness, since shares have dropped by 23.5% over the last three months.

Pozen has a market cap of $234 million and an enterprise value of $198 million. This stock trades at a premium valuation, with a forward price-to-earnings of 238. Its estimated growth rate for this year is -123.3%, and for next year it's pegged at 121.4%. This is a cash-rich company, since the total cash position on its balance sheet is $36.99 million and its total debt is zero.

The CEO just bought 1,000,000 shares, or about $6.55 million worth of stock, at $6.55 per share. From a technical perspective, Pozen is currently trending above its 50-day moving average and below its 200-day moving average, which is neutral trendwise. This stock has been uptrending over the last month and change, with shares moving higher from its low of $5.49 to its recent high of $7.23 a share. During that uptrend, this stock has been making mostly higher lows and higher highs, which is bullish technical price action.

If you're bullish on Pozen, then I would look for long-biased trades as long as this stock is trending above its 20-day moving average of $6.40 a share and then once it breaks out above some near-term overhead resistance at $7.50 a share with high volume. Look for a sustained move or close above that level with volume that hits near or above its three-month average volume of 545,502 shares. If that breakout triggers soon, then this stock will set up to retest or possibly take out its next major overhead resistance levels at its 200-day moving average of $8.23 to $9, or even $9.50 a share.

Disclosure: This article is commentary by an independent contributor. At the time of publication, the author held no positions in the stocks mentioned.